On 2018-02-27 11:44 AM, Michel Dänzer wrote: > On 2018-02-27 05:16 PM, Harry Wentland wrote: >> On 2018-02-27 11:08 AM, Michel Dänzer wrote: >>> On 2018-02-27 04:54 PM, Leo Li wrote: >>>> On 2018-02-27 05:34 AM, Michel Dänzer wrote: >>>>> On 2018-02-26 09:15 PM, Harry Wentland wrote: >>>>>> From: "Leo (Sunpeng) Li" <sunpeng.li at amd.com> >>>>>> >>>>>> Non-legacy LUT size should reflect hw capability. Change size from 256 >>>>>> to 4096. >>>>>> >>>>>> However, X doesn't seem to play with legacy LUTs of such size. >>>>>> Therefore, check for legacy lut when updating DC states, and update >>>>>> accordingly. >>>>>> >>>>>> v2: Use a macro for the maximum drm LUT value. >>>>>> >>>>>> Signed-off-by: Leo (Sunpeng) Li <sunpeng.li at amd.com> >>>>>> Reviewed-by: Harry Wentland <Harry.Wentland at amd.com> >>>>>> --- >>>>>>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 +- >>>>>>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h | 4 +- >>>>>>  .../drm/amd/display/amdgpu_dm/amdgpu_dm_color.c   | 77 >>>>>> ++++++++++++++++------ >>>>>>  3 files changed, 61 insertions(+), 22 deletions(-) >>>>>> >>>>>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c >>>>>> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c >>>>>> index bb9405daa087..f782518fc424 100644 >>>>>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c >>>>>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c >>>>>> @@ -3228,7 +3228,7 @@ static int amdgpu_dm_crtc_init(struct >>>>>> amdgpu_display_manager *dm, >>>>>>      dm->adev->mode_info.crtcs[crtc_index] = acrtc; >>>>>>      drm_crtc_enable_color_mgmt(&acrtc->base, MAX_COLOR_LUT_ENTRIES, >>>>>>                     true, MAX_COLOR_LUT_ENTRIES); >>>>>> -   drm_mode_crtc_set_gamma_size(&acrtc->base, MAX_COLOR_LUT_ENTRIES); >>>>>> +   drm_mode_crtc_set_gamma_size(&acrtc->base, >>>>>> MAX_COLOR_LEGACY_LUT_ENTRIES); >>>>> >>>>> This means userspace can't set gamma ramps with more than 256 entries, >>>>> since drm_mode_gamma_set_ioctl returns an error if the sizes don't >>>>> match. We should just fix userspace which tries to use the wrong size. >>>> >>>> It seems X hard-codes 256 entries for the legacy lut, ignoring what the >>>> kernel requests: >>>> >>>> xf86CrtcCreate in xserver/hw/xfree86/modes/xf86Crtc.c (~line 120): >>>> >>>> /* Preallocate gamma at a sensible size. */ >>>> crtc->gamma_size = 256; >>>> >>>> >>>> I confirmed this as well via a printk on the user LUT size in >>>> drm_mode_gamma_set_ioctl (after reverting to 4096 gamma size, of course). >>>> >>>> I'm not sure if modifying that line in X will be straightforward. >>> >>> It could be overridden by the DDX driver. However, there is the issue of >>> using an older DDX driver with a newer kernel. >>> >>> >>>> It's worth noting that drm_mode_crtc_set_gamma_size() only sets the legacy >>>> gamma size. Non-legacy gamma (de/regamma) sizes are reported via a mode >>>> property, and does not conflict with legacy size. Therefore, reporting a >>>> different size for legacy shouldn't be an issue, AFAIK; as long as we >>>> check the DRM lut size and update DC accordingly, which we're doing. >>> >>> Makes sense, but it means that gamma will not work for 30-bit colour in >>> Xorg until the DDX driver uses the new gamma mechanism, which might >>> require switching to the atomic KMS API as well. Is that okay? >>> >> >> That's still current behavior, so this patch is not changing anything there. We could increase it but how would we deal with old DDX/X that assumes 256? Would it make sense instead to teach X to set the new gamma_lut property? > > Maybe. Can it be used without using the atomic KMS UAPI in general? > Both legacy and atomic KMS can set non-legacy gamma(the new degamma_lut, ctm, and gamma_lut properties on CRTC). Legacy KMS can use DRM_IOCTL_MODE_SETPROPERTY to set these. IGT exercises both atomic and non-atomic KMS code paths to test these properties. Only legacy KMS sets the legacy gamma property through the DRM_IOCTL_MODE_SETGAMMA IOCTL. Harry >
