On 18/07/2023 23:44, Jessica Zhang wrote:
On 7/17/2023 11:04 PM, Dmitry Baryshkov wrote:
On 18/07/2023 03:30, Jessica Zhang wrote:
In addition, *_is_widebus_enabled() would only work under the
assumption that DSC (if supported) will always be enabled during
bootup for DSI. If there ends up being support for a panel that
allows for DSC to be enabled on the fly after bootup, the proposed
*_is_widebus_enabled() check would break since the assumption that
DSC is always enabled on bootup would not be true anymore.
Why is that going to break?
Currently, the msm_host->dsc is initialized in attach() [1] and we do
widebus setup during power_on() [2]. So we can assume that if the panel
supports DSC, msm_host->dsc will be not NULL during power_on() and the
widebus setup will work as expected.
However, if a panel supports enabling DSC after bootup, then
msm_host->dsc will be set later within the commit enable() path meaning
the necessary widebus setup during power_on() would *not* happen (as
*_is_widebus_enabled() would return false on account of msm_host->dsc ==
NULL during power_on()).
Minor corrections:
- power_on() happens during pre_enable() stage,
- the dynamic msm_host->dsc can also be set during pre_enable() stage.
Note: there still exists dsi_mgr_bridge_mode_set(), which can also be
used to set msm_host->dsc (however I would prefer to drop mode_set()
completely and set the mode from atomic_enable().
I'd say, this is the minor issue. The dsi_timing_setup() is plagued with
if (dsc) checks, so if we make DSC dynamic, it will have to be audited
anyway.
Thanks,
Jessica Zhang
[1]
https://elixir.bootlin.com/linux/v6.5-rc2/source/drivers/gpu/drm/msm/dsi/dsi_host.c#L1587
[2]
https://elixir.bootlin.com/linux/v6.5-rc2/source/drivers/gpu/drm/msm/dsi/dsi_host.c#L2359
--
With best wishes
Dmitry
--
With best wishes
Dmitry
