2023년 12월 19일 (화) 오전 11:11, Frieder Schrempf <frieder.schre...@kontron.de>님이
작성:
> On 01.12.23 10:04, Michael Walle wrote:
> >> The FORCE_STOP_STATE bit is unsuitable to force the DSI link into LP-11
> >> mode. It seems the bridge internally queues DSI packets and when the
> >> FORCE_STOP_STATE bit is cleared, they are sent in close succession
> >> without any useful timing (this also means that the DSI lanes won't go
> >> into LP-11 mode). The length of this gibberish varies between 1ms and
> >> 5ms. This sometimes breaks an attached bridge (TI SN65DSI84 in this
> >> case). In our case, the bridge will fail in about 1 per 500 reboots.
> >>
> >> The FORCE_STOP_STATE handling was introduced to have the DSI lanes in
> >> LP-11 state during the .pre_enable phase. But as it turns out, none of
> >> this is needed at all. Between samsung_dsim_init() and
> >> samsung_dsim_set_display_enable() the lanes are already in LP-11 mode.
> >> The code as it was before commit 20c827683de0 ("drm: bridge:
> >> samsung-dsim: Fix init during host transfer") and 0c14d3130654 ("drm:
> >> bridge: samsung-dsim: Fix i.MX8M enable flow to meet spec") was correct
> >> in this regard.
> >>
> >> This patch basically reverts both commits. It was tested on an i.MX8M
> >> SoC with an SN65DSI84 bridge. The signals were probed and the DSI
> >> packets were decoded during initialization and link start-up. After this
> >> patch the first DSI packet on the link is a VSYNC packet and the timing
> >> is correct.
> >>
> >> Command mode between .pre_enable and .enable was also briefly tested by
> >> a quick hack. There was no DSI link partner which would have responded,
> >> but it was made sure the DSI packet was send on the link. As a side
> >> note, the command mode seems to just work in HS mode. I couldn't find
> >> that the bridge will handle commands in LP mode.
> >>
> >> Fixes: 20c827683de0 ("drm: bridge: samsung-dsim: Fix init during host
> >> transfer")
> >> Fixes: 0c14d3130654 ("drm: bridge: samsung-dsim: Fix i.MX8M enable
> >> flow to meet spec")
> >> Signed-off-by: Michael Walle <mwa...@kernel.org>
> >> ---
> >> Let me know wether this should be two commits each reverting one, but
> >> both
> >> commits appeared first in kernel 6.5.
> >
> > Are there any news?
>
> Inki, are you picking this up? Or if not, who will?
>
I can pick it up but it would be better to go to the drm-misc tree. If
nobody cares about it then I will pick it up. :)
acked-by : Inki Dae <inki....@samsung.com>
Thanks,
Inki Dae
