Hi Annie, This might add a day or two, but considering this is a long weekend in India, you can expect the patches by mid next week.
Regards Shashank -----Original Message----- From: Matheson, Annie J Sent: Wednesday, September 30, 2015 10:01 PM To: Sharma, Shashank Cc: Bradford, Robert; Roper, Matthew D; Bish, Jim; Smith, Gary K; dri-devel@lists.freedesktop.org; intel-gfx@lists.freedesktop.org; Vetter, Daniel; Mukherjee, Indranil; Palleti, Avinash Reddy; kausalmalladi@gmail.com Subject: Re: [PATCH 21/23] drm/i915: BDW: Pipe level Gamma correction
Shashank,
Please let us know when the next patch series would be ready assuming you incorporate the feedback from Rob.
I would like to hope we're done with feedback at this point.
Thanks.
Annie Matheson
On Sep 30, 2015, at 9:25 AM, Sharma, Shashank shashank.sharma@intel.com wrote:
Hey Rob,
Thanks for the feedback, and the testing efforts. I will check into your suggestions and get back.
Regards Shashank -----Original Message----- From: Bradford, Robert Sent: Wednesday, September 30, 2015 8:02 PM To: Sharma, Shashank; Roper, Matthew D; Bish, Jim; Smith, Gary K; dri-devel@lists.freedesktop.org; intel-gfx@lists.freedesktop.org Cc: Vetter, Daniel; Matheson, Annie J; Mukherjee, Indranil; Palleti, Avinash Reddy; kausalmalladi@gmail.com Subject: Re: [PATCH 21/23] drm/i915: BDW: Pipe level Gamma correction
Hi Shashank, some feedback below that you would be great to get addressed before your next version.
On Wed, 2015-09-16 at 23:07 +0530, Shashank Sharma wrote: BDW/SKL/BXT platforms support various Gamma correction modes which are:
- Legacy 8-bit mode
- 10-bit mode
- 10-bit Split Gamma mode
- 12-bit mode
This patch does the following:
- Adds the core function to program Gamma correction values
for BDW/SKL/BXT platforms 2. Adds Gamma correction macros/defines
Signed-off-by: Shashank Sharma shashank.sharma@intel.com Signed-off-by: Kausal Malladi kausalmalladi@gmail.com
drivers/gpu/drm/i915/i915_reg.h | 17 +- drivers/gpu/drm/i915/intel_color_manager.c | 270 +++++++++++++++++++++++++++++
*snip*
+static u32 bdw_write_10bit_gamma_precision(u32 red, u32 green, u32 blue) +{
- u32 word;
- u8 blue_int, green_int, red_int;
- u16 blue_fract, green_fract, red_fract;
- blue_int = _GAMMA_INT_PART(blue);
- if (blue_int > GAMMA_INT_MAX)
blue = BDW_MAX_GAMMA;- green_int = _GAMMA_INT_PART(green);
- if (green_int > GAMMA_INT_MAX)
green = BDW_MAX_GAMMA;- red_int = _GAMMA_INT_PART(red);
- if (red_int > GAMMA_INT_MAX)
red = BDW_MAX_GAMMA;- blue_fract = _GAMMA_FRACT_PART(blue);
- green_fract = _GAMMA_FRACT_PART(green);
- red_fract = _GAMMA_FRACT_PART(red);
- blue_fract >>= BDW_10BIT_GAMMA_MSB_SHIFT;
- green_fract >>= BDW_10BIT_GAMMA_MSB_SHIFT;
- red_fract >>= BDW_10BIT_GAMMA_MSB_SHIFT;
- /* Red (29:20) Green (19:10) and Blue (9:0) */
- word = red_fract;
- word <<= BDW_GAMMA_SHIFT;
- word = word | green_fract;
- word <<= BDW_GAMMA_SHIFT;
- word = word | blue_fract;
- return word;
+}
I think the above function, and perhaps others in this series have the same flaw with respect to maximum colour value.
In our discussions we agreed that we would follow the "GL style" where maximum colour (i.e. 255 in 8-bit) would be represented by 1.0f. 1.0f when converted to fixed point 8.24 notation is 1 << 24.
I observed that with my test code that a linear ramp (where the last entry is set to 1.0) gives me black for white. I tracked it down to this function.
In order to map 1.0 to the maximum value for the table entry in the hardware this function needs to be changed. One way to achieve this would be change the test "blue_int > GAMMA_INT_MAX" to be "blue_int >= GAMMA_INT_MAX" but since GAMMA_INT_MAX = 1 then it might be clearer to say blue_int > 0.
BDW_MAX_GAMMA also looks wrong. I think it should be (1 << 24) - 1 not the 0x10000 (see below). As well as correct clamping it is also necessary to scale as Daniel suggested on IRC:
" 13:54 < danvet> robster, so we'd need to rescale in the kernel from 1.0 to 0.1111111111b ? 13:55 < danvet> well substract 0.0000000001b for all values > 0.5 probably since float math in the kernel is evil 13:56 < danvet> also this probably needs an igt - check that all black with an all 1.0 gamma table is the same as all white with a linear one "
You won't see this with your test program (color-correction.c) as the largest value you program in appears to be 0.ff
*snip*
+/* Gen 9 */ +#define BDW_MAX_GAMMA 0x10000
*snip*
I look forward to testing against your next version.
Rob