Hi Jani
On 2020-04-06 01:32, Jani Nikula wrote:
On Fri, 03 Apr 2020, abhinavk@xxxxxxxxxxxxxx wrote:
On 2020-04-03 13:39, Ville Syrjala wrote:
diff --git a/drivers/gpu/drm/drm_modes.c
b/drivers/gpu/drm/drm_modes.c
index fec1c33b3045..e3d5f011f7bd 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -759,9 +759,7 @@ int drm_mode_vrefresh(const struct
drm_display_mode
*mode)
{
int refresh = 0;
- if (mode->vrefresh > 0)
- refresh = mode->vrefresh;
The mode->vrefresh has been replaced with calling this API in all its
usages.
However in this API, the above if statement was returning the vrefresh
if it was already
set. mode->clock is holding the pixel clock . So this will not cause
any
issues in non-compressed cases.
In case of compression like DSC, the pixel
clock will be different based on the compression ratio hence the
mode->clock will change but fps will not.
So we did have usages in our downstream driver where we would use this
API and the refresh rate
returned will be the mode->vrefresh which did not change but after
this
change for those cases it will end up returning the refresh rate
calculated using mode->clock which will result in a different value
now.
So is the recommendation that even in the case of compression
mode->clock should always hold
uncompressed pixel clock value because with this part of the change we
will now get a different value when we call this API.
Yes. The mode remains the same regardless of compression, and
compression is just an implementation detail of the transport.
You may need to maintain separate "physical port clock" and "logical
port clock" for DSC, where the latter is a function of the former and
the DSC parameters. And then you can see if your logical port clock
provides enough bandwidth for your mode. But this is up to your driver
and encoder implementation.
BR,
Jani.
Thanks for the information. We will make changes to our driver to
accommodate the changes in the
drm_mode_vrefresh API.
Thanks
Abhinav
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