linux-kernel - Re: [PATCH v2 05/11] clk: qcom: gcc-msm8998: Mark gpu_cfg_ahb

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Date:   Mon, 08 Feb 2021 10:18:40 -0800
From:   Stephen Boyd <sboyd@...nel.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        linux-arm-msm@...r.kernel.org
Cc:     konrad.dybcio@...ainline.org, marijn.suijten@...ainline.org,
        martin.botka@...ainline.org, phone-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org, agross@...nel.org,
        bjorn.andersson@...aro.org, mturquette@...libre.com,
        robh+dt@...nel.org, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>
Subject: Re: [PATCH v2 05/11] clk: qcom: gcc-msm8998: Mark gpu_cfg_ahb_clk as critical

Quoting AngeloGioacchino Del Regno (2021-01-14 14:10:53)
> The GPU IOMMU depends on this clock and the hypervisor will crash
> the SoC if this clock gets disabled because the secure contexts
> that have been set on this IOMMU by the bootloader will become
> unaccessible (or they get reset).
> Mark this clock as critical to avoid this issue when the Adreno
> GPU is enabled.
> 
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...ainline.org>
> ---
>  drivers/clk/qcom/gcc-msm8998.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/clk/qcom/gcc-msm8998.c b/drivers/clk/qcom/gcc-msm8998.c
> index c8d4c0348952..afea60a3ef43 100644
> --- a/drivers/clk/qcom/gcc-msm8998.c
> +++ b/drivers/clk/qcom/gcc-msm8998.c
> @@ -2081,6 +2081,12 @@ static struct clk_branch gcc_gpu_cfg_ahb_clk = {
>                 .hw.init = &(struct clk_init_data){
>                         .name = "gcc_gpu_cfg_ahb_clk",
>                         .ops = &clk_branch2_ops,
> +                       /*
> +                        * The GPU IOMMU depends on this clock and hypervisor
> +                        * will crash the SoC if this clock goes down, due to
> +                        * secure contexts protection.
> +                        */
> +                       .flags = CLK_IS_CRITICAL,
>                 },
>         },

Please send a followup patch that hits the branch on at probe time and
removes this clk from the kernel. That will save some memory and
overhead of worrying about this clk.