linux-kernel - Re: [PATCH RFC 3/4] i2c: at91: added slave mode support

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Message-ID: <20171101130417.GA17787@jfi-dev>
Date:   Wed, 1 Nov 2017 14:04:18 +0100
From:   Juergen Fitschen <me@....yt>
To:     Ludovic Desroches <ludovic.desroches@...rochip.com>
Cc:     Wolfram Sang <wsa@...-dreams.de>, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 3/4] i2c: at91: added slave mode support

Helle Ludovic,

while going through this patch a question related to the Atmel / Microchip HW
came into mind:

On Fri, Oct 27, 2017 at 05:12:00PM +0200, Juergen Fitschen wrote:
> diff --git a/drivers/i2c/busses/i2c-at91.h b/drivers/i2c/busses/i2c-at91.h
> (...)
>  #define	AT91_TWI_INT_MASK \
> -	(AT91_TWI_TXCOMP | AT91_TWI_RXRDY | AT91_TWI_TXRDY | AT91_TWI_NACK)
> +	(AT91_TWI_TXCOMP | AT91_TWI_RXRDY | AT91_TWI_TXRDY | AT91_TWI_NACK \
> +	| AT91_TWI_SVACC | AT91_TWI_EOSACC)

The AT91_TWI_INT_MASK is used to disable all interrputs in the
at91_disable_twi_interrupts function by writing the mask to the interrupt
disable register (IDR). I wonder what happens on MPUs that don't have
AT91_TWI_SVACC and AT91_TWI_EOSACC implemented, like the AT91RM9200? Do you
think we should revise this and write specific masks depending on the current
moude the I2C HW is in?

Something like this:

void at91_disable_twi_interrupts(struct at91_twi_dev *dev)
{
        if (dev->slave_detected)
                at91_twi_write(dev, AT91_TWI_IDR, AT91_TWI_INT_MASK_SLAVE);
        else
                at91_twi_write(dev, AT91_TWI_IDR, AT91_TWI_INT_MASK_MASTER);
}


Best regards
  Juergen