| Message ID | 20230629122534.8815-1-stanislav.lisovskiy@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/i915: Fail if DSC compression requirement is less than platform supports | expand |
On Thu, 2023-06-29 at 15:25 +0300, Stanislav Lisovskiy wrote: > Currently we just clamp that value to the highest supported one, however that > means, we are not able to fit this into our available bandwidth range, so we > might see glitches or FIFO underruns. > While choosing less compressed bpp than min bpp required to handle the mode is > harmless and might even save some bandwidth, choosing higher compressed bpp than > min bpp required to handle the required mode config, can cause issues. > So in that case lets just conclude that even with DSC, we are not able to comply > with bandwidth requirements and fail. > > v2: - s/clamp_t/min_t/ (Luca Coelho) > > Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com> > --- > drivers/gpu/drm/i915/display/intel_dp.c | 13 +++++++++++-- > 1 file changed, 11 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c > index 9f40da20e88d..03675620e3ea 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp.c > +++ b/drivers/gpu/drm/i915/display/intel_dp.c > @@ -713,9 +713,18 @@ u32 intel_dp_dsc_nearest_valid_bpp(struct drm_i915_private *i915, u32 bpp, u32 p > > /* > * According to BSpec, 27 is the max DSC output bpp, > - * 8 is the min DSC output bpp > + * 8 is the min DSC output bpp. > + * While we can still clamp higher bpp values to 27, saving bandwidth, > + * if it is required to oompress up to bpp < 8, means we can't do > + * that and probably means we can't fit the required mode, even with > + * DSC enabled. > */ > - bits_per_pixel = clamp_t(u32, bits_per_pixel, 8, 27); > + if (bits_per_pixel < 8) { > + drm_dbg_kms(&i915->drm, "Unsupported BPP %u, min 8\n", > + bits_per_pixel); > + return 0; > + } > + bits_per_pixel = min_t(u32, bits_per_pixel, 27); > } else { > /* Find the nearest match in the array of known BPPs from VESA */ > for (i = 0; i < ARRAY_SIZE(valid_dsc_bpp) - 1; i++) { Reviewed-by: Luca Coelho <luciano.coelho@intel.com> -- Cheers, Luca.
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c index 9f40da20e88d..03675620e3ea 100644 --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -713,9 +713,18 @@ u32 intel_dp_dsc_nearest_valid_bpp(struct drm_i915_private *i915, u32 bpp, u32 p /* * According to BSpec, 27 is the max DSC output bpp, - * 8 is the min DSC output bpp + * 8 is the min DSC output bpp. + * While we can still clamp higher bpp values to 27, saving bandwidth, + * if it is required to oompress up to bpp < 8, means we can't do + * that and probably means we can't fit the required mode, even with + * DSC enabled. */ - bits_per_pixel = clamp_t(u32, bits_per_pixel, 8, 27); + if (bits_per_pixel < 8) { + drm_dbg_kms(&i915->drm, "Unsupported BPP %u, min 8\n", + bits_per_pixel); + return 0; + } + bits_per_pixel = min_t(u32, bits_per_pixel, 27); } else { /* Find the nearest match in the array of known BPPs from VESA */ for (i = 0; i < ARRAY_SIZE(valid_dsc_bpp) - 1; i++) {
Currently we just clamp that value to the highest supported one, however that means, we are not able to fit this into our available bandwidth range, so we might see glitches or FIFO underruns. While choosing less compressed bpp than min bpp required to handle the mode is harmless and might even save some bandwidth, choosing higher compressed bpp than min bpp required to handle the required mode config, can cause issues. So in that case lets just conclude that even with DSC, we are not able to comply with bandwidth requirements and fail. v2: - s/clamp_t/min_t/ (Luca Coelho) Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com> --- drivers/gpu/drm/i915/display/intel_dp.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)