On rockchip rk3288, only word(32-bit) accesses are
permitted for hdmi registers.  Byte width accesses (writeb,
readb) generate an imprecise external abort.

Signed-off-by: Andy Yan <andy....@rock-chips.com>

---

Changes in v10: None
Changes in v9: None
Changes in v8: None
Changes in v7: None
Changes in v6:
- move some modification to  patch#6
- refactor register access without reg_shift

Changes in v5:
- refactor reg-io-width

Changes in v4: None
Changes in v3:
- split multi register access to one indepent patch

Changes in v2: None

 drivers/gpu/drm/bridge/dw_hdmi.c | 57 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 51 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c b/drivers/gpu/drm/bridge/dw_hdmi.c
index 4f9a5c0..d7bf46d 100644
--- a/drivers/gpu/drm/bridge/dw_hdmi.c
+++ b/drivers/gpu/drm/bridge/dw_hdmi.c
@@ -101,6 +101,11 @@ struct hdmi_data_info {
        struct hdmi_vmode video_mode;
 };
 
+union dw_reg_ptr {
+       u32 __iomem *p32;
+       u8 __iomem *p8;
+};
+
 struct dw_hdmi {
        struct drm_connector connector;
        struct drm_encoder encoder;
@@ -121,20 +126,43 @@ struct dw_hdmi {
 
        struct regmap *regmap;
        struct i2c_adapter *ddc;
-       void __iomem *regs;
+       union dw_reg_ptr regs;
 
        unsigned int sample_rate;
        int ratio;
+
+       void (*write)(struct dw_hdmi *hdmi, u8 val, int offset);
+       u8 (*read)(struct dw_hdmi *hdmi, int offset);
 };
 
+static void dw_hdmi_writel(struct dw_hdmi *hdmi, u8 val, int offset)
+{
+       writel(val, hdmi->regs.p32 + offset);
+}
+
+static u8 dw_hdmi_readl(struct dw_hdmi *hdmi, int offset)
+{
+       return readl(hdmi->regs.p32 + offset);
+}
+
+static void dw_hdmi_writeb(struct dw_hdmi *hdmi, u8 val, int offset)
+{
+       writeb(val, hdmi->regs.p8 + offset);
+}
+
+static u8 dw_hdmi_readb(struct dw_hdmi *hdmi, int offset)
+{
+       return readb(hdmi->regs.p8 + offset);
+}
+
 static inline void hdmi_writeb(struct dw_hdmi *hdmi, u8 val, int offset)
 {
-       writeb(val, hdmi->regs + offset);
+       hdmi->write(hdmi, val, offset);
 }
 
 static inline u8 hdmi_readb(struct dw_hdmi *hdmi, int offset)
 {
-       return readb(hdmi->regs + offset);
+       return hdmi->read(hdmi, offset);
 }
 
 static void hdmi_modb(struct dw_hdmi *hdmi, u8 data, u8 mask, unsigned reg)
@@ -1528,6 +1556,23 @@ static int dw_hdmi_bind(struct device *dev, struct 
device *master, void *data)
        struct device_node *ddc_node;
        struct resource *iores;
        int ret, irq;
+       u32 val = 1;
+
+       of_property_read_u32(np, "reg-io-width", &val);
+
+       switch (val) {
+       case 4:
+               hdmi->write = dw_hdmi_writel;
+               hdmi->read = dw_hdmi_readl;
+               break;
+       case 1:
+               hdmi->write = dw_hdmi_writeb;
+               hdmi->read = dw_hdmi_readb;
+               break;
+       default:
+               dev_err(dev, "reg-io-width must be 1 or 4\n");
+               return -EINVAL;
+       }
 
        ddc_node = of_parse_phandle(np, "ddc-i2c-bus", 0);
        if (ddc_node) {
@@ -1554,9 +1599,9 @@ static int dw_hdmi_bind(struct device *dev, struct device 
*master, void *data)
                return ret;
 
        iores = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-       hdmi->regs = devm_ioremap_resource(dev, iores);
-       if (IS_ERR(hdmi->regs))
-               return PTR_ERR(hdmi->regs);
+       hdmi->regs.p32 = devm_ioremap_resource(dev, iores);
+       if (IS_ERR(hdmi->regs.p32))
+               return PTR_ERR(hdmi->regs.p32);
 
        if (hdmi->plat_data->setup)
                hdmi->priv = hdmi->plat_data->setup(pdev);
-- 
1.9.1

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