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: 63c13d61 ("remoteproc/mediatek: add SCP support for mt8183")
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230104083110.736377-1-wenst@chromium.org
[Fixed "Fixes:" tag line]
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

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;
 }