[PATCH 13/22] drm/i915: CHV: Pipe level Gamma correction

[Emil Velikov]

Hi Shashank,

On 9 October 2015 at 20:29, Shashank Sharma <shashank.sharma at intel.com> wrote:
> CHV/BSW platform supports two different pipe level gamma
> correction modes, which are:
> 1. Legacy 8-bit mode
> 2. 10-bit CGM (Color Gamut Mapping) mode
>
> This patch does the following:
> 1. Attaches Gamma property to CRTC
> 3. Adds the core Gamma correction function for CHV/BSW
> 4. Adds Gamma correction macros
>
> Signed-off-by: Shashank Sharma <shashank.sharma at intel.com>
> Signed-off-by: Kausal Malladi <kausalmalladi at gmail.com>
> ---
>  drivers/gpu/drm/i915/i915_reg.h            |  12 +++
>  drivers/gpu/drm/i915/intel_color_manager.c | 114 +++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_color_manager.h |  13 ++++
>  3 files changed, 139 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 60e6a73..885ac8a 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -8038,4 +8038,16 @@ enum skl_disp_power_wells {
>  #define GEN9_VEBOX_MOCS_0      0xcb00  /* Video MOCS base register*/
>  #define GEN9_BLT_MOCS_0                0xcc00  /* Blitter MOCS base register*/
>
> +/* Color Management */
> +#define PIPEA_CGM_CONTROL                      (VLV_DISPLAY_BASE + 0x67A00)
> +#define PIPEB_CGM_CONTROL                      (VLV_DISPLAY_BASE + 0x69A00)
> +#define PIPEC_CGM_CONTROL                      (VLV_DISPLAY_BASE + 0x6BA00)
> +#define PIPEA_CGM_GAMMA                        (VLV_DISPLAY_BASE + 0x67000)
> +#define PIPEB_CGM_GAMMA                        (VLV_DISPLAY_BASE + 0x69000)
> +#define PIPEC_CGM_GAMMA                        (VLV_DISPLAY_BASE + 0x6B000)
> +#define _PIPE_CGM_CONTROL(pipe) \
> +       (_PIPE3(pipe, PIPEA_CGM_CONTROL, PIPEB_CGM_CONTROL, PIPEC_CGM_CONTROL))
> +#define _PIPE_GAMMA_BASE(pipe) \
> +       (_PIPE3(pipe, PIPEA_CGM_GAMMA, PIPEB_CGM_GAMMA, PIPEC_CGM_GAMMA))
> +
>  #endif /* _I915_REG_H_ */
> diff --git a/drivers/gpu/drm/i915/intel_color_manager.c b/drivers/gpu/drm/i915/intel_color_manager.c
> index e466748..cf381b8 100644
> --- a/drivers/gpu/drm/i915/intel_color_manager.c
> +++ b/drivers/gpu/drm/i915/intel_color_manager.c
> @@ -27,6 +27,112 @@
>
>  #include "intel_color_manager.h"
>
> +static int chv_set_gamma(struct drm_device *dev, struct drm_property_blob *blob,
> +               struct drm_crtc *crtc)
> +{
> +       bool flag = false;
> +       enum pipe pipe;
> +       u16 red_fract, green_fract, blue_fract;
> +       u32 red, green, blue, num_samples;
> +       u32 word = 0;
> +       u32 count = 0;
> +       u32 cgm_gamma_reg = 0;
> +       u32 cgm_control_reg = 0;
> +       int ret = 0, length;
> +       struct drm_r32g32b32 *correction_values = NULL;
You can drop the useless initialization of correction_values. Same
goes for patches 19 and 21.

> +       struct drm_palette *gamma_data;
> +       struct drm_i915_private *dev_priv = dev->dev_private;
> +
> +       if (WARN_ON(!blob))
> +               return -EINVAL;
> +
> +       gamma_data = (struct drm_palette *)blob->data;
> +       pipe = to_intel_crtc(crtc)->pipe;
> +       num_samples = gamma_data->num_samples;
> +       length = num_samples * sizeof(struct drm_r32g32b32);
Calculation can overflow.

> +
> +       switch (num_samples) {
> +       case GAMMA_DISABLE_VALS:
> +
> +               /* Disable Gamma functionality on Pipe - CGM Block */
> +               cgm_control_reg = I915_READ(_PIPE_CGM_CONTROL(pipe));
> +               cgm_control_reg &= ~CGM_GAMMA_EN;
> +               I915_WRITE(_PIPE_CGM_CONTROL(pipe), cgm_control_reg);
> +
> +               DRM_DEBUG_DRIVER("Gamma disabled on Pipe %c\n",
> +               pipe_name(pipe));
Indentation looks wrong here.

> +               ret = 0;
Drop the variable and return 0, at the bottom of the function ?

> +               break;
> +
> +       case CHV_8BIT_GAMMA_MAX_VALS:
> +       case CHV_10BIT_GAMMA_MAX_VALS:
> +
> +               count = 0;
> +               cgm_gamma_reg = _PIPE_GAMMA_BASE(pipe);
> +               correction_values = (struct drm_r32g32b32 *)&gamma_data->lut;
> +
> +               while (count < num_samples) {
Using for(i = 0;....) loop seems the more common approach ?

[snip]
> +                       /*
> +                       * On CHV, the best supported Gamma capability is
> +                       * CGM block, that takes 257 samples.
> +                       * If user gives 256 samples (legacy mode), then
> +                       * duplicate the 256th value to 257th.
> +                       * "flag" is used to make sure it happens only once
> +                       */
> +                       if (num_samples == CHV_8BIT_GAMMA_MAX_VALS &&
> +                               count == CHV_8BIT_GAMMA_MAX_VALS && !flag) {
> +                               count--;
> +                               flag = true;
> +                       }
There is little point in going over this if statement 256 odd times.
Split it out of the loop ?

> +               }
> +
> +               /* Enable (CGM) Gamma on Pipe */
> +               I915_WRITE(_PIPE_CGM_CONTROL(pipe),
> +               I915_READ(_PIPE_CGM_CONTROL(pipe)) | CGM_GAMMA_EN);
> +               DRM_DEBUG_DRIVER("CGM Gamma enabled on Pipe %c\n",
> +               pipe_name(pipe));
Indentation.

> +               ret = 0;
Drop the variable ?

> +               break;
> +
> +       default:
> +               DRM_ERROR("Invalid number of samples for Gamma LUT\n");
> +               ret = -EINVAL;
return -EINVAL;

> +       }
> +
> +       return ret;
return 0;


Regards,
Emil