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? Harry >
