From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755762AbeDZMa6 (ORCPT ); Thu, 26 Apr 2018 08:30:58 -0400 Received: from esa4.microchip.iphmx.com ([68.232.154.123]:57173 "EHLO esa4.microchip.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751713AbeDZMaz (ORCPT ); Thu, 26 Apr 2018 08:30:55 -0400 X-IronPort-AV: E=Sophos;i="5.49,330,1520924400"; d="scan'208";a="13311564" Date: Thu, 26 Apr 2018 14:30:09 +0200 From: Ludovic Desroches To: David Engraf CC: , , , , , Subject: Re: [PATCH v2] i2c: at91: Read all available bytes at once Message-ID: <20180426123009.GZ13305@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: <20180426082558.GX13305@rfolt0960.corp.atmel.com> <20180426095314.12758-1-david.engraf@sysgo.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20180426095314.12758-1-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 On Thu, Apr 26, 2018 at 11:53:14AM +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. > > This patch polls RXRDY and reads all available bytes at > once. > > Signed-off-by: David Engraf Acked-by: Ludovic Desroches Thanks a lot David. Regards Ludovic > --- > drivers/i2c/busses/i2c-at91.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c > index bfd1fdff64a9..9caee5b79eac 100644 > --- a/drivers/i2c/busses/i2c-at91.c > +++ b/drivers/i2c/busses/i2c-at91.c > @@ -518,8 +518,16 @@ 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 by polling RXRDY usable w/ and w/o > + * FIFO. With FIFO enabled we could also read RXFL and avoid polling > + * RXRDY. > + */ > + do { > + at91_twi_read_next_byte(dev); > + } while (at91_twi_read(dev, AT91_TWI_SR) & AT91_TWI_RXRDY); > + } > > /* > * When a NACK condition is detected, the I2C controller sets the NACK, > -- > 2.14.1 >