linux-kernel - [PATCH 1/2] soundwire: bus: Don't filter slave alerts

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Date:   Thu, 19 Jan 2023 16:51:03 +0000
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     <vkoul@...nel.org>
CC:     <yung-chuan.liao@...ux.intel.com>,
        <pierre-louis.bossart@...ux.intel.com>, <sanyog.r.kale@...el.com>,
        <alsa-devel@...a-project.org>, <linux-kernel@...r.kernel.org>,
        <patches@...nsource.cirrus.com>
Subject: [PATCH 1/2] soundwire: bus: Don't filter slave alerts

Currently the SoundWire core will loop handling slave alerts but it will
only handle those present when the alert was first raised. This causes
some issues with the Cadence SoundWire IP, which only generates an IRQ
when alert changes state. This means that if a new alert arrives whilst
old alerts are being handled it will not be handled in the currently
loop and then no further alerts will be processed since alert never
changes state to trigger a new IRQ.

Correct this issue by allowing the core to handle all pending alerts in
the IRQ handling loop. The code will still only loop up to
SDW_READ_INTR_CLEAR_RETRY times, so it shouldn't be possible for it get
completely stuck and if you are generating IRQs faster than you can
handle them you likely have bigger problems anyway.

Signed-off-by: Charles Keepax <ckeepax@...nsource.cirrus.com>
---
 drivers/soundwire/bus.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index 633d411b64f35..daee2cca94a4d 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -1560,7 +1560,7 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave)
 	unsigned long port;
 	bool slave_notify;
 	u8 sdca_cascade = 0;
-	u8 buf, buf2[2], _buf, _buf2[2];
+	u8 buf, buf2[2];
 	bool parity_check;
 	bool parity_quirk;

@@ -1716,9 +1716,9 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave)
 				"SDW_SCP_INT1 recheck read failed:%d\n", ret);
 			goto io_err;
 		}
-		_buf = ret;
+		buf = ret;

-		ret = sdw_nread_no_pm(slave, SDW_SCP_INTSTAT2, 2, _buf2);
+		ret = sdw_nread_no_pm(slave, SDW_SCP_INTSTAT2, 2, buf2);
 		if (ret < 0) {
 			dev_err(&slave->dev,
 				"SDW_SCP_INT2/3 recheck read failed:%d\n", ret);
@@ -1736,12 +1736,8 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave)
 		}

 		/*
-		 * Make sure no interrupts are pending, but filter to limit loop
-		 * to interrupts identified in the first status read
+		 * Make sure no interrupts are pending
 		 */
-		buf &= _buf;
-		buf2[0] &= _buf2[0];
-		buf2[1] &= _buf2[1];
 		stat = buf || buf2[0] || buf2[1] || sdca_cascade;

 		/*
-- 
2.30.2