From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755216AbeDYPJ6 (ORCPT ); Wed, 25 Apr 2018 11:09:58 -0400 Received: from esa6.microchip.iphmx.com ([216.71.154.253]:12572 "EHLO esa6.microchip.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755206AbeDYPJz (ORCPT ); Wed, 25 Apr 2018 11:09:55 -0400 X-IronPort-AV: E=Sophos;i="5.49,326,1520924400"; d="scan'208";a="10901281" Date: Wed, 25 Apr 2018 17:08:53 +0200 From: Ludovic Desroches To: David Engraf CC: , , , , , Subject: Re: [PATCH] i2c: at91: Read all available bytes at once Message-ID: <20180425150853.GU13305@rfolt0960.corp.atmel.com> Mail-Followup-To: David Engraf , nicolas.ferre@microchip.com, alexandre.belloni@bootlin.com, linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20180418124055.21333-1-david.engraf@sysgo.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20180418124055.21333-1-david.engraf@sysgo.com> User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > 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 >