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Message-ID: <1b1b095e-8fcb-37d5-7542-48a6b55f35a1@quicinc.com>
Date:   Mon, 1 May 2023 13:35:54 +0530
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Subject: Re: [PATCH] spi: spi-geni-qcom: Correct CS_TOGGLE bit in
 SPI_TRANS_CFG
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To:     Konrad Dybcio <konrad.dybcio@linaro.org>, <agross@kernel.org>,
        <andersson@kernel.org>, <broonie@kernel.org>,
        <linux-arm-msm@vger.kernel.org>, <linux-spi@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
CC:     <quic_msavaliy@quicinc.com>, <dianders@chromium.org>,
        <mka@chromium.org>, <swboyd@chromium.org>,
        <quic_vtanuku@quicinc.com>
References: <1682412128-1913-1-git-send-email-quic_vnivarth@quicinc.com>
 <9f28dbff-ca3a-8523-5bfc-37b38bc846c3@linaro.org>
From:   Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com>
In-Reply-To: <9f28dbff-ca3a-8523-5bfc-37b38bc846c3@linaro.org>
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On 4/25/2023 7:15 PM, Konrad Dybcio wrote:
>
> On 4/25/23 09:42, Vijaya Krishna Nivarthi wrote:
>> The CS_TOGGLE bit when set is supposed to instruct FW to
>> toggle CS line between words. The driver with intent of
>> disabling this behaviour has been unsetting BIT(0). This has
>> not caused any trouble so far because the original BIT(1)
>> is untouched and BIT(0) likely wasn't being used.
>>
>> Correct this to prevent a potential future bug.
>>
>> Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com>
>> ---
>
> Has this always been the case, or did the switch to BIT(1)
> only occur on some recent platforms?


Thank you very much for the review..

This has always been the case.

With intent of disabling CS_TOGGLE, currently, the driver is unsetting 
BIT(0), though it should have been BIT(1).

Yet no problem was encountered because

a) BIT(0) seems to be an unused bit

b) BIT(1) is probably already unset because its untouched

Further more, as Doug pointed we are mostly using GPIO for CS.


Testing with the change has not caused any regressions.


Thank you,

Vijay/


>
> Konrad
>
>>   drivers/spi/spi-geni-qcom.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/spi/spi-geni-qcom.c b/drivers/spi/spi-geni-qcom.c
>> index ba7be50..8a7d1c2 100644
>> --- a/drivers/spi/spi-geni-qcom.c
>> +++ b/drivers/spi/spi-geni-qcom.c
>> @@ -35,7 +35,7 @@
>>   #define CS_DEMUX_OUTPUT_SEL    GENMASK(3, 0)
>>     #define SE_SPI_TRANS_CFG    0x25c
>> -#define CS_TOGGLE        BIT(0)
>> +#define CS_TOGGLE        BIT(1)
>>     #define SE_SPI_WORD_LEN        0x268
>>   #define WORD_LEN_MSK        GENMASK(9, 0)