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Reply-To: chi-hsien.lin@cypress.com
Subject: Re: [PATCH 3/6] brcmfmac: reserve 2 credits for host tx control path
To:     Kalle Valo <kvalo@codeaurora.org>
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>
References: <20200609105913.163239-1-chi-hsien.lin@cypress.com>
 <20200609105913.163239-4-chi-hsien.lin@cypress.com>
 <873674o3t3.fsf@codeaurora.org>
From:   Chi-Hsien Lin <chi-hsien.lin@cypress.com>
Message-ID: <d9985b4e-992f-cd08-c2d6-b2b3c3834706@cypress.com>
Date:   Wed, 10 Jun 2020 13:19:04 +0800
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On 06/09/2020 7:51, Kalle Valo wrote:
> 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?

I don't think the casting is necessary since tx_max and tx_seq are both u8.

The code is taken from a similar function data_ok(). I'll remove the 
casting from both functions in V2.


>