linux-kernel - Re: [PATCH 10/12] i2c: qup: send NACK for last read sub transfers

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Message-ID: <e34399ec-3668-585c-a931-3b0bc04f0e35@codeaurora.org>
Date:   Tue, 27 Feb 2018 15:07:29 -0700
From:   "Christ, Austin" <austinwc@...eaurora.org>
To:     Abhishek Sahu <absahu@...eaurora.org>,
        Andy Gross <andy.gross@...aro.org>,
        Wolfram Sang <wsa@...-dreams.de>
Cc:     David Brown <david.brown@...aro.org>,
        Sricharan R <sricharan@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 10/12] i2c: qup: send NACK for last read sub transfers

Tested on Centriq 2400

Reviewed-by: Austin Christ <austinwc@...eaurora.org>

On 2/3/2018 12:58 AM, Abhishek Sahu wrote:
> According to I2c specification, “If a master-receiver sends a
> repeated START condition, it sends a not-acknowledge (A) just
> before the repeated START condition”. QUP v2 supports sending
> of NACK without stop with QUP_TAG_V2_DATARD_NACK so added the
> same.
> 
> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
> ---
>   drivers/i2c/busses/i2c-qup.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-qup.c b/drivers/i2c/busses/i2c-qup.c
> index ba717bb..edea3b9 100644
> --- a/drivers/i2c/busses/i2c-qup.c
> +++ b/drivers/i2c/busses/i2c-qup.c
> @@ -113,6 +113,7 @@
>   #define QUP_TAG_V2_DATAWR              0x82
>   #define QUP_TAG_V2_DATAWR_STOP         0x83
>   #define QUP_TAG_V2_DATARD              0x85
> +#define QUP_TAG_V2_DATARD_NACK         0x86
>   #define QUP_TAG_V2_DATARD_STOP         0x87
>   
>   /* Status, Error flags */
> @@ -609,7 +610,9 @@ static int qup_i2c_set_tags(u8 *tags, struct qup_i2c_dev *qup,
>   			tags[len++] = QUP_TAG_V2_DATAWR_STOP;
>   	} else {
>   		if (msg->flags & I2C_M_RD)
> -			tags[len++] = QUP_TAG_V2_DATARD;
> +			tags[len++] = qup->blk.pos == (qup->blk.count - 1) ?
> +				      QUP_TAG_V2_DATARD_NACK :
> +				      QUP_TAG_V2_DATARD;
>   		else
>   			tags[len++] = QUP_TAG_V2_DATAWR;
>   	}
> 

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