[PATCH v4 2/2] ath10k: start recovery process when payload length exceeds max htc length for sdio

[Wen Gong <wgong@codeaurora.org>]

When simulate random transfer fail for sdio write and read, it happened
"payload length exceeds max htc length" and recovery later sometimes.

Test steps:
1. Add config and update kernel:
CONFIG_FAIL_MMC_REQUEST=y
CONFIG_FAULT_INJECTION=y
CONFIG_FAULT_INJECTION_DEBUG_FS=y

2. Run simulate fail:
cd /sys/kernel/debug/mmc1/fail_mmc_request
echo 10 > probability
echo 10 > times # repeat until hitting issues

3. It happened payload length exceeds max htc length.
[  199.935506] ath10k_sdio mmc1:0001:1: payload length 57005 exceeds max htc length: 4088
....
[  264.990191] ath10k_sdio mmc1:0001:1: payload length 57005 exceeds max htc length: 4088

4. after some time, such as 60 seconds, it start recovery which triggered
by wmi command timeout for periodic scan.
[  269.229232] ieee80211 phy0: Hardware restart was requested
[  269.734693] ath10k_sdio mmc1:0001:1: device successfully recovered

The simulate fail of sdio is not a real sdio transter fail, it only
set an error status in mmc_should_fail_request after the transfer end,
actually the transfer is success, then sdio_io_rw_ext_helper will
return error status and stop transfer the left data. For example,
the really RX len is 286 bytes, then it will split to 2 blocks in
sdio_io_rw_ext_helper, one is 256 bytes, left is 30 bytes, if the
first 256 bytes get an error status by mmc_should_fail_request,then
the left 30 bytes will not read in this RX operation. Then when the
next RX arrive, the left 30 bytes will be considered as the header
of the read, the top 4 bytes of the 30 bytes will be considered as
lookaheads, but actually the 4 bytes is not the lookaheads, so the len
from this lookaheads is not correct, it exceeds max htc length 4088
sometimes. When happened exceeds, the buffer chain is not matched between
firmware and ath10k, then it need to start recovery ASAP. Recently then
recovery will be started by wmi command timeout, but it will be long time
later, for example, it is 60+ seconds later from the periodic scan, if
it does not have periodic scan, it will be longer.

Start recovery when it happened "payload length exceeds max htc length"
will be reasonable.

This patch only effect sdio chips.

Tested with QCA6174 SDIO with firmware WLAN.RMH.4.4.1-00029.

Signed-off-by: Wen Gong <wgong@codeaurora.org>
---
 drivers/net/wireless/ath/ath10k/sdio.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/wireless/ath/ath10k/sdio.c b/drivers/net/wireless/ath/ath10k/sdio.c
index 7b894dcaad2e..f48a56906f71 100644
--- a/drivers/net/wireless/ath/ath10k/sdio.c
+++ b/drivers/net/wireless/ath/ath10k/sdio.c
@@ -557,6 +557,10 @@ static int ath10k_sdio_mbox_rx_alloc(struct ath10k *ar,
 				    le16_to_cpu(htc_hdr->len),
 				    ATH10K_HTC_MBOX_MAX_PAYLOAD_LENGTH);
 			ret = -ENOMEM;
+
+			queue_work(ar->workqueue, &ar->restart_work);
+			ath10k_warn(ar, "exceeds length, start recovery\n");
+
 			goto err;
 		}
 
-- 
2.23.0