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Subject[PATCH 3/7] soundwire: intel: add mutex to prevent concurrent access to SHIM registers
Date
Some of the SHIM registers exposed fields that are link specific, and
in addition some of the power-related registers (SPA/CPA) take time to
be updated. Uncontrolled access leads to timeouts or errors.

Add a mutex, shared by all links, so that all accesses to such
registers are serialized, and follow a pattern of read-modify-write.

The mutex initialization is done at the higher layer since the same
mutex is used for all links.

GitHub issue: https://github.com/thesofproject/linux/issues/1555
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
---
drivers/soundwire/intel.c | 37 +++++++++++++++++++++++++++++++------
drivers/soundwire/intel.h | 2 ++
2 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c
index 1a3b828b03a1..3c271a8044b8 100644
--- a/drivers/soundwire/intel.c
+++ b/drivers/soundwire/intel.c
@@ -286,6 +286,8 @@ static int intel_link_power_up(struct sdw_intel *sdw)
int spa_mask, cpa_mask;
int link_control, ret;

+ mutex_lock(sdw->link_res->shim_lock);
+
/* Link power up sequence */
link_control = intel_readl(shim, SDW_SHIM_LCTL);
spa_mask = (SDW_SHIM_LCTL_SPA << link_id);
@@ -293,6 +295,8 @@ static int intel_link_power_up(struct sdw_intel *sdw)
link_control |= spa_mask;

ret = intel_set_bit(shim, SDW_SHIM_LCTL, link_control, cpa_mask);
+ mutex_unlock(sdw->link_res->shim_lock);
+
if (ret < 0)
return ret;

@@ -307,6 +311,8 @@ static int intel_shim_init(struct sdw_intel *sdw)
int sync_reg, ret;
u16 ioctl = 0, act = 0;

+ mutex_lock(sdw->link_res->shim_lock);
+
/* Initialize Shim */
ioctl |= SDW_SHIM_IOCTL_BKE;
intel_writew(shim, SDW_SHIM_IOCTL(link_id), ioctl);
@@ -351,6 +357,8 @@ static int intel_shim_init(struct sdw_intel *sdw)
sync_reg |= SDW_SHIM_SYNC_SYNCCPU;
ret = intel_clear_bit(shim, SDW_SHIM_SYNC, sync_reg,
SDW_SHIM_SYNC_SYNCCPU);
+ mutex_unlock(sdw->link_res->shim_lock);
+
if (ret < 0)
dev_err(sdw->cdns.dev, "Failed to set sync period: %d\n", ret);

@@ -363,13 +371,15 @@ static void intel_shim_wake(struct sdw_intel *sdw, bool wake_enable)
unsigned int link_id = sdw->instance;
u16 wake_en, wake_sts;

+ mutex_lock(sdw->link_res->shim_lock);
+ wake_en = intel_readw(shim, SDW_SHIM_WAKEEN);
+
if (wake_enable) {
/* Enable the wakeup */
- intel_writew(shim, SDW_SHIM_WAKEEN,
- (SDW_SHIM_WAKEEN_ENABLE << link_id));
+ wake_en |= (SDW_SHIM_WAKEEN_ENABLE << link_id);
+ intel_writew(shim, SDW_SHIM_WAKEEN, wake_en);
} else {
/* Disable the wake up interrupt */
- wake_en = intel_readw(shim, SDW_SHIM_WAKEEN);
wake_en &= ~(SDW_SHIM_WAKEEN_ENABLE << link_id);
intel_writew(shim, SDW_SHIM_WAKEEN, wake_en);

@@ -378,6 +388,7 @@ static void intel_shim_wake(struct sdw_intel *sdw, bool wake_enable)
wake_sts |= (SDW_SHIM_WAKEEN_ENABLE << link_id);
intel_writew(shim, SDW_SHIM_WAKESTS_STATUS, wake_sts);
}
+ mutex_unlock(sdw->link_res->shim_lock);
}

static int intel_link_power_down(struct sdw_intel *sdw)
@@ -387,6 +398,8 @@ static int intel_link_power_down(struct sdw_intel *sdw)
void __iomem *shim = sdw->link_res->shim;
u16 ioctl;

+ mutex_lock(sdw->link_res->shim_lock);
+
/* Glue logic */
ioctl = intel_readw(shim, SDW_SHIM_IOCTL(link_id));
ioctl |= SDW_SHIM_IOCTL_BKE;
@@ -403,6 +416,8 @@ static int intel_link_power_down(struct sdw_intel *sdw)
link_control &= spa_mask;

ret = intel_clear_bit(shim, SDW_SHIM_LCTL, link_control, cpa_mask);
+ mutex_unlock(sdw->link_res->shim_lock);
+
if (ret < 0)
return ret;

@@ -630,11 +645,15 @@ static int intel_pre_bank_switch(struct sdw_bus *bus)
if (!bus->multi_link)
return 0;

+ mutex_lock(sdw->link_res->shim_lock);
+
/* Read SYNC register */
sync_reg = intel_readl(shim, SDW_SHIM_SYNC);
sync_reg |= SDW_SHIM_SYNC_CMDSYNC << sdw->instance;
intel_writel(shim, SDW_SHIM_SYNC, sync_reg);

+ mutex_unlock(sdw->link_res->shim_lock);
+
return 0;
}

@@ -649,6 +668,8 @@ static int intel_post_bank_switch(struct sdw_bus *bus)
if (!bus->multi_link)
return 0;

+ mutex_lock(sdw->link_res->shim_lock);
+
/* Read SYNC register */
sync_reg = intel_readl(shim, SDW_SHIM_SYNC);

@@ -660,9 +681,10 @@ static int intel_post_bank_switch(struct sdw_bus *bus)
*
* So, set the SYNCGO bit only if CMDSYNC bit is set for any Master.
*/
- if (!(sync_reg & SDW_SHIM_SYNC_CMDSYNC_MASK))
- return 0;
-
+ if (!(sync_reg & SDW_SHIM_SYNC_CMDSYNC_MASK)) {
+ ret = 0;
+ goto unlock;
+ }
/*
* Set SyncGO bit to synchronously trigger a bank switch for
* all the masters. A write to SYNCGO bit clears CMDSYNC bit for all
@@ -672,6 +694,9 @@ static int intel_post_bank_switch(struct sdw_bus *bus)

ret = intel_clear_bit(shim, SDW_SHIM_SYNC, sync_reg,
SDW_SHIM_SYNC_SYNCGO);
+unlock:
+ mutex_unlock(sdw->link_res->shim_lock);
+
if (ret < 0)
dev_err(sdw->cdns.dev, "Post bank switch failed: %d\n", ret);

diff --git a/drivers/soundwire/intel.h b/drivers/soundwire/intel.h
index 38b7c125fb10..568c84a80d79 100644
--- a/drivers/soundwire/intel.h
+++ b/drivers/soundwire/intel.h
@@ -15,6 +15,7 @@
* @irq: Interrupt line
* @ops: Shim callback ops
* @dev: device implementing hw_params and free callbacks
+ * @shim_lock: mutex to handle access to shared SHIM registers
*/
struct sdw_intel_link_res {
struct platform_device *pdev;
@@ -25,6 +26,7 @@ struct sdw_intel_link_res {
int irq;
const struct sdw_intel_ops *ops;
struct device *dev;
+ struct mutex *shim_lock; /* protect shared registers */
};

#endif /* __SDW_INTEL_LOCAL_H */
--
2.20.1
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