linux-kernel - Re: [PATCH] remoteproc/mtk_scp: Move clk ops outside send

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Message-ID: <20230104222213.GB2112402@p14s>
Date:   Wed, 4 Jan 2023 15:22:13 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Chen-Yu Tsai <wenst@...omium.org>
Cc:     Bjorn Andersson <andersson@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-remoteproc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Tinghan Shen <tinghan.shen@...iatek.com>,
        Tzung-Bi Shih <tzungbi@...nel.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Allen-KH Cheng <allen-kh.cheng@...iatek.com>
Subject: Re: [PATCH] remoteproc/mtk_scp: Move clk ops outside send_lock

On Wed, Jan 04, 2023 at 04:31:10PM +0800, Chen-Yu Tsai wrote:
> Clocks are properly reference counted and do not need to be inside the
> lock range.
> 
> Right now this triggers a false-positive lockdep warning on MT8192 based
> Chromebooks, through a combination of mtk-scp that has a cros-ec-rpmsg
> sub-device, the (actual) cros-ec I2C adapter registration, I2C client
> (not on cros-ec) probe doing i2c transfers and enabling clocks.
> 
> This is a false positive because the cros-ec-rpmsg under mtk-scp does
> not have an I2C adapter, and also each I2C adapter and cros-ec instance
> have their own mutex.
> 
> Move the clk operations outside of the send_lock range.

Thanks for providing such a clear explanation - it makes my job a lot easier.

> 
> Fixes: ("63c13d61eafe remoteproc/mediatek: add SCP support for mt8183")

This is the wrong format for a "Fixes:" tag.  Please see
Documentation/process/submitting-patches.rst for details.

> Signed-off-by: Chen-Yu Tsai <wenst@...omium.org>

I have fixed the above and applied this patch.

Thanks,
Mathieu

> ---
>  drivers/remoteproc/mtk_scp_ipi.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/remoteproc/mtk_scp_ipi.c b/drivers/remoteproc/mtk_scp_ipi.c
> index 00f041ebcde6..4c0d121c2f54 100644
> --- a/drivers/remoteproc/mtk_scp_ipi.c
> +++ b/drivers/remoteproc/mtk_scp_ipi.c
> @@ -164,21 +164,21 @@ int scp_ipi_send(struct mtk_scp *scp, u32 id, void *buf, unsigned int len,
>  	    WARN_ON(len > sizeof(send_obj->share_buf)) || WARN_ON(!buf))
>  		return -EINVAL;
>  
> -	mutex_lock(&scp->send_lock);
> -
>  	ret = clk_prepare_enable(scp->clk);
>  	if (ret) {
>  		dev_err(scp->dev, "failed to enable clock\n");
> -		goto unlock_mutex;
> +		return ret;
>  	}
>  
> +	mutex_lock(&scp->send_lock);
> +
>  	 /* Wait until SCP receives the last command */
>  	timeout = jiffies + msecs_to_jiffies(2000);
>  	do {
>  		if (time_after(jiffies, timeout)) {
>  			dev_err(scp->dev, "%s: IPI timeout!\n", __func__);
>  			ret = -ETIMEDOUT;
> -			goto clock_disable;
> +			goto unlock_mutex;
>  		}
>  	} while (readl(scp->reg_base + scp->data->host_to_scp_reg));
>  
> @@ -205,10 +205,9 @@ int scp_ipi_send(struct mtk_scp *scp, u32 id, void *buf, unsigned int len,
>  			ret = 0;
>  	}
>  
> -clock_disable:
> -	clk_disable_unprepare(scp->clk);
>  unlock_mutex:
>  	mutex_unlock(&scp->send_lock);
> +	clk_disable_unprepare(scp->clk);
>  
>  	return ret;
>  }
> -- 
> 2.39.0.314.g84b9a713c41-goog
>