On my cherrytrail tablet with axp288 pmic, just doing a bunch of repeated reads from the pmic, e.g. "i2cdump -y 14 0x34" would lookup the tablet in 1 - 3 runs guaranteed. This seems to be causes by the cpuidle / intel_idle driver trying to change the C-state while we hold the punit bus semaphore, at which point everything just hangs. Avoid this by forcing the CPU to C1 before acquiring the punit bus semaphore. BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=109051 Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> --- drivers/i2c/busses/i2c-designware-baytrail.c | 12 ++++++++++++ drivers/i2c/busses/i2c-designware-core.h | 3 +++ drivers/i2c/busses/i2c-designware-platdrv.c | 3 +++ 3 files changed, 18 insertions(+) diff --git a/drivers/i2c/busses/i2c-designware-baytrail.c b/drivers/i2c/busses/i2c-designware-baytrail.c index a419777..4f10ebb 100644 --- a/drivers/i2c/busses/i2c-designware-baytrail.c +++ b/drivers/i2c/busses/i2c-designware-baytrail.c @@ -16,6 +16,7 @@ #include <linux/acpi.h> #include <linux/i2c.h> #include <linux/interrupt.h> +#include <linux/pm_qos.h> #include <asm/iosf_mbi.h> @@ -33,6 +34,13 @@ static int get_sem(struct dw_i2c_dev *dev, u32 *sem) u32 data; int ret; + /* + * Force CPU to C1 state, otherwise if the cpuidle / intel_idle + * driver tries to change the C state while we're holding the + * semaphore, the SoC hangs. + */ + pm_qos_update_request(&dev->pm_qos, 0); + ret = iosf_mbi_read(BT_MBI_UNIT_PMC, MBI_REG_READ, PUNIT_SEMAPHORE, &data); if (ret) { dev_err(dev->dev, "iosf failed to read punit semaphore\n"); @@ -56,6 +64,8 @@ static void reset_semaphore(struct dw_i2c_dev *dev) data &= ~PUNIT_SEMAPHORE_BIT; if (iosf_mbi_write(BT_MBI_UNIT_PMC, MBI_REG_WRITE, PUNIT_SEMAPHORE, data)) dev_err(dev->dev, "iosf failed to reset punit semaphore during write\n"); + + pm_qos_update_request(&dev->pm_qos, PM_QOS_DEFAULT_VALUE); } static int baytrail_i2c_acquire(struct dw_i2c_dev *dev) @@ -143,6 +153,8 @@ int i2c_dw_eval_lock_support(struct dw_i2c_dev *dev) return -EPROBE_DEFER; dev_info(dev->dev, "I2C bus managed by PUNIT\n"); + pm_qos_add_request(&dev->pm_qos, PM_QOS_CPU_DMA_LATENCY, + PM_QOS_DEFAULT_VALUE); dev->acquire_lock = baytrail_i2c_acquire; dev->release_lock = baytrail_i2c_release; dev->pm_runtime_disabled = true; diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h index fb143f5..47d284c 100644 --- a/drivers/i2c/busses/i2c-designware-core.h +++ b/drivers/i2c/busses/i2c-designware-core.h @@ -22,6 +22,7 @@ * */ +#include <linux/pm_qos.h> #define DW_IC_CON_MASTER 0x1 #define DW_IC_CON_SPEED_STD 0x2 @@ -67,6 +68,7 @@ * @fp_lcnt: fast plus LCNT value * @hs_hcnt: high speed HCNT value * @hs_lcnt: high speed LCNT value + * @pm_qos: pm_qos_request used while holding a hardware lock on the bus * @acquire_lock: function to acquire a hardware lock on the bus * @release_lock: function to release a hardware lock on the bus * @pm_runtime_disabled: true if pm runtime is disabled @@ -114,6 +116,7 @@ struct dw_i2c_dev { u16 fp_lcnt; u16 hs_hcnt; u16 hs_lcnt; + struct pm_qos_request pm_qos; int (*acquire_lock)(struct dw_i2c_dev *dev); void (*release_lock)(struct dw_i2c_dev *dev); bool pm_runtime_disabled; diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c index 97a2ca1..6d72929 100644 --- a/drivers/i2c/busses/i2c-designware-platdrv.c +++ b/drivers/i2c/busses/i2c-designware-platdrv.c @@ -291,6 +291,9 @@ static int dw_i2c_plat_remove(struct platform_device *pdev) if (!dev->pm_runtime_disabled) pm_runtime_disable(&pdev->dev); + if (dev->acquire_lock) + pm_qos_remove_request(&dev->pm_qos); + return 0; } -- 2.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
