linux-kernel - RE: [PATCH] platform/x86: intel_scu_ipc: Keep polling IPC status if it reads IPC_STATUS

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Date:   Thu, 30 Dec 2021 08:30:39 +0000
From:   "Khandelwal, Rajat" <rajat.khandelwal@...el.com>
To:     "mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>,
        "Westerberg, Mika" <mika.westerberg@...el.com>
Subject: RE: [PATCH] platform/x86: intel_scu_ipc: Keep polling IPC status if
 it reads IPC_STATUS_ERR

Hi Mika
I hope this annotation is correct? Sorry for the multiple errors! 

-----Original Message-----
From: Khandelwal, Rajat <rajat.khandelwal@...el.com> 
Sent: Thursday, December 30, 2021 1:54 PM
To: mika.westerberg@...ux.intel.com
Cc: linux-kernel@...r.kernel.org; platform-driver-x86@...r.kernel.org; Khandelwal, Rajat <rajat.khandelwal@...el.com>; Westerberg, Mika <mika.westerberg@...el.com>
Subject: [PATCH] platform/x86: intel_scu_ipc: Keep polling IPC status if it reads IPC_STATUS_ERR

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@...el.com>
---
 drivers/platform/x86/intel_scu_ipc.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/platform/x86/intel_scu_ipc.c b/drivers/platform/x86/intel_scu_ipc.c
index 7cc9089d1e14..1f90acaa7212 100644
--- a/drivers/platform/x86/intel_scu_ipc.c
+++ b/drivers/platform/x86/intel_scu_ipc.c
@@ -233,17 +233,23 @@ 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_BUSY)) {
+			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