[PATCH v2] ath10k: Fix the MTU size on QCA9377 SDIO

[Fabio Estevam]

On an imx6dl-pico-pi board with a QCA9377 SDIO chip, simply trying to
connect via ssh to another machine causes:

[   55.824159] ath10k_sdio mmc1:0001:1: failed to transmit packet, dropping: -12
[   55.832169] ath10k_sdio mmc1:0001:1: failed to submit frame: -12
[   55.838529] ath10k_sdio mmc1:0001:1: failed to push frame: -12
[   55.905863] ath10k_sdio mmc1:0001:1: failed to transmit packet, dropping: -12
[   55.913650] ath10k_sdio mmc1:0001:1: failed to submit frame: -12
[   55.919887] ath10k_sdio mmc1:0001:1: failed to push frame: -12

, leading to an ssh connection failure.

One user inspected the size of frames on Wireshark and reported
the followig:

"I was able to narrow the issue down to the mtu. If I set the mtu for
the wlan0 device to 1486 instead of 1500, the issue does not happen.

The size of frames that I see on Wireshark is exactly 1500 after
setting it to 1486."

Clearing the HI_ACS_FLAGS_ALT_DATA_CREDIT_SIZE avoids the problem and
the ssh command works successfully after that.

Introduce a 'credit_size_workaround' field to ath10k_hw_params for
the QCA9377 SDIO, so that the HI_ACS_FLAGS_ALT_DATA_CREDIT_SIZE
is not set in this case.

Tested with QCA9377 SDIO with firmware WLAN.TF.1.1.1-00061-QCATFSWPZ-1.

Fixes: 2f918ea98606 ("ath10k: enable alt data of TX path for sdio")
Signed-off-by: Fabio Estevam <festevam at denx.de>
---
Changes since v1:
- Restrict the workaround only for QCA9377 SDIO

 drivers/net/wireless/ath/ath10k/core.c | 3 ++-
 drivers/net/wireless/ath/ath10k/hw.h   | 3 +++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/ath10k/core.c b/drivers/net/wireless/ath/ath10k/core.c
index 72a366aa9f60..5a936e643d7a 100644
--- a/drivers/net/wireless/ath/ath10k/core.c
+++ b/drivers/net/wireless/ath/ath10k/core.c
@@ -715,6 +715,7 @@ static void ath10k_send_suspend_complete(struct ath10k *ar)
 
 static int ath10k_init_sdio(struct ath10k *ar, enum ath10k_firmware_mode mode)
 {
+	bool mtu_workaround = ar->hw_params.credit_size_workaround;
 	int ret;
 	u32 param = 0;
 
@@ -732,7 +733,7 @@ static int ath10k_init_sdio(struct ath10k *ar, enum ath10k_firmware_mode mode)
 
 	param |= HI_ACS_FLAGS_SDIO_REDUCE_TX_COMPL_SET;
 
-	if (mode == ATH10K_FIRMWARE_MODE_NORMAL)
+	if (mode == ATH10K_FIRMWARE_MODE_NORMAL && !mtu_workaround)
 		param |= HI_ACS_FLAGS_ALT_DATA_CREDIT_SIZE;
 	else
 		param &= ~HI_ACS_FLAGS_ALT_DATA_CREDIT_SIZE;
diff --git a/drivers/net/wireless/ath/ath10k/hw.h b/drivers/net/wireless/ath/ath10k/hw.h
index 6b03c7787e36..591ef7416b61 100644
--- a/drivers/net/wireless/ath/ath10k/hw.h
+++ b/drivers/net/wireless/ath/ath10k/hw.h
@@ -618,6 +618,9 @@ struct ath10k_hw_params {
 	 */
 	bool uart_pin_workaround;
 
+	/* Workaround for the credit size calculation */
+	bool credit_size_workaround;
+
 	/* tx stats support over pktlog */
 	bool tx_stats_over_pktlog;
 
-- 
2.25.1