linux-kernel - Re: [PATCH v1 1/1] i2c: iproc: Fix i2c master read more than 63 bytes

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Date:   Tue, 30 Jul 2019 13:53:24 -0700
From:   Ray Jui <ray.jui@...adcom.com>
To:     Rayagonda Kokatanur <rayagonda.kokatanur@...adcom.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Cc:     linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCH v1 1/1] i2c: iproc: Fix i2c master read more than 63 bytes

Hi Rayagonda,

On 7/24/2019 1:28 AM, Rayagonda Kokatanur wrote:
> Use SMBUS_MASTER_DATA_READ.MASTER_RD_STATUS bit to check for RX
> FIFO empty condition because SMBUS_MASTER_FIFO_CONTROL.MASTER_RX_PKT_COUNT
> is not updated for read >= 64 bytes. This fixes the issue when trying to
> read from the I2C slave more than 63 bytes.
> 
> Fixes: c24b8d574b7c ("i2c: iproc: Extend I2C read up to 255 bytes")
> 
> Signed-off-by: Rayagonda Kokatanur <rayagonda.kokatanur@...adcom.com>
> ---
>  drivers/i2c/busses/i2c-bcm-iproc.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-bcm-iproc.c b/drivers/i2c/busses/i2c-bcm-iproc.c
> index 2c7f145..d7fd76b 100644
> --- a/drivers/i2c/busses/i2c-bcm-iproc.c
> +++ b/drivers/i2c/busses/i2c-bcm-iproc.c
> @@ -392,16 +392,18 @@ static bool bcm_iproc_i2c_slave_isr(struct bcm_iproc_i2c_dev *iproc_i2c,
>  static void bcm_iproc_i2c_read_valid_bytes(struct bcm_iproc_i2c_dev *iproc_i2c)
>  {
>  	struct i2c_msg *msg = iproc_i2c->msg;
> +	uint32_t val;
>  
>  	/* Read valid data from RX FIFO */
>  	while (iproc_i2c->rx_bytes < msg->len) {
> -		if (!((iproc_i2c_rd_reg(iproc_i2c, M_FIFO_CTRL_OFFSET) >> M_FIFO_RX_CNT_SHIFT)
> -		      & M_FIFO_RX_CNT_MASK))
> +		val = iproc_i2c_rd_reg(iproc_i2c, M_RX_OFFSET);
> +
> +		/* rx fifo empty */
> +		if (!((val >> M_RX_STATUS_SHIFT) & M_RX_STATUS_MASK))
>  			break;
>  
>  		msg->buf[iproc_i2c->rx_bytes] =
> -			(iproc_i2c_rd_reg(iproc_i2c, M_RX_OFFSET) >>
> -			M_RX_DATA_SHIFT) & M_RX_DATA_MASK;
> +			(val >> M_RX_DATA_SHIFT) & M_RX_DATA_MASK;
>  		iproc_i2c->rx_bytes++;
>  	}
>  }
> 

Thanks for the fix. This fix looks good to me!

Reviewed-by: Ray Jui <ray.jui@...adcom.com>