soundwire: cadence: recheck device0 attachment after status change

This patch adds a status check after device0 attachment to solve race
conditions observed during attachment with multiple devices per link

The sequence is the following

1) deviceA attaches as device0

2) the hardware detects a device0 status change and throws an
 interrupt.

3) the interrupt handler schedules the work function

4) the workqueue starts, we read the status
slave0 = cdns_readl(cdns, CDNS_MCP_SLAVE_INTSTAT0);
slave1 = cdns_readl(cdns, CDNS_MCP_SLAVE_INTSTAT1);

we deal with the status change and program deviceA device number to a
non-zero value.

5) deviceB attaches as device0, the device0 status seen by the
hardware does not change.

6) we clear the CDNS_MCP_SLAVE_INTSTAT0/1 registers -> we will never detect
deviceB!

This patch suggest re-checking in a loop the device0 status with a
PING frame, i.e. using the real device0 status instead of information
on status changes.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20220420023039.14144-1-yung-chuan.liao@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

0 files changed, 0 insertions, 0 deletions