linux-kernel - Re: [PATCH] i2c: ocores: generate stop condition after timeout in polling mode

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Message-ID: <a937f0c71497b41dc6b7ceb30dc6fdbbed856714.camel@ew.tq-group.com>
Date:   Wed, 12 Apr 2023 11:49:32 +0200
From:   Matthias Schiffer <matthias.schiffer@...tq-group.com>
To:     Peter Korsgaard <peter@...sgaard.com>, Andrew Lunn <andrew@...n.ch>
Cc:     Federico Vaga <federico.vaga@...n.ch>,
        Wolfram Sang <wsa@...nel.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux@...tq-group.com" <linux@...tq-group.com>
Subject: Re: [PATCH] i2c: ocores: generate stop condition after timeout in
 polling mode

On Mon, 2023-02-20 at 16:17 +0000, Matthias Schiffer wrote:
> From: Gregor Herburger <gregor.herburger@...group.com>
> 
> In polling mode, no stop condition is generated after a timeout. This
> causes SCL to remain low and thereby block the bus. If this happens
> during a transfer it can cause slaves to misinterpret the subsequent
> transfer and return wrong values.
> 
> To solve this, pass the ETIMEDOUT error up from ocores_process_polling()
> instead of setting STATE_ERROR directly. The caller is adjusted to call
> ocores_process_timeout() on error both in polling and in IRQ mode, which
> will set STATE_ERROR and generate a stop condition.
> 
> Fixes: 69c8c0c0efa8 ("i2c: ocores: add polling interface")
> Signed-off-by: Gregor Herburger <gregor.herburger@...group.com>
> Signed-off-by: Matthias Schiffer <matthias.schiffer@...tq-group.com>


Any chance we can get someone to have a look at this patch?

Regards,
Matthias



> ---
>  drivers/i2c/busses/i2c-ocores.c | 28 +++++++++++++++-------------
>  1 file changed, 15 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-ocores.c b/drivers/i2c/busses/i2c-ocores.c
> index a0af027db04c1..28bcda3f7040a 100644
> --- a/drivers/i2c/busses/i2c-ocores.c
> +++ b/drivers/i2c/busses/i2c-ocores.c
> @@ -342,18 +342,18 @@ static int ocores_poll_wait(struct ocores_i2c *i2c)
>   * ocores_isr(), we just add our polling code around it.
>   *
>   * It can run in atomic context
> + *
> + * Return: 0 on success, -ETIMEDOUT on timeout
>   */
> -static void ocores_process_polling(struct ocores_i2c *i2c)
> +static int ocores_process_polling(struct ocores_i2c *i2c)
>  {
>  	while (1) {
>  		irqreturn_t ret;
>  		int err;
>  
>  		err = ocores_poll_wait(i2c);
> -		if (err) {
> -			i2c->state = STATE_ERROR;
> -			break; /* timeout */
> -		}
> +		if (err)
> +			return err;
>  
>  		ret = ocores_isr(-1, i2c);
>  		if (ret == IRQ_NONE)
> @@ -364,6 +364,8 @@ static void ocores_process_polling(struct ocores_i2c *i2c)
>  					break;
>  		}
>  	}
> +
> +	return 0;
>  }
>  
>  static int ocores_xfer_core(struct ocores_i2c *i2c,
> @@ -387,16 +389,16 @@ static int ocores_xfer_core(struct ocores_i2c *i2c,
>  	oc_setreg(i2c, OCI2C_DATA, i2c_8bit_addr_from_msg(i2c->msg));
>  	oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_START);
>  
> -	if (polling) {
> -		ocores_process_polling(i2c);
> -	} else {
> +	if (polling)
> +		ret = ocores_process_polling(i2c);
> +	else
>  		ret = wait_event_timeout(i2c->wait,
>  					 (i2c->state == STATE_ERROR) ||
> -					 (i2c->state == STATE_DONE), HZ);
> -		if (ret == 0) {
> -			ocores_process_timeout(i2c);
> -			return -ETIMEDOUT;
> -		}
> +					 (i2c->state == STATE_DONE), HZ) ?
> +						0 : -ETIMEDOUT;
> +	if (ret) {
> +		ocores_process_timeout(i2c);
> +		return ret;
>  	}
>  
>  	return (i2c->state == STATE_DONE) ? num : -EIO;

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