linux-kernel - [PATCH] soundwire: cadence_master: always set CMD

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Date:   Mon, 19 Apr 2021 11:16:06 +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,
        gregkh@...uxfoundation.org, srinivas.kandagatla@...aro.org,
        rander.wang@...ux.intel.com, hui.wang@...onical.com,
        pierre-louis.bossart@...ux.intel.com, sanyog.r.kale@...el.com,
        bard.liao@...el.com
Subject: [PATCH] soundwire: cadence_master: always set CMD_ACCEPT

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

The Cadence IP can be configured in two different ways to deal with
CMD_IGNORED replies to broadcast commands. The CMD_ACCEPT bitfield
controls whether the command is discarded or if the IP proceeds with
the change (typically a bank switch or clock stop command).

The existing code seems to be inconsistent:
a) For some historical reason, we set this CMD_ACCEPT bitfield during
the initialization, but we don't during a resume from a clock-stoppped
state.
b) In addition, the loop used in the clock-stop sequence is quite
racy, it's possible that a device has lost sync but it's still tagged
as ATTACHED.
c) If somehow a Device loses sync and is unable to ack a broadcast
command, we do not have an error handling mechanism anyways. The IP
should go ahead and let the Device regain sync at a later time.

Make sure the CMD_ACCEPT bit is always set.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@...ux.intel.com>
Reviewed-by: Rander Wang <rander.wang@...el.com>
Signed-off-by: Bard Liao <yung-chuan.liao@...ux.intel.com>
---
 drivers/soundwire/cadence_master.c | 21 ++-------------------
 1 file changed, 2 insertions(+), 19 deletions(-)

diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
index 192dac10f0c2..25950422b085 100644
--- a/drivers/soundwire/cadence_master.c
+++ b/drivers/soundwire/cadence_master.c
@@ -1428,20 +1428,6 @@ int sdw_cdns_clock_stop(struct sdw_cdns *cdns, bool block_wake)
 		}
 	}
 
-	/*
-	 * This CMD_ACCEPT should be used when there are no devices
-	 * attached on the link when entering clock stop mode. If this is
-	 * not set and there is a broadcast write then the command ignored
-	 * will be treated as a failure
-	 */
-	if (!slave_present)
-		cdns_updatel(cdns, CDNS_MCP_CONTROL,
-			     CDNS_MCP_CONTROL_CMD_ACCEPT,
-			     CDNS_MCP_CONTROL_CMD_ACCEPT);
-	else
-		cdns_updatel(cdns, CDNS_MCP_CONTROL,
-			     CDNS_MCP_CONTROL_CMD_ACCEPT, 0);
-
 	/* commit changes */
 	ret = cdns_config_update(cdns);
 	if (ret < 0) {
@@ -1508,11 +1494,8 @@ int sdw_cdns_clock_restart(struct sdw_cdns *cdns, bool bus_reset)
 	cdns_updatel(cdns, CDNS_MCP_CONTROL,
 		     CDNS_MCP_CONTROL_BLOCK_WAKEUP, 0);
 
-	/*
-	 * clear CMD_ACCEPT so that the command ignored
-	 * will be treated as a failure during a broadcast write
-	 */
-	cdns_updatel(cdns, CDNS_MCP_CONTROL, CDNS_MCP_CONTROL_CMD_ACCEPT, 0);
+	cdns_updatel(cdns, CDNS_MCP_CONTROL, CDNS_MCP_CONTROL_CMD_ACCEPT,
+		     CDNS_MCP_CONTROL_CMD_ACCEPT);
 
 	if (!bus_reset) {
 
-- 
2.17.1