Commit 6e06a855 authored Nov 24, 2020 by Pierre-Louis Bossart Committed by Vinod Koul Nov 25, 2020

soundwire: bus: add comments to explain interrupt loop filter

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>

parent b7cab9be

drivers/soundwire/bus.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -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];