From 6e06a85556f9725865af91c9fe502c9669518ed5 Mon Sep 17 00:00:00 2001
From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Date: Tue, 24 Nov 2020 09:33:14 +0800
Subject: [PATCH] soundwire: bus: add comments to explain interrupt loop filter
Git-commit: 6e06a85556f9725865af91c9fe502c9669518ed5
Patch-mainline: v5.11-rc1
References: jsc#SLE-16518
The interrupt handling in SoundWire requires software to re-read the
interrupt status after clearing an interrupt. In case the interrupt is
still outstanding, the code in bus.c will loop a number of times,
however that loop is limited to the interrupts detected in the first
read. This strategy helps meet SoundWire requirements without
remaining forever in an interrupt handler.
Add a couple of comments to document this design.
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20201124013318.8963-2-yung-chuan.liao@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/soundwire/bus.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index ffe4600fd95b..45131b9f5080 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -1334,6 +1334,7 @@ static int sdw_handle_dp0_interrupt(struct sdw_slave *slave, u8 *slave_status)
"SDW_DP0_INT read failed:%d\n", status2);
return status2;
}
+ /* filter to limit loop to interrupts identified in the first status read */
status &= status2;
count++;
@@ -1404,6 +1405,7 @@ static int sdw_handle_port_interrupt(struct sdw_slave *slave,
"SDW_DPN_INT read failed:%d\n", status2);
return status2;
}
+ /* filter to limit loop to interrupts identified in the first status read */
status &= status2;
count++;
@@ -1589,7 +1591,10 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave)
sdca_cascade = ret & SDW_DP0_SDCA_CASCADE;
}
- /* Make sure no interrupts are pending */
+ /*
+ * Make sure no interrupts are pending, but filter to limit loop
+ * to interrupts identified in the first status read
+ */
buf &= _buf;
buf2[0] &= _buf2[0];
buf2[1] &= _buf2[1];
--
2.26.2