linux-kernel - Re: [PATCH] drm/msm/dpu: always program dsc active bits

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Date:   Fri, 14 Apr 2023 09:35:00 +0200
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     Abhinav Kumar <quic_abhinavk@...cinc.com>
Cc:     Kuogee Hsieh <quic_khsieh@...cinc.com>, robdclark@...il.com,
        sean@...rly.run, swboyd@...omium.org, dianders@...omium.org,
        vkoul@...nel.org, daniel@...ll.ch, airlied@...il.com,
        agross@...nel.org, dmitry.baryshkov@...aro.org,
        andersson@...nel.org, quic_sbillaka@...cinc.com,
        freedreno@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm/dpu: always program dsc active bits

On 2023-04-12 10:33:15, Abhinav Kumar wrote:
[..]
> > What happens if a device boots without DSC panel connected?  Will
> > CTL_DSC_FLUSH be zero and not (unnecessarily, I assume) flush any of the
> > DSC blocks?  Or could this flush uninitialized state to the block?
> > 
> 
> If we bootup without DSC panel connected, the kernel's cfg->dsc will be 
> 0 and default register value of CTL_DSC_FLUSH will be 0 so it wont flush 
> any DSC blocks.

Ack, that makes sense.  However, if I connect a DSC panel, then
disconnect it (now the register should be non-zero, but cfg->dsc will be
zero), and then replug a non-DSC panel multiple times, it'll get flushed
every time because we never clear CTL_DSC_FLUSH after that?

> Sure, as I wrote in the other response, we can move this 
> to reset_intf_cfg later when the other pieces are fixed. And leave a 
> FIXME here.

Kuogee forgot to CC me on this patchs so I did not read/receive that
side of the email thread.  Will catch up before reviewing v2.

- Marijn