On 4/18/2023 6:16 PM, Ville Syrjälä wrote:
On Mon, Apr 17, 2023 at 03:48:12PM -0700, Manasi Navare wrote:
Hi Ville,
Could you suggest how to handle the intel_dp_link_compute_config()
when the max_bpp is returned as 0, currently
it just exits the loop and returns a -EINVAL and this triggers the DSC path.
While we should be completely failing the modeset and encoder_config
in this case instead of trying DSC, correct?
The DSC path needs to handle the bpp limits correctly:
1. Take the baseline limits already computed
2. Further restrict them based on sink/source DSC capabilities/etc.
3. Make sure the uncompressed bpp value chosen is between the min/max
I have some older patch to try similar thing [1]. We try to iterate over
bpc to find pipe_bpp in the limits, then try to find out compressed_bpp.
But if intel_dp_max_bpp returns 0, limits.max_bpp is set to 0, so we
discard this for dsc case and re-calculate the limits.max_bpp?
[1] https://patchwork.freedesktop.org/patch/519346/?series=111391&rev=3
Manasi
On Thu, Apr 13, 2023 at 8:23 AM Manasi Navare <navaremanasi@xxxxxxxxxxxx> wrote:
On Tue, Apr 11, 2023 at 10:22 PM Ville Syrjälä
<ville.syrjala@xxxxxxxxxxxxxxx> wrote:
On Tue, Apr 11, 2023 at 05:07:01PM -0700, Manasi Navare wrote:
On Tue, Apr 11, 2023 at 10:42 AM Ville Syrjälä
<ville.syrjala@xxxxxxxxxxxxxxx> wrote:
On Tue, Apr 11, 2023 at 05:34:08PM +0000, Manasi Navare wrote:
In the function intel_dp_max_bpp(), currently if bpc < 0 in case of error,
we return 0 instead of returning an err code of -EINVAL.
This throws off the logic in the calling function.
What logic? The caller doesn't expect to get an error.
If this returns a 0, we end up using limits.max_bpp = 0 and in
intel_dp_compute_link_config_wide(),
since max_bpp is 0, it exits this for loop:
for (bpp = limits->max_bpp; bpp >= limits->min_bpp; bpp -= 2 * 3) and returns
-EINVAL which then wrongly goes to enable DSC even when link BW is
sufficient without DSC.
And how woud max_bpp<0 prevent that?
The real problem seems to be that the DSC code totally
ignores bpp limits.
Hi Ville,
So I see a few concerns/questions:
- Why is the Max bpp value 0 in intel_dp_max_bpp, is that a valid case
and how should our link configurations handle that case when max_bpp
is 0?
- This is happening in a bug I am looking at with HDMI PCON, @Ankit
Nautiyal have we ever seen something similar where max_bpp for HDMi
PCON
is returned 0?
- I dont think its a problem with DSC code, but rather
intel_dp_compute_link_config() outer for loop where we vary
from max_bpp to min_bpp and see if any bpp works with available link
bw, how should we handle this when max_bpp = 0 if you are saying thats
a valid case?
- In this patch if I return -EINVAL instead of 0, then atleast the
entire encoder_config will fail and that will fail the modeset, since
it assumes max_bpp cannot be 0
Could you please help answer above concerns and how to handle max bpp
= 0 case if that is valid? This patch is simply making that invalid
resulting into modeset failure
Manasi
--
Ville Syrjälä
Intel
