linux-kernel - Re: [RFT PATCH v2 1/3] drm/bridge: tc358762: Set pre_enable_prev

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Date:   Tue, 28 Feb 2023 03:24:37 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Doug Anderson <dianders@...omium.org>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>
Cc:     dri-devel@...ts.freedesktop.org, Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        freedreno@...ts.freedesktop.org,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Jonas Karlman <jonas@...boo.se>, linux-arm-msm@...r.kernel.org,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <robert.foss@...aro.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Vinod Koul <vkoul@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Sean Paul <sean@...rly.run>, linux-kernel@...r.kernel.org
Subject: Re: [RFT PATCH v2 1/3] drm/bridge: tc358762: Set
 pre_enable_prev_first

On 28/02/2023 02:26, Doug Anderson wrote:
> Hi,
> 
> On Wed, Feb 1, 2023 at 1:51 AM Dave Stevenson
> <dave.stevenson@...pberrypi.com> wrote:
>>
>> On Tue, 31 Jan 2023 at 22:22, Douglas Anderson <dianders@...omium.org> wrote:
>>>
>>> Set the "pre_enable_prev_first" as provided by commit 4fb912e5e190
>>> ("drm/bridge: Introduce pre_enable_prev_first to alter bridge init
>>> order"). This should allow us to revert commit ec7981e6c614
>>> ("drm/msm/dsi: don't powerup at modeset time for parade-ps8640") and
>>> commit 7d8e9a90509f ("drm/msm/dsi: move DSI host powerup to modeset
>>> time").
>>
>> I see no reference in the TC358762 datasheet to requiring the DSI
>> interface to be in any particular state.
>> However, setting this flag does mean that the DSI host doesn't need to
>> power up and down for each host_transfer request from
>> tc358762_pre_enable/tc358762_init, so on that basis I'm good with it.
>>
>> Reviewed-by: Dave Stevenson <dave.stevenson@...pberrypi.com>
>>
>>> Cc: Dave Stevenson <dave.stevenson@...pberrypi.com>
>>> Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>>> Cc: Abhinav Kumar <quic_abhinavk@...cinc.com>
>>> Signed-off-by: Douglas Anderson <dianders@...omium.org>
>>> ---
>>>
>>> (no changes since v1)
>>>
>>>   drivers/gpu/drm/bridge/tc358762.c | 1 +
>>>   1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/gpu/drm/bridge/tc358762.c b/drivers/gpu/drm/bridge/tc358762.c
>>> index 0b6a28436885..77f7f7f54757 100644
>>> --- a/drivers/gpu/drm/bridge/tc358762.c
>>> +++ b/drivers/gpu/drm/bridge/tc358762.c
>>> @@ -229,6 +229,7 @@ static int tc358762_probe(struct mipi_dsi_device *dsi)
>>>          ctx->bridge.funcs = &tc358762_bridge_funcs;
>>>          ctx->bridge.type = DRM_MODE_CONNECTOR_DPI;
>>>          ctx->bridge.of_node = dev->of_node;
>>> +       ctx->bridge.pre_enable_prev_first = true;
>>>
>>>          drm_bridge_add(&ctx->bridge);
> 
> Abhinav asked what the plan was for landing this [1]. Since this isn't
> urgent, I guess the plan is to land patch #1 in drm-misc-next. Then we
> sit and wait until it percolates into mainline and, once it does, then
> patch #2 and #3 can land.
> 
> Since I have Dave's review I can commit this to drm-misc-next myself.
> My plan will be to wait until Thursday or Friday of this week (to give
> people a bit of time to object) and then land patch #1. Then I'll
> snooze things for a while and poke Abhinav and Dmitry to land patch #2
> / #3 when I notice it in mainline. If, at any point, someone comes out
> of the woodwork and yells that this is breaking them then, worst case,
> we can revert.

This plan sounds good to me.

> 
> [1] https://lore.kernel.org/r/1f204585-88e2-abae-1216-92f739ac9e91@quicinc.com/

-- 
With best wishes
Dmitry