From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755560AbeDZJyH (ORCPT ); Thu, 26 Apr 2018 05:54:07 -0400 Received: from mail.sysgo.com ([176.9.12.79]:55510 "EHLO mail.sysgo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754959AbeDZJyA (ORCPT ); Thu, 26 Apr 2018 05:54:00 -0400 From: David Engraf To: ludovic.desroches@microchip.com Cc: nicolas.ferre@microchip.com, alexandre.belloni@bootlin.com, linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, David Engraf Subject: [PATCH v2] i2c: at91: Read all available bytes at once Date: Thu, 26 Apr 2018 11:53:14 +0200 Message-Id: <20180426095314.12758-1-david.engraf@sysgo.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20180426082558.GX13305@rfolt0960.corp.atmel.com> References: <20180426082558.GX13305@rfolt0960.corp.atmel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 From: david.engraf@sysgo.com (David Engraf) Date: Thu, 26 Apr 2018 11:53:14 +0200 Subject: [PATCH v2] i2c: at91: Read all available bytes at once In-Reply-To: <20180426082558.GX13305@rfolt0960.corp.atmel.com> References: <20180426082558.GX13305@rfolt0960.corp.atmel.com> Message-ID: <20180426095314.12758-1-david.engraf@sysgo.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 --- 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