#include <linux/debugfs.h>
#include <linux/capability.h>
#include <linux/pm_qos.h>
+#include <linux/wait.h>
#include <asm/iosf_mbi.h>
#define PUNIT_SEMAPHORE_BIT BIT(0)
#define PUNIT_SEMAPHORE_ACQUIRE BIT(1)
-static DEFINE_MUTEX(iosf_mbi_punit_mutex);
-static DEFINE_MUTEX(iosf_mbi_block_punit_i2c_access_count_mutex);
+static DEFINE_MUTEX(iosf_mbi_pmic_access_mutex);
static BLOCKING_NOTIFIER_HEAD(iosf_mbi_pmic_bus_access_notifier);
-static u32 iosf_mbi_block_punit_i2c_access_count;
+static DECLARE_WAIT_QUEUE_HEAD(iosf_mbi_pmic_access_waitq);
+static u32 iosf_mbi_pmic_punit_access_count;
+static u32 iosf_mbi_pmic_i2c_access_count;
static u32 iosf_mbi_sem_address;
static unsigned long iosf_mbi_sem_acquired;
static struct pm_qos_request iosf_mbi_pm_qos;
void iosf_mbi_punit_acquire(void)
{
- mutex_lock(&iosf_mbi_punit_mutex);
+ /* Wait for any I2C PMIC accesses from in kernel drivers to finish. */
+ mutex_lock(&iosf_mbi_pmic_access_mutex);
+ while (iosf_mbi_pmic_i2c_access_count != 0) {
+ mutex_unlock(&iosf_mbi_pmic_access_mutex);
+ wait_event(iosf_mbi_pmic_access_waitq,
+ iosf_mbi_pmic_i2c_access_count == 0);
+ mutex_lock(&iosf_mbi_pmic_access_mutex);
+ }
+ /*
+ * We do not need to do anything to allow the PUNIT to safely access
+ * the PMIC, other then block in kernel accesses to the PMIC.
+ */
+ iosf_mbi_pmic_punit_access_count++;
+ mutex_unlock(&iosf_mbi_pmic_access_mutex);
}
EXPORT_SYMBOL(iosf_mbi_punit_acquire);
void iosf_mbi_punit_release(void)
{
- mutex_unlock(&iosf_mbi_punit_mutex);
+ bool do_wakeup;
+
+ mutex_lock(&iosf_mbi_pmic_access_mutex);
+ iosf_mbi_pmic_punit_access_count--;
+ do_wakeup = iosf_mbi_pmic_punit_access_count == 0;
+ mutex_unlock(&iosf_mbi_pmic_access_mutex);
+
+ if (do_wakeup)
+ wake_up(&iosf_mbi_pmic_access_waitq);
}
EXPORT_SYMBOL(iosf_mbi_punit_release);
* already blocked P-Unit accesses because it wants them blocked over multiple
* i2c-transfers, for e.g. read-modify-write of an I2C client register.
*
- * The P-Unit accesses already being blocked is tracked through the
- * iosf_mbi_block_punit_i2c_access_count variable which is protected by the
- * iosf_mbi_block_punit_i2c_access_count_mutex this mutex is hold for the
- * entire duration of the function.
- *
- * If access is not blocked yet, this function takes the following steps:
+ * To allow safe PMIC i2c bus accesses this function takes the following steps:
*
* 1) Some code sends request to the P-Unit which make it access the PMIC
* I2C bus. Testing has shown that the P-Unit does not check its internal
* PMIC bus semaphore for these requests. Callers of these requests call
* iosf_mbi_punit_acquire()/_release() around their P-Unit accesses, these
- * functions lock/unlock the iosf_mbi_punit_mutex.
- * As the first step we lock the iosf_mbi_punit_mutex, to wait for any in
- * flight requests to finish and to block any new requests.
+ * functions increase/decrease iosf_mbi_pmic_punit_access_count, so first
+ * we wait for iosf_mbi_pmic_punit_access_count to become 0.
+ *
+ * 2) Check iosf_mbi_pmic_i2c_access_count, if access has already
+ * been blocked by another caller, we only need to increment
+ * iosf_mbi_pmic_i2c_access_count and we can skip the other steps.
*
- * 2) Some code makes such P-Unit requests from atomic contexts where it
+ * 3) Some code makes such P-Unit requests from atomic contexts where it
* cannot call iosf_mbi_punit_acquire() as that may sleep.
* As the second step we call a notifier chain which allows any code
* needing P-Unit resources from atomic context to acquire them before
* we take control over the PMIC I2C bus.
*
- * 3) When CPU cores enter C6 or C7 the P-Unit needs to talk to the PMIC
+ * 4) When CPU cores enter C6 or C7 the P-Unit needs to talk to the PMIC
* if this happens while the kernel itself is accessing the PMIC I2C bus
* the SoC hangs.
* As the third step we call pm_qos_update_request() to disallow the CPU
* to enter C6 or C7.
*
- * 4) The P-Unit has a PMIC bus semaphore which we can request to stop
+ * 5) The P-Unit has a PMIC bus semaphore which we can request to stop
* autonomous P-Unit tasks from accessing the PMIC I2C bus while we hold it.
* As the fourth and final step we request this semaphore and wait for our
* request to be acknowledged.
if (WARN_ON(!mbi_pdev || !iosf_mbi_sem_address))
return -ENXIO;
- mutex_lock(&iosf_mbi_block_punit_i2c_access_count_mutex);
+ mutex_lock(&iosf_mbi_pmic_access_mutex);
- if (iosf_mbi_block_punit_i2c_access_count > 0)
+ while (iosf_mbi_pmic_punit_access_count != 0) {
+ mutex_unlock(&iosf_mbi_pmic_access_mutex);
+ wait_event(iosf_mbi_pmic_access_waitq,
+ iosf_mbi_pmic_punit_access_count == 0);
+ mutex_lock(&iosf_mbi_pmic_access_mutex);
+ }
+
+ if (iosf_mbi_pmic_i2c_access_count > 0)
goto success;
- mutex_lock(&iosf_mbi_punit_mutex);
blocking_notifier_call_chain(&iosf_mbi_pmic_bus_access_notifier,
MBI_PMIC_BUS_ACCESS_BEGIN, NULL);
iosf_mbi_sem_acquired = jiffies;
dev_dbg(&mbi_pdev->dev, "P-Unit semaphore acquired after %ums\n",
jiffies_to_msecs(jiffies - start));
- /*
- * Success, keep iosf_mbi_punit_mutex locked till
- * iosf_mbi_unblock_punit_i2c_access() gets called.
- */
goto success;
}
dev_err(&mbi_pdev->dev, "Error P-Unit semaphore timed out, resetting\n");
error:
iosf_mbi_reset_semaphore();
- mutex_unlock(&iosf_mbi_punit_mutex);
-
if (!iosf_mbi_get_sem(&sem))
dev_err(&mbi_pdev->dev, "P-Unit semaphore: %d\n", sem);
success:
if (!WARN_ON(ret))
- iosf_mbi_block_punit_i2c_access_count++;
+ iosf_mbi_pmic_i2c_access_count++;
- mutex_unlock(&iosf_mbi_block_punit_i2c_access_count_mutex);
+ mutex_unlock(&iosf_mbi_pmic_access_mutex);
return ret;
}
void iosf_mbi_unblock_punit_i2c_access(void)
{
- mutex_lock(&iosf_mbi_block_punit_i2c_access_count_mutex);
+ bool do_wakeup = false;
- iosf_mbi_block_punit_i2c_access_count--;
- if (iosf_mbi_block_punit_i2c_access_count == 0) {
+ mutex_lock(&iosf_mbi_pmic_access_mutex);
+ iosf_mbi_pmic_i2c_access_count--;
+ if (iosf_mbi_pmic_i2c_access_count == 0) {
iosf_mbi_reset_semaphore();
- mutex_unlock(&iosf_mbi_punit_mutex);
dev_dbg(&mbi_pdev->dev, "punit semaphore held for %ums\n",
jiffies_to_msecs(jiffies - iosf_mbi_sem_acquired));
+ do_wakeup = true;
}
+ mutex_unlock(&iosf_mbi_pmic_access_mutex);
- mutex_unlock(&iosf_mbi_block_punit_i2c_access_count_mutex);
+ if (do_wakeup)
+ wake_up(&iosf_mbi_pmic_access_waitq);
}
EXPORT_SYMBOL(iosf_mbi_unblock_punit_i2c_access);
int ret;
/* Wait for the bus to go inactive before registering */
- mutex_lock(&iosf_mbi_punit_mutex);
+ iosf_mbi_punit_acquire();
ret = blocking_notifier_chain_register(
&iosf_mbi_pmic_bus_access_notifier, nb);
- mutex_unlock(&iosf_mbi_punit_mutex);
+ iosf_mbi_punit_release();
return ret;
}
int ret;
/* Wait for the bus to go inactive before unregistering */
- mutex_lock(&iosf_mbi_punit_mutex);
+ iosf_mbi_punit_acquire();
ret = iosf_mbi_unregister_pmic_bus_access_notifier_unlocked(nb);
- mutex_unlock(&iosf_mbi_punit_mutex);
+ iosf_mbi_punit_release();
return ret;
}
void iosf_mbi_assert_punit_acquired(void)
{
- WARN_ON(!mutex_is_locked(&iosf_mbi_punit_mutex));
+ WARN_ON(iosf_mbi_pmic_punit_access_count == 0);
}
EXPORT_SYMBOL(iosf_mbi_assert_punit_acquired);
projects / linux.git / commitdiff