6.5-stable review patch. If anyone has any objections, please let me know.
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From: Stephen Boyd swboyd@chromium.org
[ Upstream commit e0b4ab3bb92bda8d12f55842614362989d5b2cb3 ]
It's possible for the polling loop in busy_loop() to get scheduled away for a long time.
status = ipc_read_status(scu); // status = IPC_STATUS_BUSY <long time scheduled away> if (!(status & IPC_STATUS_BUSY))
If this happens, then the status bit could change while the task is scheduled away and this function would never read the status again after timing out. Instead, the function will return -ETIMEDOUT when it's possible that scheduling didn't work out and the status bit was cleared. Bit polling code should always check the bit being polled one more time after the timeout in case this happens.
Fix this by reading the status once more after the while loop breaks. The readl_poll_timeout() macro implements all of this, and it is shorter, so use that macro here to consolidate code and fix this.
There were some concerns with using readl_poll_timeout() because it uses timekeeping, and timekeeping isn't running early on or during the late stages of system suspend or early stages of system resume, but an audit of the code concluded that this code isn't called during those times so it is safe to use the macro.
Cc: Prashant Malani pmalani@chromium.org Reviewed-by: Andy Shevchenko andriy.shevchenko@linux.intel.com Reviewed-by: Mika Westerberg mika.westerberg@linux.intel.com Reviewed-by: Kuppuswamy Sathyanarayanan sathyanarayanan.kuppuswamy@linux.intel.com Fixes: e7b7ab3847c9 ("platform/x86: intel_scu_ipc: Sleeping is fine when polling") Signed-off-by: Stephen Boyd swboyd@chromium.org Link: https://lore.kernel.org/r/20230913212723.3055315-2-swboyd@chromium.org Reviewed-by: Ilpo Järvinen ilpo.jarvinen@linux.intel.com Reviewed-by: Hans de Goede hdegoede@redhat.com Signed-off-by: Hans de Goede hdegoede@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/platform/x86/intel_scu_ipc.c | 19 ++++++++----------- 1 file changed, 8 insertions(+), 11 deletions(-)
diff --git a/drivers/platform/x86/intel_scu_ipc.c b/drivers/platform/x86/intel_scu_ipc.c index 6851d10d65825..4c774ee8bb1bb 100644 --- a/drivers/platform/x86/intel_scu_ipc.c +++ b/drivers/platform/x86/intel_scu_ipc.c @@ -19,6 +19,7 @@ #include <linux/init.h> #include <linux/interrupt.h> #include <linux/io.h> +#include <linux/iopoll.h> #include <linux/module.h> #include <linux/slab.h>
@@ -231,19 +232,15 @@ static inline u32 ipc_data_readl(struct intel_scu_ipc_dev *scu, u32 offset) /* Wait till scu status is busy */ static inline int busy_loop(struct intel_scu_ipc_dev *scu) { - unsigned long end = jiffies + IPC_TIMEOUT; - - do { - u32 status; - - status = ipc_read_status(scu); - if (!(status & IPC_STATUS_BUSY)) - return (status & IPC_STATUS_ERR) ? -EIO : 0; + u8 status; + int err;
- usleep_range(50, 100); - } while (time_before(jiffies, end)); + err = readx_poll_timeout(ipc_read_status, scu, status, !(status & IPC_STATUS_BUSY), + 100, jiffies_to_usecs(IPC_TIMEOUT)); + if (err) + return err;
- return -ETIMEDOUT; + return (status & IPC_STATUS_ERR) ? -EIO : 0; }
/* Wait till ipc ioc interrupt is received or timeout in 10 HZ */