linux-kernel - [PATCH 4/5] soundwire: cadence: fix ACK/NAK handling

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Date:   Fri, 15 Jan 2021 13:37:37 +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, jank@...ence.com,
        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 4/5] soundwire: cadence: fix ACK/NAK handling

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

The existing code reports a NAK only when ACK=0
This is not aligned with the SoundWire 1.x specifications.

Table 32 in the SoundWire 1.2 specification shows that a Device shall
not set NAK=1 if ACK=1. But Table 33 shows the Combined Response
may very well be NAK=1/ACK=1, e.g. if another Device than the one
addressed reports a parity error.

NAK=1 signals a 'Command_Aborted', regardless of the ACK bit value.

Move the tests for NAK so that the NAK=1/ACK=1 combination is properly
detected according to the specification.

Fixes: 956baa1992f9a ('soundwire: cdns: Add sdw_master_ops and IO transfer support')
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@...ux.intel.com>
---
 drivers/soundwire/cadence_master.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
index 801e1fef59d8..d3c9cf920cbd 100644
--- a/drivers/soundwire/cadence_master.c
+++ b/drivers/soundwire/cadence_master.c
@@ -484,10 +484,10 @@ cdns_fill_msg_resp(struct sdw_cdns *cdns,
 		if (!(cdns->response_buf[i] & CDNS_MCP_RESP_ACK)) {
 			no_ack = 1;
 			dev_dbg_ratelimited(cdns->dev, "Msg Ack not received\n");
-			if (cdns->response_buf[i] & CDNS_MCP_RESP_NACK) {
-				nack = 1;
-				dev_err_ratelimited(cdns->dev, "Msg NACK received\n");
-			}
+		}
+		if (cdns->response_buf[i] & CDNS_MCP_RESP_NACK) {
+			nack = 1;
+			dev_err_ratelimited(cdns->dev, "Msg NACK received\n");
 		}
 	}
 
-- 
2.17.1