Re: [PATCH v4 5/5] brcmfmac: sdio: Don't tune while the card is off

[Adrian Hunter <adrian.hunter@intel.com>]

On 14/06/19 2:41 AM, Douglas Anderson wrote:
> When Broadcom SDIO cards are idled they go to sleep and a whole
> separate subsystem takes over their SDIO communication.  This is the
> Always-On-Subsystem (AOS) and it can't handle tuning requests.
> 
> Specifically, as tested on rk3288-veyron-minnie (which reports having
> BCM4354/1 in dmesg), if I force a retune in brcmf_sdio_kso_control()
> when "on = 1" (aka we're transition from sleep to wake) by whacking:
>   bus->sdiodev->func1->card->host->need_retune = 1
> ...then I can often see tuning fail.  In this case dw_mmc reports "All
> phases bad!").  Note that I don't get 100% failure, presumably because
> sometimes the card itself has already transitioned away from the AOS
> itself by the time we try to wake it up.  If I force retuning when "on
> = 0" (AKA force retuning right before sending the command to go to
> sleep) then retuning is always OK.
> 
> NOTE: we need _both_ this patch and the patch to avoid triggering
> tuning due to CRC errors in the sleep/wake transition, AKA ("brcmfmac:
> sdio: Disable auto-tuning around commands expected to fail").  Though
> both patches handle issues with Broadcom's AOS, the problems are
> distinct:
> 1. We want to defer (but not ignore) asynchronous (like
>    timer-requested) tuning requests till the card is awake.  However,
>    we want to ignore CRC errors during the transition, we don't want
>    to queue deferred tuning request.
> 2. You could imagine that the AOS could implement retuning but we
>    could still get errors while transitioning in and out of the AOS.
>    Similarly you could imagine a seamless transition into and out of
>    the AOS (with no CRC errors) even if the AOS couldn't handle
>    tuning.
> 
> ALSO NOTE: presumably there is never a desperate need to retune in
> order to wake up the card, since doing so is impossible.  Luckily the
> only way the card can get into sleep state is if we had a good enough
> tuning to send it a sleep command, so presumably that "good enough"
> tuning is enough to wake us up, at least with a few retries.
> 
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

Acked-by: Adrian Hunter <adrian.hunter@intel.com>

> ---
> 
> Changes in v4:
> - Adjust to API rename (Adrian).
> 
> Changes in v3:
> - ("brcmfmac: sdio: Don't tune while the card is off") new for v3.
> 
> Changes in v2: None
> 
>  drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
> index ee76593259a7..629140b6d7e2 100644
> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
> @@ -669,6 +669,10 @@ brcmf_sdio_kso_control(struct brcmf_sdio *bus, bool on)
>  
>  	sdio_retune_crc_disable(bus->sdiodev->func1);
>  
> +	/* Cannot re-tune if device is asleep; defer till we're awake */
> +	if (on)
> +		sdio_retune_hold_now(bus->sdiodev->func1);
> +
>  	wr_val = (on << SBSDIO_FUNC1_SLEEPCSR_KSO_SHIFT);
>  	/* 1st KSO write goes to AOS wake up core if device is asleep  */
>  	brcmf_sdiod_writeb(bus->sdiodev, SBSDIO_FUNC1_SLEEPCSR, wr_val, &err);
> @@ -729,6 +733,9 @@ brcmf_sdio_kso_control(struct brcmf_sdio *bus, bool on)
>  	if (try_cnt > MAX_KSO_ATTEMPTS)
>  		brcmf_err("max tries: rd_val=0x%x err=%d\n", rd_val, err);
>  
> +	if (on)
> +		sdio_retune_release(bus->sdiodev->func1);
> +
>  	sdio_retune_crc_enable(bus->sdiodev->func1);
>  
>  	return err;
>