Received-SPF: pass (google.com: domain of linux-wireless-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org CC799C433C6
From:   Kalle Valo <kvalo@codeaurora.org>
To:     Chi-Hsien Lin <chi-hsien.lin@cypress.com>
Cc:     linux-wireless@vger.kernel.org, brcm80211-dev-list@broadcom.com,
        brcm80211-dev-list@cypress.com,
        Arend van Spriel <arend.vanspriel@broadcom.com>,
        Franky Lin <franky.lin@broadcom.com>,
        Hante Meuleman <hante.meuleman@broadcom.com>,
        Wright Feng <wright.feng@cypress.com>,
        Amar Shankar <amsr@cypress.com>,
        Jia-Shyr Chuang <saint.chuang@cypress.com>
Subject: Re: [PATCH 3/6] brcmfmac: reserve 2 credits for host tx control path
References: <20200609105913.163239-1-chi-hsien.lin@cypress.com>
        <20200609105913.163239-4-chi-hsien.lin@cypress.com>
Date:   Tue, 09 Jun 2020 14:51:20 +0300
In-Reply-To: <20200609105913.163239-4-chi-hsien.lin@cypress.com> (Chi-Hsien
        Lin's message of "Tue, 9 Jun 2020 05:59:10 -0500")
Message-ID: <873674o3t3.fsf@codeaurora.org>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-wireless-owner@vger.kernel.org
Precedence: bulk

Chi-Hsien Lin <chi-hsien.lin@cypress.com> writes:

> From: Amar Shankar <amsr@cypress.com>
>
> It is observed that sometimes when sdiod is low in tx credits in low
> rssi scenarios, the data path consumes all sdiod rx all credits and
> there is no sdiod rx credit available for control path causing host
> and card to go out of sync resulting in link loss between host and
> card. So in order to prevent it some credits are reserved for control
> path.
>
> Note that TXCTL_CREDITS can't be larger than the firmware default
> credit update threshold 2; otherwise there will be a deadlock for both
> side waiting for each other.
>
> Signed-off-by: Amar Shankar <amsr@cypress.com>
> Signed-off-by: Jia-Shyr Chuang <saint.chuang@cypress.com>
> Signed-off-by: Chi-Hsien Lin <chi-hsien.lin@cypress.com>
> ---
>  .../wireless/broadcom/brcm80211/brcmfmac/sdio.c   | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
> index ce6f15284277..163bb7f41e44 100644
> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
> @@ -635,6 +635,8 @@ static const struct brcmf_firmware_mapping brcmf_sdio_fwnames[] = {
>  	BRCMF_FW_ENTRY(CY_CC_43012_CHIP_ID, 0xFFFFFFFF, 43012)
>  };
>  
> +#define TXCTL_CREDITS	2
> +
>  static void pkt_align(struct sk_buff *p, int len, int align)
>  {
>  	uint datalign;
> @@ -647,6 +649,14 @@ static void pkt_align(struct sk_buff *p, int len, int align)
>  
>  /* To check if there's window offered */
>  static bool data_ok(struct brcmf_sdio *bus)
> +{
> +	/* Reserve TXCTL_CREDITS credits for txctl */
> +	return (u8)(bus->tx_max - bus->tx_seq) > TXCTL_CREDITS &&
> +	       ((u8)(bus->tx_max - bus->tx_seq) & 0x80) == 0;
> +}

Why casting to u8? Is it really necessary?

-- 
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches