Patch "platform/x86: intel_scu_ipc: Check status upon timeout in ipc_wait_for_interrupt()" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    platform/x86: intel_scu_ipc: Check status upon timeout in ipc_wait_for_interrupt()

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     platform-x86-intel_scu_ipc-check-status-upon-timeout.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 50a3864d73eee58e5b3ed1e3516b2ad5b2040649
Author: Stephen Boyd <swboyd@xxxxxxxxxxxx>
Date:   Wed Sep 13 14:27:20 2023 -0700

    platform/x86: intel_scu_ipc: Check status upon timeout in ipc_wait_for_interrupt()
    
    [ Upstream commit 427fada620733e6474d783ae6037a66eae42bf8c ]
    
    It's possible for the completion in ipc_wait_for_interrupt() to timeout,
    simply because the interrupt was delayed in being processed. A timeout
    in itself is not an error. This driver should check the status register
    upon a timeout to ensure that scheduling or interrupt processing delays
    don't affect the outcome of the IPC return value.
    
     CPU0                                                   SCU
     ----                                                   ---
     ipc_wait_for_interrupt()
      wait_for_completion_timeout(&scu->cmd_complete)
      [TIMEOUT]                                             status[IPC_STATUS_BUSY]=0
    
    Fix this problem by reading the status bit in all cases, regardless of
    the timeout. If the completion times out, we'll assume the problem was
    that the IPC_STATUS_BUSY bit was still set, but if the status bit is
    cleared in the meantime we know that we hit some scheduling delay and we
    should just check the error bit.
    
    Cc: Prashant Malani <pmalani@xxxxxxxxxxxx>
    Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
    Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
    Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
    Fixes: ed12f295bfd5 ("ipc: Added support for IPC interrupt mode")
    Signed-off-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230913212723.3055315-3-swboyd@xxxxxxxxxxxx
    Reviewed-by: Hans de Goede <hdegoede@xxxxxxxxxx>
    Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/platform/x86/intel_scu_ipc.c b/drivers/platform/x86/intel_scu_ipc.c
index 96675bea88b10..be97cfae4b0f3 100644
--- a/drivers/platform/x86/intel_scu_ipc.c
+++ b/drivers/platform/x86/intel_scu_ipc.c
@@ -249,10 +249,12 @@ static inline int ipc_wait_for_interrupt(struct intel_scu_ipc_dev *scu)
 {
 	int status;
 
-	if (!wait_for_completion_timeout(&scu->cmd_complete, IPC_TIMEOUT))
-		return -ETIMEDOUT;
+	wait_for_completion_timeout(&scu->cmd_complete, IPC_TIMEOUT);
 
 	status = ipc_read_status(scu);
+	if (status & IPC_STATUS_BUSY)
+		return -ETIMEDOUT;
+
 	if (status & IPC_STATUS_ERR)
 		return -EIO;