linux-kernel - Re: [PATCH] i2c: at91: handle TXRDY interrupt spam

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Message-ID: <20190429090005.f6ydghzu5n5yruav@M43218.corp.atmel.com>
Date:   Mon, 29 Apr 2019 11:00:05 +0200
From:   Ludovic Desroches <ludovic.desroches@...rochip.com>
To:     Raag Jadav <raagjadav@...il.com>
CC:     <linux-i2c@...r.kernel.org>, <nicolas.ferre@...rochip.com>,
        <alexandre.belloni@...tlin.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] i2c: at91: handle TXRDY interrupt spam

Hello Raag,

On Tue, Apr 23, 2019 at 01:06:48PM +0530, Raag Jadav wrote:
> External E-Mail
> 
> 
> Performing i2c write operation while SDA or SCL line is held
> or grounded by slave device, we go into infinite at91_twi_write_next_byte
> loop with TXRDY interrupt spam.

Sorry but I am not sure to have the full picture, the controller is in
slave or master mode?

SVREAD is only used in slave mode. When SVREAD is set, it means that a read
access is performed and your issue concerns the write operation.

Regards

Ludovic

> 
> Signed-off-by: Raag Jadav <raagjadav@...il.com>
> ---
>  drivers/i2c/busses/i2c-at91.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
> index 3f3e8b3..b2f5fdb 100644
> --- a/drivers/i2c/busses/i2c-at91.c
> +++ b/drivers/i2c/busses/i2c-at91.c
> @@ -72,6 +72,7 @@
>  #define	AT91_TWI_TXCOMP		BIT(0)	/* Transmission Complete */
>  #define	AT91_TWI_RXRDY		BIT(1)	/* Receive Holding Register Ready */
>  #define	AT91_TWI_TXRDY		BIT(2)	/* Transmit Holding Register Ready */
> +#define	AT91_TWI_SVREAD		BIT(3)	/* Slave Read */
>  #define	AT91_TWI_OVRE		BIT(6)	/* Overrun Error */
>  #define	AT91_TWI_UNRE		BIT(7)	/* Underrun Error */
>  #define	AT91_TWI_NACK		BIT(8)	/* Not Acknowledged */
> @@ -571,7 +572,10 @@ static irqreturn_t atmel_twi_interrupt(int irq, void *dev_id)
>  		at91_disable_twi_interrupts(dev);
>  		complete(&dev->cmd_complete);
>  	} else if (irqstatus & AT91_TWI_TXRDY) {
> -		at91_twi_write_next_byte(dev);
> +		if ((status & AT91_TWI_SVREAD) && (dev->buf_len == 0))
> +			at91_twi_write(dev, AT91_TWI_IDR, AT91_TWI_TXRDY);
> +		else
> +			at91_twi_write_next_byte(dev);
>  	}
>  
>  	/* catch error flags */
> -- 
> 2.7.4
> 
>