LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Ludovic Desroches <ludovic.desroches@microchip.com>
To: David Engraf <david.engraf@sysgo.com>
Cc: <ludovic.desroches@microchip.com>, <nicolas.ferre@microchip.com>,
	<alexandre.belloni@bootlin.com>, <linux-i2c@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] i2c: at91: Read all available bytes at once
Date: Wed, 25 Apr 2018 17:08:53 +0200	[thread overview]
Message-ID: <20180425150853.GU13305@rfolt0960.corp.atmel.com> (raw)
In-Reply-To: <20180418124055.21333-1-david.engraf@sysgo.com>

Hi David,

On Wed, Apr 18, 2018 at 02:40:55PM +0200, David Engraf wrote:
> With FIFO enabled it is possible to read multiple bytes
> at once in the interrupt handler as long as RXRDY is
> set. This may also reduce the number of interrupts.
> 
> Signed-off-by: David Engraf <david.engraf@sysgo.com>
> ---
>  drivers/i2c/busses/i2c-at91.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
> index bfd1fdff64a9..d01c2b2384bd 100644
> --- a/drivers/i2c/busses/i2c-at91.c
> +++ b/drivers/i2c/busses/i2c-at91.c
> @@ -518,8 +518,12 @@ static irqreturn_t atmel_twi_interrupt(int irq, void *dev_id)
>  	 * the RXRDY interrupt first in order to not keep garbage data in the
>  	 * Receive Holding Register for the next transfer.
>  	 */
> -	if (irqstatus & AT91_TWI_RXRDY)
> -		at91_twi_read_next_byte(dev);
> +	if (irqstatus & AT91_TWI_RXRDY) {
> +		/* read all available bytes at once when FIFO is used */
> +		do {
> +			at91_twi_read_next_byte(dev);
> +		} while (at91_twi_read(dev, AT91_TWI_SR) & AT91_TWI_RXRDY);

You can avoid this check by using the RXFL field to know the number of
data you can read. Did you try to use it? If yes, did you notice some issues?

Regards

Ludovic

> +	}
>  
>  	/*
>  	 * When a NACK condition is detected, the I2C controller sets the NACK,
> -- 
> 2.14.1
> 

  reply	other threads:[~2018-04-25 15:09 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-18 12:40 David Engraf
2018-04-25 15:08 ` Ludovic Desroches [this message]
2018-04-25 15:43   ` David Engraf
2018-04-26  8:25     ` Ludovic Desroches
2018-04-26  9:53       ` [PATCH v2] " David Engraf
2018-04-26 12:30         ` Ludovic Desroches
2018-04-28 12:38         ` Wolfram Sang
2018-04-30  6:11           ` David Engraf
2018-04-26  5:52   ` [PATCH] " David Engraf

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180425150853.GU13305@rfolt0960.corp.atmel.com \
    --to=ludovic.desroches@microchip.com \
    --cc=alexandre.belloni@bootlin.com \
    --cc=david.engraf@sysgo.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-i2c@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=nicolas.ferre@microchip.com \
    --subject='Re: [PATCH] i2c: at91: Read all available bytes at once' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).