linux-kernel - Re: [PATCH 2/3] i2c-axxia: check for error conditions first

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Date:   Tue, 11 Dec 2018 12:02:32 +0000
From:   "Sverdlin, Alexander (Nokia - DE/Ulm)" <alexander.sverdlin@...ia.com>
To:     "Adamski, Krzysztof (Nokia - PL/Wroclaw)" 
        <krzysztof.adamski@...ia.com>, Wolfram Sang <wsa@...-dreams.de>
CC:     "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Tobias Jordan <Tobias.Jordan@...ktrobit.com>,
        Peter Rosin <peda@...ntia.se>
Subject: Re: [PATCH 2/3] i2c-axxia: check for error conditions first

Hi!

On 10/12/2018 16:01, Adamski, Krzysztof (Nokia - PL/Wroclaw) wrote:
> It was observed that when using seqentional mode contrary to the
                                  ^^^^^^^^^^^
> documentation, the SS bit (which is supposed to only be set if
> automatic/sequence command completed normally), is sometimes set
> together with NA (NAK in address phase) causing transfer to falsely be
> considered successful.
> 
> My assumption is that this does not happen during manual mode since the
> controller is stopping its work the moment it sets NA/ND bit in status
> register. This is not the case in Automatic/Sequentional mode where it
                                              ^^^^^^^^^^^^
> is still working to send STOP condition and the actual status we get
> depends on the time when the ISR is run.
> 
> This patch changes the order of checking status bits in ISR - error
> conditions are checked first and only if none of them occurred, the
> transfer may be considered successful. This is required to introduce
> using of sequentional mode in next patch.
           ^^^^^^^^^^^^
sequential

Reviewed-by: Alexander Sverdlin <alexander.sverdlin@...ia.com>

> Signed-off-by: Krzysztof Adamski <krzysztof.adamski@...ia.com>
> ---
>  drivers/i2c/busses/i2c-axxia.c | 32 ++++++++++++++++----------------
>  1 file changed, 16 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-axxia.c b/drivers/i2c/busses/i2c-axxia.c
> index d37caf694fbf..35258321e81b 100644
> --- a/drivers/i2c/busses/i2c-axxia.c
> +++ b/drivers/i2c/busses/i2c-axxia.c
> @@ -296,22 +296,7 @@ static irqreturn_t axxia_i2c_isr(int irq, void *_dev)
>  			i2c_int_disable(idev, MST_STATUS_TFL);
>  	}
>  
> -	if (status & MST_STATUS_SCC) {
> -		/* Stop completed */
> -		i2c_int_disable(idev, ~MST_STATUS_TSS);
> -		complete(&idev->msg_complete);
> -	} else if (status & MST_STATUS_SNS) {
> -		/* Transfer done */
> -		i2c_int_disable(idev, ~MST_STATUS_TSS);
> -		if (i2c_m_rd(idev->msg) && idev->msg_xfrd < idev->msg->len)
> -			axxia_i2c_empty_rx_fifo(idev);
> -		complete(&idev->msg_complete);
> -	} else if (status & MST_STATUS_TSS) {
> -		/* Transfer timeout */
> -		idev->msg_err = -ETIMEDOUT;
> -		i2c_int_disable(idev, ~MST_STATUS_TSS);
> -		complete(&idev->msg_complete);
> -	} else if (unlikely(status & MST_STATUS_ERR)) {
> +	if (unlikely(status & MST_STATUS_ERR)) {
>  		/* Transfer error */
>  		i2c_int_disable(idev, ~0);
>  		if (status & MST_STATUS_AL)
> @@ -328,6 +313,21 @@ static irqreturn_t axxia_i2c_isr(int irq, void *_dev)
>  			readl(idev->base + MST_TX_BYTES_XFRD),
>  			readl(idev->base + MST_TX_XFER));
>  		complete(&idev->msg_complete);
> +	} else if (status & MST_STATUS_SCC) {
> +		/* Stop completed */
> +		i2c_int_disable(idev, ~MST_STATUS_TSS);
> +		complete(&idev->msg_complete);
> +	} else if (status & MST_STATUS_SNS) {
> +		/* Transfer done */
> +		i2c_int_disable(idev, ~MST_STATUS_TSS);
> +		if (i2c_m_rd(idev->msg) && idev->msg_xfrd < idev->msg->len)
> +			axxia_i2c_empty_rx_fifo(idev);
> +		complete(&idev->msg_complete);
> +	} else if (status & MST_STATUS_TSS) {
> +		/* Transfer timeout */
> +		idev->msg_err = -ETIMEDOUT;
> +		i2c_int_disable(idev, ~MST_STATUS_TSS);
> +		complete(&idev->msg_complete);
>  	}
>  
>  out:
> 

-- 
Best regards,
Alexander Sverdlin.