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

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Date:   Wed,  4 Jan 2023 16:31:10 +0800
From:   Chen-Yu Tsai <wenst@...omium.org>
To:     Bjorn Andersson <andersson@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Matthias Brugger <matthias.bgg@...il.com>
Cc:     Chen-Yu Tsai <wenst@...omium.org>,
        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: [PATCH] remoteproc/mtk_scp: Move clk ops outside send_lock

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.

Fixes: ("63c13d61eafe remoteproc/mediatek: add SCP support for mt8183")
Signed-off-by: Chen-Yu Tsai <wenst@...omium.org>
---
 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