On Wed, May 3, 2017 at 2:11 AM, Jani Nikula <jani.nik...@linux.intel.com>
wrote:
> On Tue, 18 Apr 2017, Puthikorn Voravootivat <put...@chromium.org> wrote:
> > Currently the intel_dp_aux_backlight driver requires eDP panel
> > to not also support backlight adjustment via PWM pin to use
> > this driver.
> >
> > This force the eDP panel that support both ways of backlight
> > adjustment to do it via PWM pin.
>
> Currently this is by design. But I think we agreed previously that the
> driver also has incorrect capability checks for the current design. The
> first priority would be to fix those checks. And the patch order in the
> series should reflect that.
>
> > This patch adds the new prefer DPCD mode in the i915_param
> > to make it enable to prefer DPCD over the PWM via kernel param.
> >
> > This patch also add a check to DP_EDP_BACKLIGHT_AUX_ENABLE_CAP
> > in set_aux_backlight_enable() since the backlight enablement
> > can be done via BL_ENABLE eDP connector pin in the case that
> > it does not support doing that via AUX.
>
> "also" in the commit message is a strong clue it should be a separate
> patch. What you describe is potentially a fix that should precede this
> patch.
>
I will split this into 3 patches.
1. Fix cap check
2. Drop AUX backlight enable requirement
3. Allow choosing to use PWM pin or AUX if both supported
> >
> > Signed-off-by: Puthikorn Voravootivat <put...@chromium.org>
> > ---
> > drivers/gpu/drm/i915/i915_params.c | 6 ++---
> > drivers/gpu/drm/i915/i915_params.h | 2 +-
> > drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 33
> +++++++++++++++++++--------
> > 3 files changed, 27 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_params.c
> b/drivers/gpu/drm/i915/i915_params.c
> > index b6a7e363d076..960393dd5edf 100644
> > --- a/drivers/gpu/drm/i915/i915_params.c
> > +++ b/drivers/gpu/drm/i915/i915_params.c
> > @@ -63,7 +63,7 @@ struct i915_params i915 __read_mostly = {
> > .huc_firmware_path = NULL,
> > .enable_dp_mst = true,
> > .inject_load_failure = 0,
> > - .enable_dpcd_backlight = false,
> > + .enable_dpcd_backlight = 0,
> > .enable_gvt = false,
> > };
> >
> > @@ -246,9 +246,9 @@ MODULE_PARM_DESC(enable_dp_mst,
> > module_param_named_unsafe(inject_load_failure,
> i915.inject_load_failure, uint, 0400);
> > MODULE_PARM_DESC(inject_load_failure,
> > "Force an error after a number of failure check points (0:disabled
> (default), N:force failure at the Nth failure check point)");
> > -module_param_named(enable_dpcd_backlight, i915.enable_dpcd_backlight,
> bool, 0600);
> > +module_param_named(enable_dpcd_backlight, i915.enable_dpcd_backlight,
> int, 0600);
> > MODULE_PARM_DESC(enable_dpcd_backlight,
> > - "Enable support for DPCD backlight control (default:false)");
> > + "Enable support for DPCD backlight control (0:disable (default),
> 1:prefer PWM pin, 2: prefer DPCD)");
>
> See my comments below. I think you need to rethink the options.
>
> >
> > module_param_named(enable_gvt, i915.enable_gvt, bool, 0400);
> > MODULE_PARM_DESC(enable_gvt,
> > diff --git a/drivers/gpu/drm/i915/i915_params.h
> b/drivers/gpu/drm/i915/i915_params.h
> > index 34148cc8637c..bf6e2c60f697 100644
> > --- a/drivers/gpu/drm/i915/i915_params.h
> > +++ b/drivers/gpu/drm/i915/i915_params.h
> > @@ -51,6 +51,7 @@
> > func(int, use_mmio_flip); \
> > func(int, mmio_debug); \
> > func(int, edp_vswing); \
> > + func(int, enable_dpcd_backlight); \
> > func(unsigned int, inject_load_failure); \
> > /* leave bools at the end to not create holes */ \
> > func(bool, alpha_support); \
> > @@ -66,7 +67,6 @@
> > func(bool, verbose_state_checks); \
> > func(bool, nuclear_pageflip); \
> > func(bool, enable_dp_mst); \
> > - func(bool, enable_dpcd_backlight); \
> > func(bool, enable_gvt)
> >
> > #define MEMBER(T, member) T member
> > diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > index 6532e226db29..42f73d9a3ccf 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > @@ -28,6 +28,10 @@ static void set_aux_backlight_enable(struct intel_dp
> *intel_dp, bool enable)
> > {
> > uint8_t reg_val = 0;
> >
> > + /* Early return when display use other mechanism to enable
> backlight. */
> > + if (!(intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP))
> > + return;
> > +
> > if (drm_dp_dpcd_readb(&intel_dp->aux, DP_EDP_DISPLAY_CONTROL_
> REGISTER,
> > ®_val) < 0) {
> > DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n",
> > @@ -138,27 +142,36 @@ static bool
> > intel_dp_aux_display_control_capable(struct intel_connector *connector)
> > {
> > struct intel_dp *intel_dp = enc_to_intel_dp(&connector->
> encoder->base);
> > + bool supported;
> >
> > /* Check the eDP Display control capabilities registers to
> determine if
> > * the panel can support backlight control over the aux channel
> > */
> > - if (intel_dp->edp_dpcd[1] & DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAP
> &&
> > - (intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP) &&
> > - !((intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_PIN_ENABLE_CAP) ||
> > - (intel_dp->edp_dpcd[2] &
> > DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP)))
> {
> > - DRM_DEBUG_KMS("AUX Backlight Control Supported!\n");
> > - return true;
> > + switch (i915.enable_dpcd_backlight) {
> > + case 1: /* prefer PWM pin */
> > + supported = (intel_dp->edp_dpcd[1] &
> > DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAP)
> &&
> > + (intel_dp->edp_dpcd[1] &
> DP_EDP_BACKLIGHT_AUX_ENABLE_CAP) &&
> > + !(intel_dp->edp_dpcd[1] &
> DP_EDP_BACKLIGHT_PIN_ENABLE_CAP) &&
> > + !(intel_dp->edp_dpcd[2] &
> DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP);
> > + break;
>
> This is not right. If we're going to use the PWM pin for backlight
> control, it's what's in intel_panel.c, and
> intel_dp_aux_init_backlight_funcs() should return -ENODEV. We only
> support one or the other.
>
Fixed in next patch set.
>
> I think you probably need to have a hard look at Table 10-1 "Summary of
> Backlight Control Modes Using DPCD Registers" in eDP 1.4b, and tell us
> what modes you really want to support and how. For example, the product
> mode or any DPCD/PWM mixed modes aren't very easily achieved with the
> current design.
>
What we actually need is that we have panel that
- does not support display backlight enable via AUX
- support display backlight adjustment via AUX
- support display backlight enable via eDP BL_ENABLE pin
- support display backlight adjustment via eDP PWM pin but that pin is not
connected
- support display backlight frequency adjustment via AUX
and we want to
- enable backlight via eDP BL_ENABLE pin
- adjust backlight brightness via AUX
- adjust backlight frequency via AUX
>
> BR,
> Jani.
>
>
> > + case 2: /* prefer DPCD */
> > + supported = (intel_dp->edp_dpcd[1] &
> > DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAP)
> &&
> > + (intel_dp->edp_dpcd[2] &
> DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP);
> > + break;
> > + default:
> > + supported = false;
> > }
> > - return false;
> > +
> > + if (supported)
> > + DRM_DEBUG_KMS("AUX Backlight Control Supported!\n");
> > +
> > + return supported;
> > }
> >
> > int intel_dp_aux_init_backlight_funcs(struct intel_connector
> *intel_connector)
> > {
> > struct intel_panel *panel = &intel_connector->panel;
> >
> > - if (!i915.enable_dpcd_backlight)
> > - return -ENODEV;
> > -
> > if (!intel_dp_aux_display_control_capable(intel_connector))
> > return -ENODEV;
>
> --
> Jani Nikula, Intel Open Source Technology Center
>
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