RE: [PATCH] Keep polling IPC status if it reads IPC_STATUS_BUSY or IPC_STATUS_ERR until timeout expires

[Khandelwal, Rajat]

Hi @Westerberg, Mika
This was the original message!

-----Original Message-----
From: Khandelwal, Rajat <rajat.khandelwal@xxxxxxxxx> 
Sent: Wednesday, December 29, 2021 7:00 PM
To: mika.westerberg@xxxxxxxxxxxxxxx
Cc: Khandelwal, Rajat <rajat.khandelwal@xxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; platform-driver-x86@xxxxxxxxxxxxxxx
Subject: [PATCH] Keep polling IPC status if it reads IPC_STATUS_BUSY or IPC_STATUS_ERR until timeout expires

The current implementation returns -EIO if and when IPC_STATUS_ERR is returned and returns -ETIMEDOUT even if the status is busy.
This patch polls the IPC status even if IPC_STATUS_ERR is returned until timeout expires and returns -EBUSY if the status shows busy.
Observed in multiple scenarios, trying to fetch the status of IPC after it shows ERR sometimes eradicates the ERR status.

Signed-off-by: Rajat-Khandelwal <rajat.khandelwal@xxxxxxxxx>
---
 drivers/platform/x86/intel_scu_ipc.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/platform/x86/intel_scu_ipc.c b/drivers/platform/x86/intel_scu_ipc.c
index 7cc9089d1e14..91f716e84474 100644
--- a/drivers/platform/x86/intel_scu_ipc.c
+++ b/drivers/platform/x86/intel_scu_ipc.c
@@ -233,17 +233,19 @@ static inline u32 ipc_data_readl(struct intel_scu_ipc_dev *scu, u32 offset)  static inline int busy_loop(struct intel_scu_ipc_dev *scu)  {
 	unsigned long end = jiffies + IPC_TIMEOUT;
+	u32 status;
 
 	do {
-		u32 status;
-
 		status = ipc_read_status(scu);
 		if (!(status & IPC_STATUS_BUSY)) {
-			return (status & IPC_STATUS_ERR) ? -EIO : 0;
+			if (!(status & IPC_STATUS_ERR))
+				return 0;
+		}
 
 		usleep_range(50, 100);
 	} while (time_before(jiffies, end));
 
+	if (status & IPC_STATUS_BUSY)
+		return -EBUSY;
+	if (status & IPC_STATUS_ERR)
+		return -EIO;
+
 	return -ETIMEDOUT;
 }
 
--
2.17.1