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Subject[PATCH 07/16] soundwire: cadence: mask Slave interrupt before stopping clock
Date
Intel QA reported a very rare case, possibly hardware-dependent, where
a Slave can become UNATTACHED during a clock stop sequence, which
leads to timeouts and failed suspend sequences.

This patch suppresses the handling of all Slave events while this
transition happens. The two cases that matter are:

a) alerts: if the Slave wants to signal an alert condition, it can do
so using the in-band wake, so there's almost no impact with this
patch.

b) sync loss or imp-def reset: in those cases, bringing back the Slave
to functional state requires a complete re-enumeration. It's better to
just ignore this case and restart cleanly, rather than attempt a
'clean' suspend.

Validation results show the timeouts no longer visible with this patch.

GitHub issue: https://github.com/thesofproject/linux/issues/1678
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
---
drivers/soundwire/cadence_master.c | 28 ++++++++++++++++++++++++++++
1 file changed, 28 insertions(+)

diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
index 02f18ce6b7e7..a4ba57f44c1f 100644
--- a/drivers/soundwire/cadence_master.c
+++ b/drivers/soundwire/cadence_master.c
@@ -865,6 +865,24 @@ int sdw_cdns_exit_reset(struct sdw_cdns *cdns)
}
EXPORT_SYMBOL(sdw_cdns_exit_reset);

+/**
+ * sdw_cdns_enable_slave_interrupt() - Enable SDW slave interrupts
+ * @cdns: Cadence instance
+ * @state: boolean for true/false
+ */
+static void cdns_enable_slave_interrupts(struct sdw_cdns *cdns, bool state)
+{
+ u32 mask;
+
+ mask = cdns_readl(cdns, CDNS_MCP_INTMASK);
+ if (state)
+ mask |= CDNS_MCP_INT_SLAVE_MASK;
+ else
+ mask &= ~CDNS_MCP_INT_SLAVE_MASK;
+
+ cdns_writel(cdns, CDNS_MCP_INTMASK, mask);
+}
+
/**
* sdw_cdns_enable_interrupt() - Enable SDW interrupts
* @cdns: Cadence instance
@@ -1272,6 +1290,13 @@ int sdw_cdns_clock_stop(struct sdw_cdns *cdns, bool block_wake)
return 1;
}

+ /*
+ * Before entering clock stop we mask the Slave
+ * interrupts. This helps avoid having to deal with e.g. a
+ * Slave becoming UNATTACHED while the clock is being stopped
+ */
+ cdns_enable_slave_interrupts(cdns, false);
+
/*
* For specific platforms, it is required to be able to put
* master into a state in which it ignores wake-up trials
@@ -1349,6 +1374,9 @@ int sdw_cdns_clock_restart(struct sdw_cdns *cdns, bool bus_reset)
{
int ret;

+ /* unmask Slave interrupts that were masked when stopping the clock */
+ cdns_enable_slave_interrupts(cdns, true);
+
ret = cdns_clear_bit(cdns, CDNS_MCP_CONTROL,
CDNS_MCP_CONTROL_CLK_STOP_CLR);
if (ret < 0) {
--
2.20.1
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