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? -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer
