+ linux-wireless
Patrick Steinhardt <ps@xxxxxx> writes:
> Starting with v5.3.0, it was observed that throughput of an access point
> with QCA988x-based wireless chip is severely degraded from at least
> 10MB/s to roughly 200KB/s. A bisect of the issue points to commit
> 4504f0e5b571 (ath10k: sdio: workaround firmware UART pin configuration
> bug, 2019-04-19), which employs a workaround for a firmware bug in some
> QCA6174 SDIO devices.
>
> If UART debugging is disabled via the "ath10k.uart_print" module
> parameter, then the UART initialization code is skipped. With the new
> workaround introduced in the mentioned commit, devices that need the
> workaround will also re-set the UART pin of the device to avoid a
> failing SDIO interrupt. But in fact, the change effectively removed the
> early return for all devices that do not use the workaround, and as a
> result UART debugging is now unconditionally turned on disregarding the
> value of "ath10k.uart_print", causing the decrease in throughput.
>
> Fix the issue by re-introducing the early return for all devices again,
> independent of the UART pin workaround. Tests show that throughput is
> back to normal levels again with this fix.
>
> Fixes: 4504f0e5b571 ("ath10k: sdio: workaround firmware UART pin configuration bug")
> Signed-off-by: Patrick Steinhardt <ps@xxxxxx>
> ---
> drivers/net/wireless/ath/ath10k/core.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/ath/ath10k/core.c b/drivers/net/wireless/ath/ath10k/core.c
> index dc45d16e8d21..8e4ca231634d 100644
> --- a/drivers/net/wireless/ath/ath10k/core.c
> +++ b/drivers/net/wireless/ath/ath10k/core.c
> @@ -2125,9 +2125,10 @@ static int ath10k_init_uart(struct ath10k *ar)
> ath10k_warn(ar, "failed to set UART TX pin: %d", ret);
> return ret;
> }
> + }
>
> + if (!uart_print)
> return 0;
> - }
This was fixed in -next with a similar (but not identical) patch, but as
there have been multiple reports of this issues I have now cherry picked
it also for v5.4:
https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/wireless-drivers.git/commit/?id=d79749f7716d9dc32fa2d5075f6ec29aac63c76d
--
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
