diff mbox

ath10k: Delay device access after cold reset

Message ID 1435904142-30295-1-git-send-email-vthiagar@qti.qualcomm.com (mailing list archive)
State Changes Requested
Headers show

Commit Message

Vasanthakumar Thiagarajan July 3, 2015, 6:15 a.m. UTC 
It is observed that during cold reset pcie access right
after a write operation to SOC_GLOBAL_RESET_ADDRESS causes
Data Bus Error and system hard lockup. The reason
for bus error is that pcie needs some time to get
back to stable state for any transaction during cold reset. Add
delay of 20 msecs after write of SOC_GLOBAL_RESET_ADDRESS
to fix this issue.

Signed-off-by: Vasanthakumar Thiagarajan <vthiagar@qti.qualcomm.com>
---
 drivers/net/wireless/ath/ath10k/pci.c | 20 +++++++-------------
 1 file changed, 7 insertions(+), 13 deletions(-)

Comments

Kalle Valo July 10, 2015, 8:48 a.m. UTC | #1 
Vasanthakumar Thiagarajan <vthiagar@qti.qualcomm.com> writes:

> It is observed that during cold reset pcie access right
> after a write operation to SOC_GLOBAL_RESET_ADDRESS causes
> Data Bus Error and system hard lockup. The reason
> for bus error is that pcie needs some time to get
> back to stable state for any transaction during cold reset. Add
> delay of 20 msecs after write of SOC_GLOBAL_RESET_ADDRESS
> to fix this issue.
>
> Signed-off-by: Vasanthakumar Thiagarajan <vthiagar@qti.qualcomm.com>

On what devices did you test this? That should be documented in the
commit log.
diff mbox

Patch

diff --git a/drivers/net/wireless/ath/ath10k/pci.c b/drivers/net/wireless/ath/ath10k/pci.c
index 1b4634a..130746b 100644
--- a/drivers/net/wireless/ath/ath10k/pci.c
+++ b/drivers/net/wireless/ath/ath10k/pci.c
@@ -2761,7 +2761,6 @@  static int ath10k_pci_wait_for_target_init(struct ath10k *ar)
 
 static int ath10k_pci_cold_reset(struct ath10k *ar)
 {
-	int i;
 	u32 val;
 
 	ath10k_dbg(ar, ATH10K_DBG_BOOT, "boot cold reset\n");
@@ -2777,23 +2776,18 @@  static int ath10k_pci_cold_reset(struct ath10k *ar)
 	val |= 1;
 	ath10k_pci_reg_write32(ar, SOC_GLOBAL_RESET_ADDRESS, val);
 
-	for (i = 0; i < ATH_PCI_RESET_WAIT_MAX; i++) {
-		if (ath10k_pci_reg_read32(ar, RTC_STATE_ADDRESS) &
-					  RTC_STATE_COLD_RESET_MASK)
-			break;
-		msleep(1);
-	}
+	/* After writing into SOC_GLOBAL_RESET to put device into
+	 * reset and pulling out of reset pcie may not be stable
+	 * for any immediate pcie register access and cause bus error,
+	 * add delay before any pcie access request to fix this issue.
+	 */
+	msleep(20);
 
 	/* Pull Target, including PCIe, out of RESET. */
 	val &= ~1;
 	ath10k_pci_reg_write32(ar, SOC_GLOBAL_RESET_ADDRESS, val);
 
-	for (i = 0; i < ATH_PCI_RESET_WAIT_MAX; i++) {
-		if (!(ath10k_pci_reg_read32(ar, RTC_STATE_ADDRESS) &
-					    RTC_STATE_COLD_RESET_MASK))
-			break;
-		msleep(1);
-	}
+	msleep(20);
 
 	ath10k_dbg(ar, ATH10K_DBG_BOOT, "boot cold reset complete\n");