From 015497c62a3b21d69640fb48628ec3131b380bc9 Mon Sep 17 00:00:00 2001 From: Richard Fitzgerald Date: Thu, 29 Jan 2026 11:25:15 +0000 Subject: [PATCH] soundwire: cadence: Clear message complete before signalling waiting thread Clear the CDNS_MCP_INT_RX_WL interrupt before signalling completion. This is to prevent the potential race where: - The main thread is scheduled immediately the completion is signalled, and starts a new message - The RX_WL IRQ for this new message happens before sdw_cdns_irq() has been re-scheduled. - When sdw_cdns_irq() is re-scheduled it clears the new RX_WL interrupt. MAIN THREAD | IRQ THREAD | _cdns_xfer_msg() | { | write data to FIFO | wait_for_completion_timeout() | | <---- RX_WL IRQ | sdw_cdns_irq() | { | signal completion <== RESCHEDULE <== Handle message completion | } | | Start new message | _cdns_xfer_msg() | { | write data to FIFO | wait_for_completion_timeout() | | <---- RX_WL IRQ ==> RESCHEDULE ==> | // New RX_WL IRQ is cleared before | // it has been handled. | clear CDNS_MCP_INTSTAT | return IRQ_HANDLED; | } Before this change, this error message was sometimes seen on kernels that have large amounts of debugging enabled: SCP Msg trf timed out This error indicates that the completion has not been signalled after 500ms. Signed-off-by: Richard Fitzgerald Fixes: 956baa1992f9 ("soundwire: cdns: Add sdw_master_ops and IO transfer support") --- drivers/soundwire/cadence_master.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c index eec247b344fb36..247894036d78a6 100644 --- a/drivers/soundwire/cadence_master.c +++ b/drivers/soundwire/cadence_master.c @@ -933,6 +933,14 @@ irqreturn_t sdw_cdns_irq(int irq, void *dev_id) cdns_read_response(cdns); + /* + * Clear interrupt before signalling the completion to avoid + * a race between this thread and the main thread starting + * another TX. + */ + cdns_writel(cdns, CDNS_MCP_INTSTAT, CDNS_MCP_INT_RX_WL); + int_status &= ~CDNS_MCP_INT_RX_WL; + if (defer && defer->msg) { cdns_fill_msg_resp(cdns, defer->msg, defer->length, 0);