On 26/02/2025 12:45, AngeloGioacchino Del Regno wrote:
Il 26/02/25 12:35, Alexandre Mergnat ha scritto:
On 18/02/2025 09:52, AngeloGioacchino Del Regno wrote:
Il 17/02/25 16:03, Alexandre Mergnat ha scritto:
Hi CK.
On 17/02/2025 08:56, CK Hu (胡俊光) wrote:
On Fri, 2025-01-10 at 14:31 +0100, Alexandre Mergnat wrote:
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Currently, mtk_dsi_lane_ready (which setup the DSI lane) is triggered
before mtk_dsi_poweron. lanes_ready flag toggle to true during
mtk_dsi_lane_ready function, and the DSI module is set up during
mtk_dsi_poweron.
Later, during panel driver init, mtk_dsi_lane_ready is triggered but does
nothing because lanes are considered ready. Unfortunately, when the panel
driver try to communicate, the DSI returns a timeout.
The solution found here is to put lanes_ready flag to false after the DSI
module setup into mtk_dsi_poweron to init the DSI lanes after the power /
setup of the DSI module.
I'm not clear about what happen.
I think this DSI flow has worked for a long time.
So only some panel has problem?
I don't know if it's related to a specific panel or not.
And another question.
Do you mean mtk_dsi_lane_ready() do some setting to hardware, but lane is not actually ready?
The workflow should be:
... | dsi->lanes_ready = false | Power-on | setup dsi lanes | dsi->lanes_ready = true (to avoid
re-do dsi lanes setup) | ...
I observe (print function name called + dsi->lanes_ready value):
Alex, the first poweron is called by mtk_dsi_ddp_start() - and the start callback
is internal to the mediatek-drm driver.
That callback is called by mtk_crtc during setup and during bridge enable(), and
there we go with suboptimal code design backfiring - instead of using what the
DRM APIs provide, this driver uses something custom *and* the DRM APIs, giving
this issue.
Part of what mtk_crtc does is duplicated with what the DRM APIs want to do, so
there you go, that's your problem here :-)
Should I go on with describing the next step(s), or is that obvious for everyone?
:-)
Cheers,
Ok thanks Angelo.
Can you let me know if you agree with this change please ? This should be better:
No, no, I'm saying that we should do the exact opposite of what you're doing here!
We should drop the MediaTek custom stuff that duplicates the DRM APIs behavior(s),
and conform to what the DRM APIs provide and want us to do.
To be really really clear - I'm saying to delete and avoid using:
- mtk_dsi_ddp_start()
- mtk_dsi_ddp_stop()
Ok, that what I though first but when I've tried to remove it, the board hung at boot as described
in this old patch:
https://patchwork.kernel.org/project/linux-mediatek/patch/1653012007-11854-3-git-send-email-xinlei.lee@xxxxxxxxxxxx/
Even if I do some little change that (like remove mtk_dsi_start) allow me to boot and make DRM
working for HDMI, DSI still not working at all, I need to do more effort to rework the DSI init.
In my previous suggestion I forgot to say "Since the goal of this serie is to add display support
for genio 350 but not rework/fix DSI driver, is it reasonable to do a soft fix first and then work
on another serie about legacy stuff issue?"
The spirit here should be to use kernel provided APIs, and to make custom stuff
to disappear as much as possible (again, that mtk_crtc .start/.stop).
I'm not saying that literally all of the start/stop callbacks for all of the
MTK DRM drivers should disappear *all at once* but... gradually, one by one,
these should get lost (where/if possible).
Just one more mention: that custom handling also backfired on me while writing
the hdmiv2/dpi drivers... and now backfires on dsi, and in the future it will
backfire again on something else. It's there only to give problems in the end,
not to solve them :-)
Is that issue fixed for DPI ? I'm asking because the following struct still used in mtk_ddp_comp.c:
static const struct mtk_ddp_comp_funcs ddp_dpi = {
.start = mtk_dpi_start,
.stop = mtk_dpi_stop,
.encoder_index = mtk_dpi_encoder_index,
};
But maybe what you fixed for hdmiv2/dpi isn't related to this.
Can you link me the patch where you fix that please ? I think that can help me.
I'm 100% agree with you to remove MediaTek custom stuff that duplicates the DRM APIs behavior. The
genio 350 display support patches has already be stopped and reworked for of graph support, now
stopped by custom framework issue. What do you think about to validate the "DSI hotfix" to merge the
whole series and open a dedicated series to cleanup custom start/stop from MTK DRM framework ? I'm
really asking for your deliberation, not trying to force it when I say I prefer merge this in the
current state :)
--
Regards,
Alexandre
