On Thu, 2020-12-17 at 17:59 +0800, Liu Ying wrote:
> This patch adds a drm bridge driver for i.MX8qxp LVDS display bridge(LDB).
> The LDB has two channels.  Each of them supports up to 24bpp parallel
> input color format and can map the input to VESA or JEIDA standards.
> The two channels cannot be used simultaneously, that is to say, the user
> should pick one of them to use.  Two LDB channels from two LDB instances
> can work together in LDB split mode to support a dual link LVDS display.
> The channel indexes have to be different.  Channel0 outputs odd pixels
> and channel1 outputs even pixels.  This patch supports the LDB single
> mode and split mode.
> 
> Signed-off-by: Liu Ying <victor....@nxp.com>
> ---
>  drivers/gpu/drm/bridge/imx/Kconfig       |  10 +
>  drivers/gpu/drm/bridge/imx/Makefile      |   1 +
>  drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c | 762 
> +++++++++++++++++++++++++++++++
>  3 files changed, 773 insertions(+)
>  create mode 100644 drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c
> 
> diff --git a/drivers/gpu/drm/bridge/imx/Kconfig 
> b/drivers/gpu/drm/bridge/imx/Kconfig
> index 23e24fd..2a32ad3 100644
> --- a/drivers/gpu/drm/bridge/imx/Kconfig
> +++ b/drivers/gpu/drm/bridge/imx/Kconfig
> @@ -6,6 +6,16 @@ config DRM_IMX_LVDS_BRIDGE_HELPER
>         Helper to support Freescale i.MX LVDS Display Bridge(LDB).
>         This bridge is embedded in a SoC.
>  
> +config DRM_IMX8QXP_LDB
> +     tristate "Freescale i.MX8QXP LVDS display bridge"
> +     depends on DRM_IMX_LVDS_BRIDGE_HELPER
> +     depends on OF
> +     depends on COMMON_CLK
> +     select DRM_KMS_HELPER
> +     help
> +       Choose this to enable the internal LVDS Display Bridge(LDB) found in
> +       Freescale i.MX8qxp processor.
> +
>  config DRM_IMX8QXP_PIXEL_COMBINER
>       tristate "Freescale i.MX8QM/QXP pixel combiner"
>       depends on OF
> diff --git a/drivers/gpu/drm/bridge/imx/Makefile 
> b/drivers/gpu/drm/bridge/imx/Makefile
> index 902b703..13160f0 100644
> --- a/drivers/gpu/drm/bridge/imx/Makefile
> +++ b/drivers/gpu/drm/bridge/imx/Makefile
> @@ -1,4 +1,5 @@
>  obj-$(CONFIG_DRM_IMX_LVDS_BRIDGE_HELPER) += imx-ldb-helper.o
> +obj-$(CONFIG_DRM_IMX8QXP_LDB) += imx8qxp-ldb.o
>  obj-$(CONFIG_DRM_IMX8QXP_PIXEL_COMBINER) += imx8qxp-pixel-combiner.o
>  obj-$(CONFIG_DRM_IMX8QXP_PIXEL_LINK) += imx8qxp-pixel-link.o
>  obj-$(CONFIG_DRM_IMX8QXP_PIXEL_LINK_TO_DPI) += imx8qxp-pxl2dpi.o
> diff --git a/drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c 
> b/drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c
> new file mode 100644
> index 00000000..318615fb
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c
> @@ -0,0 +1,762 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +
> +/*
> + * Copyright 2020 NXP
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/mfd/syscon.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/of_graph.h>
> +#include <linux/phy/phy.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/regmap.h>
> +
> +#include <drm/bridge/imx_ldb_helper.h>
> +#include <drm/drm_atomic_state_helper.h>
> +#include <drm/drm_bridge.h>
> +#include <drm/drm_connector.h>
> +#include <drm/drm_fourcc.h>
> +#include <drm/drm_of.h>
> +#include <drm/drm_print.h>
> +
> +#define  LDB_CH_SEL          (1 << 28)
> +
> +#define SS_CTRL                      0x20
> +#define  CH_HSYNC_M(id)              BIT(0 + ((id) * 2))
> +#define  CH_VSYNC_M(id)              BIT(1 + ((id) * 2))
> +#define  CH_PHSYNC(id)               BIT(0 + ((id) * 2))
> +#define  CH_PVSYNC(id)               BIT(1 + ((id) * 2))
> +
> +#define DRIVER_NAME          "imx8qxp-ldb"
> +
> +struct imx8qxp_ldb_channel {
> +     struct ldb_channel base;
> +     struct phy *phy;
> +     unsigned int di_id;
> +};
> +
> +struct imx8qxp_ldb {
> +     struct ldb base;
> +     struct device *dev;
> +     struct imx8qxp_ldb_channel channel[MAX_LDB_CHAN_NUM];
> +     struct clk *clk_pixel;
> +     struct clk *clk_bypass;
> +     struct drm_bridge *companion;
> +     int active_chno;
> +};
> +
> +static inline struct imx8qxp_ldb_channel *
> +base_to_imx8qxp_ldb_channel(struct ldb_channel *base)
> +{
> +     return container_of(base, struct imx8qxp_ldb_channel, base);
> +}
> +
> +static inline struct imx8qxp_ldb *base_to_imx8qxp_ldb(struct ldb *base)
> +{
> +     return container_of(base, struct imx8qxp_ldb, base);
> +}
> +
> +static void imx8qxp_ldb_set_phy_cfg(struct imx8qxp_ldb *imx8qxp_ldb,
> +                                 unsigned long di_clk, bool is_split,
> +                                 struct phy_configure_opts_lvds *phy_cfg)
> +{
> +     phy_cfg->bits_per_lane_and_dclk_cycle = 7;
> +     phy_cfg->lanes = 4;
> +
> +     if (is_split) {
> +             phy_cfg->differential_clk_rate = di_clk / 2;
> +             phy_cfg->is_slave = !imx8qxp_ldb->companion;
> +     } else {
> +             phy_cfg->differential_clk_rate = di_clk;
> +             phy_cfg->is_slave = false;
> +     }
> +}
> +
> +static int imx8qxp_ldb_bridge_atomic_check(struct drm_bridge *bridge,
> +                                struct drm_bridge_state *bridge_state,
> +                                struct drm_crtc_state *crtc_state,
> +                                struct drm_connector_state *conn_state)
> +{
> +     struct ldb_channel *ldb_ch = bridge->driver_private;
> +     struct ldb *ldb = ldb_ch->ldb;
> +     struct imx8qxp_ldb_channel *imx8qxp_ldb_ch =
> +                                     base_to_imx8qxp_ldb_channel(ldb_ch);
> +     struct imx8qxp_ldb *imx8qxp_ldb = base_to_imx8qxp_ldb(ldb);
> +     struct drm_bridge *companion = imx8qxp_ldb->companion;
> +     struct drm_display_mode *adj = &crtc_state->adjusted_mode;
> +     unsigned long di_clk = adj->clock * 1000;
> +     bool is_split = ldb_channel_is_split_link(ldb_ch);
> +     union phy_configure_opts opts = { };
> +     struct phy_configure_opts_lvds *phy_cfg = &opts.lvds;
> +     int ret;
> +
> +     ret = ldb_bridge_atomic_check_helper(bridge, bridge_state,
> +                                             crtc_state, conn_state);
> +     if (ret)
> +             return ret;
> +
> +     imx8qxp_ldb_set_phy_cfg(imx8qxp_ldb, di_clk, is_split, phy_cfg);
> +     ret = phy_validate(imx8qxp_ldb_ch->phy, PHY_MODE_LVDS, 0, &opts);
> +     if (ret < 0) {
> +             DRM_DEV_DEBUG_DRIVER(imx8qxp_ldb->dev,
> +                                  "failed to validate PHY: %d\n", ret);
> +             return ret;
> +     }
> +
> +     if (is_split && companion) {
> +             ret = companion->funcs->atomic_check(companion,
> +                                     bridge_state, crtc_state, conn_state);
> +             if (ret)
> +                     return ret;
> +     }
> +
> +     return ret;
> +}
> +
> +static void
> +imx8qxp_ldb_bridge_mode_set(struct drm_bridge *bridge,
> +                         const struct drm_display_mode *mode,
> +                         const struct drm_display_mode *adjusted_mode)
> +{
> +     struct ldb_channel *ldb_ch = bridge->driver_private;
> +     struct ldb_channel *companion_ldb_ch;
> +     struct ldb *ldb = ldb_ch->ldb;
> +     struct imx8qxp_ldb_channel *imx8qxp_ldb_ch =
> +                                     base_to_imx8qxp_ldb_channel(ldb_ch);
> +     struct imx8qxp_ldb *imx8qxp_ldb = base_to_imx8qxp_ldb(ldb);
> +     struct drm_bridge *companion = imx8qxp_ldb->companion;
> +     struct device *dev = imx8qxp_ldb->dev;
> +     unsigned long di_clk = adjusted_mode->clock * 1000;
> +     bool is_split = ldb_channel_is_split_link(ldb_ch);
> +     union phy_configure_opts opts = { };
> +     struct phy_configure_opts_lvds *phy_cfg = &opts.lvds;
> +     u32 chno = ldb_ch->chno;
> +     int ret;
> +
> +     ret = pm_runtime_get_sync(dev);
> +     if (ret < 0)
> +             DRM_DEV_ERROR(dev, "failed to get runtime PM sync: %d\n", ret);
> +
> +     ret = phy_init(imx8qxp_ldb_ch->phy);
> +     if (ret < 0)
> +             DRM_DEV_ERROR(dev, "failed to initialize PHY: %d\n", ret);
> +
> +     ret = phy_set_mode(imx8qxp_ldb_ch->phy, PHY_MODE_LVDS);
> +     if (ret < 0)
> +             DRM_DEV_ERROR(dev, "failed to set PHY mode: %d\n", ret);
> +
> +     if (is_split && companion) {
> +             companion_ldb_ch = bridge_to_ldb_ch(companion);
> +
> +             companion_ldb_ch->in_bus_format = ldb_ch->in_bus_format;
> +             companion_ldb_ch->out_bus_format = ldb_ch->out_bus_format;
> +     }
> +
> +     clk_set_rate(imx8qxp_ldb->clk_bypass, di_clk);
> +     clk_set_rate(imx8qxp_ldb->clk_pixel, di_clk);
> +
> +     imx8qxp_ldb_set_phy_cfg(imx8qxp_ldb, di_clk, is_split, phy_cfg);
> +     ret = phy_configure(imx8qxp_ldb_ch->phy, &opts);
> +     if (ret < 0)
> +             DRM_DEV_ERROR(dev, "failed to configure PHY: %d\n", ret);
> +
> +     if (chno == 0)
> +             ldb->ldb_ctrl &= ~LDB_CH_SEL;
> +     else
> +             ldb->ldb_ctrl |= LDB_CH_SEL;
> +
> +     /* input VSYNC signal from pixel link is active low */
> +     if (imx8qxp_ldb_ch->di_id == 0)
> +             ldb->ldb_ctrl |= LDB_DI0_VS_POL_ACT_LOW;
> +     else
> +             ldb->ldb_ctrl |= LDB_DI1_VS_POL_ACT_LOW;
> +
> +     /*
> +      * For split mode, settle input VSYNC signal polarity and
> +      * channel selection down early.
> +      */
> +     if (is_split)
> +             regmap_write(ldb->regmap, ldb->ctrl_reg, ldb->ldb_ctrl);
> +
> +     ldb_bridge_mode_set_helper(bridge, mode, adjusted_mode);
> +
> +     if (adjusted_mode->flags & DRM_MODE_FLAG_NVSYNC)
> +             regmap_update_bits(ldb->regmap, SS_CTRL, CH_VSYNC_M(chno), 0);
> +     else if (adjusted_mode->flags & DRM_MODE_FLAG_PVSYNC)
> +             regmap_update_bits(ldb->regmap, SS_CTRL,
> +                                CH_VSYNC_M(chno), CH_PVSYNC(chno));
> +
> +     if (adjusted_mode->flags & DRM_MODE_FLAG_NHSYNC)
> +             regmap_update_bits(ldb->regmap, SS_CTRL, CH_HSYNC_M(chno), 0);
> +     else if (adjusted_mode->flags & DRM_MODE_FLAG_PHSYNC)
> +             regmap_update_bits(ldb->regmap, SS_CTRL,
> +                                CH_HSYNC_M(chno), CH_PHSYNC(chno));
> +
> +     if (is_split && companion)
> +             companion->funcs->mode_set(companion, mode, adjusted_mode);
> +}
> +
> +static void
> +imx8qxp_ldb_bridge_atomic_pre_enable(struct drm_bridge *bridge,
> +                                  struct drm_bridge_state *old_bridge_state)
> +{
> +     struct ldb_channel *ldb_ch = bridge->driver_private;
> +     struct ldb *ldb = ldb_ch->ldb;
> +     struct imx8qxp_ldb *imx8qxp_ldb = base_to_imx8qxp_ldb(ldb);
> +     struct drm_bridge *companion = imx8qxp_ldb->companion;
> +     bool is_split = ldb_channel_is_split_link(ldb_ch);
> +
> +     clk_prepare_enable(imx8qxp_ldb->clk_pixel);
> +     clk_prepare_enable(imx8qxp_ldb->clk_bypass);
> +
> +     if (is_split && companion)
> +             companion->funcs->atomic_pre_enable(companion, 
> old_bridge_state);
> +}
> +
> +static void
> +imx8qxp_ldb_bridge_atomic_enable(struct drm_bridge *bridge,
> +                              struct drm_bridge_state *old_bridge_state)
> +{
> +     struct ldb_channel *ldb_ch = bridge->driver_private;
> +     struct ldb *ldb = ldb_ch->ldb;
> +     struct imx8qxp_ldb_channel *imx8qxp_ldb_ch =
> +                                     base_to_imx8qxp_ldb_channel(ldb_ch);
> +     struct imx8qxp_ldb *imx8qxp_ldb = base_to_imx8qxp_ldb(ldb);
> +     struct drm_bridge *companion = imx8qxp_ldb->companion;
> +     struct device *dev = imx8qxp_ldb->dev;
> +     bool is_split = ldb_channel_is_split_link(ldb_ch);
> +     int ret;
> +
> +     if (ldb_ch->chno == 0 || is_split) {
> +             ldb->ldb_ctrl &= ~LDB_CH0_MODE_EN_MASK;
> +             ldb->ldb_ctrl |= imx8qxp_ldb_ch->di_id == 0 ?
> +                             LDB_CH0_MODE_EN_TO_DI0 : LDB_CH0_MODE_EN_TO_DI1;
> +     }
> +     if (ldb_ch->chno == 1 || is_split) {
> +             ldb->ldb_ctrl &= ~LDB_CH1_MODE_EN_MASK;
> +             ldb->ldb_ctrl |= imx8qxp_ldb_ch->di_id == 0 ?
> +                             LDB_CH1_MODE_EN_TO_DI0 : LDB_CH1_MODE_EN_TO_DI1;
> +     }
> +
> +     ldb_bridge_enable_helper(bridge);
> +
> +     ret = phy_power_on(imx8qxp_ldb_ch->phy);
> +     if (ret)
> +             DRM_DEV_ERROR(dev, "failed to power on PHY: %d\n", ret);
> +
> +     if (is_split && companion)
> +             companion->funcs->atomic_enable(companion, old_bridge_state);
> +}
> +
> +static void
> +imx8qxp_ldb_bridge_atomic_disable(struct drm_bridge *bridge,
> +                               struct drm_bridge_state *old_bridge_state)
> +{
> +     struct ldb_channel *ldb_ch = bridge->driver_private;
> +     struct ldb *ldb = ldb_ch->ldb;
> +     struct imx8qxp_ldb_channel *imx8qxp_ldb_ch =
> +                                     base_to_imx8qxp_ldb_channel(ldb_ch);
> +     struct imx8qxp_ldb *imx8qxp_ldb = base_to_imx8qxp_ldb(ldb);
> +     struct drm_bridge *companion = imx8qxp_ldb->companion;
> +     struct device *dev = imx8qxp_ldb->dev;
> +     bool is_split = ldb_channel_is_split_link(ldb_ch);
> +     int ret;
> +
> +     ret = phy_power_off(imx8qxp_ldb_ch->phy);
> +     if (ret)
> +             DRM_DEV_ERROR(dev, "failed to power off PHY: %d\n", ret);
> +
> +     ret = phy_exit(imx8qxp_ldb_ch->phy);
> +     if (ret < 0)
> +             DRM_DEV_ERROR(dev, "failed to teardown PHY: %d\n", ret);
> +
> +     ldb_bridge_disable_helper(bridge);
> +
> +     clk_disable_unprepare(imx8qxp_ldb->clk_bypass);
> +     clk_disable_unprepare(imx8qxp_ldb->clk_pixel);
> +
> +     if (is_split && companion)
> +             companion->funcs->atomic_disable(companion, old_bridge_state);
> +
> +     ret = pm_runtime_put(dev);
> +     if (ret < 0)
> +             DRM_DEV_ERROR(dev, "failed to put runtime PM: %d\n", ret);
> +}
> +
> +static const u32 imx8qxp_ldb_bus_output_fmts[] = {
> +     MEDIA_BUS_FMT_RGB666_1X7X3_SPWG,
> +     MEDIA_BUS_FMT_RGB888_1X7X4_SPWG,
> +     MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA,
> +     MEDIA_BUS_FMT_FIXED,
> +};
> +
> +static bool imx8qxp_ldb_bus_output_fmt_supported(u32 fmt)
> +{
> +     int i;
> +
> +     for (i = 0; i < ARRAY_SIZE(imx8qxp_ldb_bus_output_fmts); i++) {
> +             if (imx8qxp_ldb_bus_output_fmts[i] == fmt)
> +                     return true;
> +     }
> +
> +     return false;
> +}
> +
> +static u32 *
> +imx8qxp_ldb_bridge_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
> +                                     struct drm_bridge_state *bridge_state,
> +                                     struct drm_crtc_state *crtc_state,
> +                                     struct drm_connector_state *conn_state,
> +                                     u32 output_fmt,
> +                                     unsigned int *num_input_fmts)
> +{
> +     struct drm_display_info *di;
> +     const struct drm_format_info *finfo;
> +     u32 *input_fmts;
> +
> +     if (!imx8qxp_ldb_bus_output_fmt_supported(output_fmt))
> +             return NULL;
> +
> +     *num_input_fmts = 1;
> +
> +     input_fmts = kmalloc(sizeof(*input_fmts), GFP_KERNEL);
> +     if (!input_fmts)
> +             return NULL;
> +
> +     switch (output_fmt) {
> +     case MEDIA_BUS_FMT_FIXED:
> +             di = &conn_state->connector->display_info;
> +
> +             /*
> +              * Look at the first bus format to determine input format.
> +              * Default to MEDIA_BUS_FMT_RGB888_1X24, if no match.
> +              */
> +             if (di->num_bus_formats) {
> +                     finfo = drm_format_info(di->bus_formats[0]);
> +
> +                     input_fmts[0] = finfo->depth == 18 ?
> +                                     MEDIA_BUS_FMT_RGB666_1X24_CPADHI :
> +                                     MEDIA_BUS_FMT_RGB888_1X24;
> +             } else {
> +                     input_fmts[0] = MEDIA_BUS_FMT_RGB888_1X24;
> +             }
> +             break;
> +     case MEDIA_BUS_FMT_RGB666_1X7X3_SPWG:
> +             input_fmts[0] = MEDIA_BUS_FMT_RGB666_1X24_CPADHI;
> +             break;
> +     case MEDIA_BUS_FMT_RGB888_1X7X4_SPWG:
> +     case MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA:
> +             input_fmts[0] = MEDIA_BUS_FMT_RGB888_1X24;
> +             break;
> +     default:
> +             kfree(input_fmts);
> +             input_fmts = NULL;
> +             break;
> +     }
> +
> +     return input_fmts;
> +}
> +
> +static u32 *
> +imx8qxp_ldb_bridge_atomic_get_output_bus_fmts(struct drm_bridge *bridge,
> +                                     struct drm_bridge_state *bridge_state,
> +                                     struct drm_crtc_state *crtc_state,
> +                                     struct drm_connector_state *conn_state,
> +                                     unsigned int *num_output_fmts)
> +{
> +     *num_output_fmts = ARRAY_SIZE(imx8qxp_ldb_bus_output_fmts);
> +     return kmemdup(imx8qxp_ldb_bus_output_fmts,
> +                     sizeof(imx8qxp_ldb_bus_output_fmts), GFP_KERNEL);
> +}
> +
> +static enum drm_mode_status
> +imx8qxp_ldb_bridge_mode_valid(struct drm_bridge *bridge,
> +                           const struct drm_display_info *info,
> +                           const struct drm_display_mode *mode)
> +{
> +     struct ldb_channel *ldb_ch = bridge->driver_private;
> +     bool is_single = ldb_channel_is_single_link(ldb_ch);
> +
> +     if (mode->clock > 170000)
> +             return MODE_CLOCK_HIGH;
> +
> +     if (mode->clock > 150000 && is_single)
> +             return MODE_CLOCK_HIGH;
> +
> +     return MODE_OK;
> +}
> +
> +static const struct drm_bridge_funcs imx8qxp_ldb_bridge_funcs = {
> +     .atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
> +     .atomic_destroy_state   = drm_atomic_helper_bridge_destroy_state,
> +     .atomic_reset           = drm_atomic_helper_bridge_reset,
> +     .mode_valid             = imx8qxp_ldb_bridge_mode_valid,
> +     .attach                 = ldb_bridge_attach_helper,
> +     .atomic_check           = imx8qxp_ldb_bridge_atomic_check,
> +     .mode_set               = imx8qxp_ldb_bridge_mode_set,
> +     .atomic_pre_enable      = imx8qxp_ldb_bridge_atomic_pre_enable,
> +     .atomic_enable          = imx8qxp_ldb_bridge_atomic_enable,
> +     .atomic_disable         = imx8qxp_ldb_bridge_atomic_disable,
> +     .atomic_get_input_bus_fmts =
> +                     imx8qxp_ldb_bridge_atomic_get_input_bus_fmts,
> +     .atomic_get_output_bus_fmts =
> +                     imx8qxp_ldb_bridge_atomic_get_output_bus_fmts,
> +};
> +
> +static int imx8qxp_ldb_set_di_id(struct imx8qxp_ldb *imx8qxp_ldb)
> +{
> +     struct imx8qxp_ldb_channel *imx8qxp_ldb_ch =
> +                      &imx8qxp_ldb->channel[imx8qxp_ldb->active_chno];
> +     struct ldb_channel *ldb_ch = &imx8qxp_ldb_ch->base;
> +     struct device_node *remote, *port, *ep = NULL;
> +     struct device *dev = imx8qxp_ldb->dev;
> +     struct of_endpoint endpoint;
> +     int ep_cnt;
> +     int ret;
> +
> +     /* remote is PXL2DPI */
> +     remote = of_graph_get_remote_node(ldb_ch->np, 0, 0);
> +     if (!remote) {
> +             DRM_DEV_ERROR(dev, "failed to get PXL2DPI node\n");
> +             return -ENODEV;
> +     }
> +
> +     port = of_graph_get_port_by_id(remote, 0);
> +     if (!port) {
> +             DRM_DEV_ERROR(dev, "failed to get PXL2DPI node's port@0\n");
> +             ret = -ENODEV;
> +             goto out;
> +     }
> +
> +     ep_cnt = of_get_available_child_count(port);
> +     if (ep_cnt == 0) {
> +             DRM_DEV_ERROR(dev,
> +                     "no available endpoints of PXL2DPI node's port@0\n");
> +             ret = -ENODEV;
> +             goto out;
> +     } else if (ep_cnt > 1) {
> +             DRM_DEV_ERROR(dev,
> +                    "invalid available endpoints of PXL2DPI node's 
> port@0\n");
> +             ret = -ENOTSUPP;
> +             goto out;
> +     }
> +
> +     ep = of_get_next_available_child(port, NULL);
> +     if (!ep) {
> +             DRM_DEV_ERROR(dev,
> +               "failed to get available endpoint of PXL2DPI node's 
> port@0\n");
> +             ret = -ENODEV;
> +             goto out;
> +     }

This function is not well written. I'll rewrite it in the next version
by using of_graph_get_endpoint_by_regs()
and of_graph_get_remote_endpoint() to get the remote endpoint.

Liu Ying 

> +
> +     ret = of_graph_parse_endpoint(ep, &endpoint);
> +     if (ret) {
> +             DRM_DEV_ERROR(dev,
> +                 "failed to parse endpoint of PXL2DPI node's port@0: %d\n",
> +                                                                     ret);
> +             goto out;
> +     }
> +
> +     imx8qxp_ldb_ch->di_id = endpoint.id;
> +out:
> +     of_node_put(ep);
> +     of_node_put(port);
> +     of_node_put(remote);
> +
> +     return ret;
> +}
> +
> +static int
> +imx8qxp_ldb_check_chno_and_dual_link(struct ldb_channel *ldb_ch, int link)
> +{
> +     if ((link == DRM_LVDS_DUAL_LINK_ODD_EVEN_PIXELS && ldb_ch->chno != 0) ||
> +         (link == DRM_LVDS_DUAL_LINK_EVEN_ODD_PIXELS && ldb_ch->chno != 1))
> +             return -EINVAL;
> +
> +     return 0;
> +}
> +
> +static int imx8qxp_ldb_parse_dt_companion(struct imx8qxp_ldb *imx8qxp_ldb)
> +{
> +     struct imx8qxp_ldb_channel *imx8qxp_ldb_ch =
> +                      &imx8qxp_ldb->channel[imx8qxp_ldb->active_chno];
> +     struct ldb_channel *ldb_ch = &imx8qxp_ldb_ch->base;
> +     struct ldb_channel *companion_ldb_ch;
> +     struct device_node *companion;
> +     struct device_node *child;
> +     struct device_node *companion_port = NULL;
> +     struct device_node *port1, *port2;
> +     struct device *dev = imx8qxp_ldb->dev;
> +     const struct of_device_id *match;
> +     u32 i;
> +     int ch_cnt;
> +     int dual_link;
> +     int ret;
> +
> +     /* Locate the companion LDB for dual-link operation, if any. */
> +     companion = of_parse_phandle(dev->of_node, "fsl,companion-ldb", 0);
> +     if (!companion)
> +             return 0;
> +
> +     if (!of_device_is_available(companion)) {
> +             DRM_DEV_ERROR(dev, "companion LDB is not available\n");
> +             ret = -ENODEV;
> +             goto out;
> +     }
> +
> +     /*
> +      * Sanity check: the companion bridge must have the same compatible
> +      * string.
> +      */
> +     match = of_match_device(dev->driver->of_match_table, dev);
> +     if (!of_device_is_compatible(companion, match->compatible)) {
> +             DRM_DEV_ERROR(dev, "companion LDB is incompatible\n");
> +             ret = -ENXIO;
> +             goto out;
> +     }
> +
> +     ch_cnt = of_get_available_child_count(companion);
> +     if (ch_cnt == 0) {
> +             DRM_DEV_ERROR(dev, "no available companion LDB channel\n");
> +             ret = -ENODEV;
> +             goto out;
> +     } else if (ch_cnt > 1) {
> +             DRM_DEV_ERROR(dev, "invalid available companion LDB 
> channels\n");
> +             ret = -ENOTSUPP;
> +             goto out;
> +     }
> +
> +     for_each_available_child_of_node(companion, child) {
> +             ret = of_property_read_u32(child, "reg", &i);
> +             if (ret || i > MAX_LDB_CHAN_NUM - 1) {
> +                     DRM_DEV_ERROR(dev,
> +                                   "invalid channel node address: %u\n", i);
> +                     ret = -EINVAL;
> +                     of_node_put(child);
> +                     goto out;
> +             }
> +
> +             companion_port = child;
> +             of_node_put(child);
> +             break;
> +     }
> +
> +     if (companion_port == NULL) {
> +             DRM_DEV_ERROR(dev,
> +                           "failed to find companion LDB channel port\n");
> +             ret = -EINVAL;
> +             goto out;
> +     }
> +
> +     /*
> +      * Channel numbers have to be different, because channel0 transmits
> +      * odd pixels and channel1 transmits even pixels.
> +      */
> +     if (i == ldb_ch->chno) {
> +             DRM_DEV_ERROR(dev, "invalid companion LDB channel number\n");
> +             ret = -EINVAL;
> +             goto out;
> +     }
> +
> +     /*
> +      * We need to work out if the sink is expecting us to function in
> +      * dual-link mode.  We do this by looking at the DT port nodes we are
> +      * connected to.  If they are marked as expecting odd pixels and
> +      * even pixels than we need to enable LDB split mode.
> +      */
> +     port1 = of_graph_get_port_by_id(ldb_ch->np, 1);
> +     port2 = of_graph_get_port_by_id(companion_port, 1);
> +     dual_link = drm_of_lvds_get_dual_link_pixel_order(port1, port2);
> +     of_node_put(port1);
> +     of_node_put(port2);
> +
> +     switch (dual_link) {
> +     case DRM_LVDS_DUAL_LINK_ODD_EVEN_PIXELS:
> +             ldb_ch->link_type = LDB_CH_DUAL_LINK_ODD_EVEN_PIXELS;
> +             break;
> +     case DRM_LVDS_DUAL_LINK_EVEN_ODD_PIXELS:
> +             ldb_ch->link_type = LDB_CH_DUAL_LINK_EVEN_ODD_PIXELS;
> +             break;
> +     default:
> +             ret = dual_link;
> +             DRM_DEV_ERROR(dev,
> +                           "failed to get dual link pixel order: %d\n", ret);
> +             goto out;
> +     }
> +
> +     ret = imx8qxp_ldb_check_chno_and_dual_link(ldb_ch, dual_link);
> +     if (ret < 0) {
> +             DRM_DEV_ERROR(dev,
> +                           "unmatched channel number(%u) vs dual link(%d)\n",
> +                                                     ldb_ch->chno, 
> dual_link);
> +             goto out;
> +     }
> +
> +     imx8qxp_ldb->companion = of_drm_find_bridge(companion_port);
> +     if (!imx8qxp_ldb->companion) {
> +             ret = -EPROBE_DEFER;
> +             DRM_DEV_DEBUG_DRIVER(dev,
> +                    "failed to find bridge for companion bridge: %d\n", ret);
> +             goto out;
> +     }
> +
> +     DRM_DEV_DEBUG_DRIVER(dev,
> +             "dual-link configuration detected (companion bridge %pOF)\n",
> +                                                             companion);
> +
> +     companion_ldb_ch = bridge_to_ldb_ch(imx8qxp_ldb->companion);
> +     companion_ldb_ch->link_type = ldb_ch->link_type;
> +out:
> +     of_node_put(companion);
> +     return ret;
> +}
> +
> +static int imx8qxp_ldb_probe(struct platform_device *pdev)
> +{
> +     struct device *dev = &pdev->dev;
> +     struct imx8qxp_ldb *imx8qxp_ldb;
> +     struct imx8qxp_ldb_channel *imx8qxp_ldb_ch;
> +     struct ldb *ldb;
> +     struct ldb_channel *ldb_ch;
> +     int ret, i;
> +
> +     imx8qxp_ldb = devm_kzalloc(dev, sizeof(*imx8qxp_ldb), GFP_KERNEL);
> +     if (!imx8qxp_ldb)
> +             return -ENOMEM;
> +
> +     imx8qxp_ldb->clk_pixel = devm_clk_get(dev, "pixel");
> +     if (IS_ERR(imx8qxp_ldb->clk_pixel)) {
> +             ret = PTR_ERR(imx8qxp_ldb->clk_pixel);
> +             if (ret != -EPROBE_DEFER)
> +                     DRM_DEV_ERROR(dev,
> +                                   "failed to get pixel clock: %d\n", ret);
> +             return ret;
> +     }
> +
> +     imx8qxp_ldb->clk_bypass = devm_clk_get(dev, "bypass");
> +     if (IS_ERR(imx8qxp_ldb->clk_bypass)) {
> +             ret = PTR_ERR(imx8qxp_ldb->clk_bypass);
> +             if (ret != -EPROBE_DEFER)
> +                     DRM_DEV_ERROR(dev,
> +                                   "failed to get bypass clock: %d\n", ret);
> +             return ret;
> +     }
> +
> +     imx8qxp_ldb->dev = dev;
> +
> +     ldb = &imx8qxp_ldb->base;
> +     ldb->dev = dev;
> +     ldb->ctrl_reg = 0xe0;
> +
> +     for (i = 0; i < MAX_LDB_CHAN_NUM; i++)
> +             ldb->channel[i] = &imx8qxp_ldb->channel[i].base;
> +
> +     ret = ldb_init_helper(ldb);
> +     if (ret)
> +             return ret;
> +
> +     if (ldb->available_ch_cnt == 0) {
> +             DRM_DEV_DEBUG_DRIVER(dev, "no available channel\n");
> +             return 0;
> +     } else if (ldb->available_ch_cnt > 1) {
> +             DRM_DEV_ERROR(dev, "invalid available channel number(%u)\n",
> +                                                     ldb->available_ch_cnt);
> +             return -ENOTSUPP;
> +     }
> +
> +     for (i = 0; i < MAX_LDB_CHAN_NUM; i++) {
> +             imx8qxp_ldb_ch = &imx8qxp_ldb->channel[i];
> +             ldb_ch = &imx8qxp_ldb_ch->base;
> +
> +             if (ldb_ch->is_available) {
> +                     imx8qxp_ldb->active_chno = ldb_ch->chno;
> +                     break;
> +             }
> +     }
> +
> +     imx8qxp_ldb_ch->phy = devm_of_phy_get(dev, ldb_ch->np, "lvds_phy");
> +     if (IS_ERR(imx8qxp_ldb_ch->phy)) {
> +             ret = PTR_ERR(imx8qxp_ldb_ch->phy);
> +             if (ret != -EPROBE_DEFER)
> +                     DRM_DEV_ERROR(dev, "failed to get channel%d PHY: %d\n",
> +                                             imx8qxp_ldb->active_chno, ret);
> +             return ret;
> +     }
> +
> +     ret = ldb_find_next_bridge_helper(ldb);
> +     if (ret)
> +             return ret;
> +
> +     ret = imx8qxp_ldb_set_di_id(imx8qxp_ldb);
> +     if (ret)
> +             return ret;
> +
> +     ret = imx8qxp_ldb_parse_dt_companion(imx8qxp_ldb);
> +     if (ret)
> +             return ret;
> +
> +     platform_set_drvdata(pdev, imx8qxp_ldb);
> +     pm_runtime_enable(dev);
> +
> +     ldb_add_bridge_helper(ldb, &imx8qxp_ldb_bridge_funcs);
> +
> +     return ret;
> +}
> +
> +static int imx8qxp_ldb_remove(struct platform_device *pdev)
> +{
> +     struct imx8qxp_ldb *imx8qxp_ldb = platform_get_drvdata(pdev);
> +     struct ldb *ldb = &imx8qxp_ldb->base;
> +
> +     ldb_remove_bridge_helper(ldb);
> +
> +     pm_runtime_disable(&pdev->dev);
> +
> +     return 0;
> +}
> +
> +static int __maybe_unused imx8qxp_ldb_runtime_suspend(struct device *dev)
> +{
> +     return 0;
> +}
> +
> +static int __maybe_unused imx8qxp_ldb_runtime_resume(struct device *dev)
> +{
> +     struct imx8qxp_ldb *imx8qxp_ldb = dev_get_drvdata(dev);
> +     struct ldb *ldb = &imx8qxp_ldb->base;
> +
> +     /* disable LDB by resetting the control register to POR default */
> +     regmap_write(ldb->regmap, ldb->ctrl_reg, 0);
> +
> +     return 0;
> +}
> +
> +static const struct dev_pm_ops imx8qxp_ldb_pm_ops = {
> +     SET_RUNTIME_PM_OPS(imx8qxp_ldb_runtime_suspend,
> +                        imx8qxp_ldb_runtime_resume, NULL)
> +};
> +
> +static const struct of_device_id imx8qxp_ldb_dt_ids[] = {
> +     { .compatible = "fsl,imx8qxp-ldb" },
> +     { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, imx8qxp_ldb_dt_ids);
> +
> +static struct platform_driver imx8qxp_ldb_driver = {
> +     .probe  = imx8qxp_ldb_probe,
> +     .remove = imx8qxp_ldb_remove,
> +     .driver = {
> +             .pm = &imx8qxp_ldb_pm_ops,
> +             .name = DRIVER_NAME,
> +             .of_match_table = imx8qxp_ldb_dt_ids,
> +     },
> +};
> +module_platform_driver(imx8qxp_ldb_driver);
> +
> +MODULE_DESCRIPTION("i.MX8QXP LVDS Display Bridge(LDB) bridge driver");
> +MODULE_AUTHOR("Liu Ying <victor....@nxp.com>");
> +MODULE_LICENSE("GPL v2");
> +MODULE_ALIAS("platform:" DRIVER_NAME);

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