linux-kernel - [PATCH 05/16] soundwire: intel: simplify sync

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Date:   Tue, 14 Mar 2023 09:53:59 +0800
From:   Bard Liao <yung-chuan.liao@...ux.intel.com>
To:     alsa-devel@...a-project.org, vkoul@...nel.org
Cc:     vinod.koul@...aro.org, linux-kernel@...r.kernel.org,
        pierre-louis.bossart@...ux.intel.com, bard.liao@...el.com
Subject: [PATCH 05/16] soundwire: intel: simplify sync_go sequence

From: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>

In the existing code, the SHIM_SYNC::SYNC_GO bit is set, and the code
waits for it to return to zero.

That second wait part is just wrong: the SYNC_GO bit is *write-only* so
there's no way to know if it's cleared by hardware. The code works
because the value for a read-only bit is zero, but that's really just
luck.

Simplify the sequence to a plain read-modify-write.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Reviewed-by: Rander Wang <rander.wang@...el.com>
Signed-off-by: Bard Liao <yung-chuan.liao@...ux.intel.com>
---
 drivers/soundwire/intel.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c
index 2c1c905f8889..6fdb10117e59 100644
--- a/drivers/soundwire/intel.c
+++ b/drivers/soundwire/intel.c
@@ -475,7 +475,6 @@ static int intel_shim_sync_go_unlocked(struct sdw_intel *sdw)
 {
 	void __iomem *shim = sdw->link_res->shim;
 	u32 sync_reg;
-	int ret;
 
 	/* Read SYNC register */
 	sync_reg = intel_readl(shim, SDW_SHIM_SYNC);
@@ -487,13 +486,9 @@ static int intel_shim_sync_go_unlocked(struct sdw_intel *sdw)
 	 */
 	sync_reg |= SDW_SHIM_SYNC_SYNCGO;
 
-	ret = intel_clear_bit(shim, SDW_SHIM_SYNC, sync_reg,
-			      SDW_SHIM_SYNC_SYNCGO);
+	intel_writel(shim, SDW_SHIM_SYNC, sync_reg);
 
-	if (ret < 0)
-		dev_err(sdw->cdns.dev, "SyncGO clear failed: %d\n", ret);
-
-	return ret;
+	return 0;
 }
 
 static int intel_shim_sync_go(struct sdw_intel *sdw)
-- 
2.25.1