linux-kernel - Re: [v1] drm/msm: add shutdown support for display platform

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Message-ID: <219625b5b2cc0eddb2e975d457a2c40d@codeaurora.org>
Date:   Thu, 28 May 2020 14:28:06 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Krishna Manikandan <mkrishn@...eaurora.org>
Cc:     dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        freedreno@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, robdclark@...il.com,
        seanpaul@...omium.org, hoegsberg@...omium.org,
        kalyan_t@...eaurora.org, nganji@...eaurora.org, mka@...omium.org,
        devicetree-owner@...r.kernel.org, robin.murphy@....com
Subject: Re: [v1] drm/msm: add shutdown support for display platform_driver

Hi Krishna,

On 2020-05-28 14:08, Krishna Manikandan wrote:
> Define shutdown callback for display drm driver,
> so as to disable all the CRTCS when shutdown
> notification is received by the driver.
> 

Would be nice to add some more context for adding this shutdown callback
something like below:

If the hardware is still accessing memory after SMMU translation is 
disabled
as part of smmu shutdown callback,  then the IOVAs(I/O virtual address) 
which
it was using will go on the bus as the physical addresses which will 
result
in unknown crashes (NoC/interconnect errors on QCOM SoCs).

PS: Credits for description: Robin Murphy

Thanks,
Sai

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