linux-kernel - Re: [PATCH v3] remoteproc: mediatek: fix side effect of mt8195 sram power on

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Message-ID: <36e7847e-56ed-8768-388e-c6a00a2cb0ec@collabora.com>
Date:   Mon, 14 Mar 2022 12:31:38 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Tinghan Shen <tinghan.shen@...iatek.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Matthias Brugger <matthias.bgg@...il.com>
Cc:     linux-remoteproc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v3] remoteproc: mediatek: fix side effect of mt8195 sram
 power on

Il 14/03/22 12:18, Tinghan Shen ha scritto:
> The definition of L1TCM_SRAM_PDN bits on mt8195 is different to mt8192.
> 
> L1TCM_SRAM_PDN bits[3:0] control the power of mt8195 L1TCM SRAM.
> 
> L1TCM_SRAM_PDN bits[7:4] control the access path to EMI for SCP.
> These bits have to be powered on to allow EMI access for SCP.
> 
> Bits[7:4] also affect audio DSP because audio DSP and SCP are
> placed on the same hardware bus. If SCP cannot access EMI, audio DSP is
> blocked too.
> 
> L1TCM_SRAM_PDN bits[31:8] are not used.
> 
> This fix removes modification of bits[7:4] when power on/off mt8195 SCP
> L1TCM. It's because the modification introduces a short period of time
> blocking audio DSP to access EMI. This was not a problem until we have
> to load both SCP module and audio DSP module. audio DSP needs to access
> EMI because it has source/data on DRAM. Audio DSP will have unexpected
> behavior when it accesses EMI and the SCP driver blocks the EMI path at
> the same time.
> 
> Signed-off-by: Tinghan Shen <tinghan.shen@...iatek.com>


Hello Tinghan,

I'm sorry, but in the last review I forgot to mention that you should
really add a Fixes tag to this commit, since this is.. a fix.

This is the tag that you should use:

Fixes: 79111df414fc ("remoteproc: mediatek: Support mt8195 scp")

After adding that,
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>

> ---
> v3: fix build error
> v2: apply comments about macro definition and function calls
> ---
>   drivers/remoteproc/mtk_common.h |  2 +
>   drivers/remoteproc/mtk_scp.c    | 67 +++++++++++++++++++++++++--------
>   2 files changed, 53 insertions(+), 16 deletions(-)
>