From: David Engraf <david.engraf@sysgo.com> To: Ludovic Desroches <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 Subject: Re: [PATCH] i2c: at91: Read all available bytes at once Date: Thu, 26 Apr 2018 07:52:17 +0200 [thread overview] Message-ID: <ddc4beb3-5620-dc69-5b16-bce2737fb59f@sysgo.com> (raw) In-Reply-To: <20180425150853.GU13305@rfolt0960.corp.atmel.com> Hi Ludovic, Am 25.04.2018 um 17:08 schrieb Ludovic Desroches: > 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? I did a quick test by reading RXFL and it worked as well but I decided to use the more readable solution by polling RXRDY. Also I don't need to check if the FIFO has been enabled. If you prefer using RXFL I can create a new patch. Best regards - David > Regards > > Ludovic > >> + } >> >> /* >> * When a NACK condition is detected, the I2C controller sets the NACK, >> -- >> 2.14.1 >> -- Mit freundlichen Grüßen/Best regards, David Engraf Product Engineer SYSGO AG Office Mainz Am Pfaffenstein 14 / D-55270 Klein-Winternheim / Germany Phone: +49-6136-9948-0 / Fax: +49-6136-9948-10 E-mail: david.engraf@sysgo.com _________________________________________________________________________________ Web: https://www.sysgo.com Blog: https://www.sysgo.com/blog Events: https://www.sysgo.com/events Newsletter: https://www.sysgo.com/newsletter _________________________________________________________________________________ Handelsregister/Commercial Registry: HRB Mainz 90 HRB 8066 Vorstand/Executive Board: Etienne Butery (CEO), Kai Sablotny (COO) Aufsichtsratsvorsitzender/Supervisory Board Chairman: Marc Darmon USt-Id-Nr./VAT-Id-No.: DE 149062328
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From: david.engraf@sysgo.com (David Engraf) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH] i2c: at91: Read all available bytes at once Date: Thu, 26 Apr 2018 07:52:17 +0200 [thread overview] Message-ID: <ddc4beb3-5620-dc69-5b16-bce2737fb59f@sysgo.com> (raw) In-Reply-To: <20180425150853.GU13305@rfolt0960.corp.atmel.com> Hi Ludovic, Am 25.04.2018 um 17:08 schrieb Ludovic Desroches: > 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? I did a quick test by reading RXFL and it worked as well but I decided to use the more readable solution by polling RXRDY. Also I don't need to check if the FIFO has been enabled. If you prefer using RXFL I can create a new patch. Best regards - David > Regards > > Ludovic > >> + } >> >> /* >> * When a NACK condition is detected, the I2C controller sets the NACK, >> -- >> 2.14.1 >> -- Mit freundlichen Gr??en/Best regards, David Engraf Product Engineer SYSGO AG Office Mainz Am Pfaffenstein 14 / D-55270 Klein-Winternheim / Germany Phone: +49-6136-9948-0 / Fax: +49-6136-9948-10 E-mail: david.engraf at sysgo.com _________________________________________________________________________________ Web: https://www.sysgo.com Blog: https://www.sysgo.com/blog Events: https://www.sysgo.com/events Newsletter: https://www.sysgo.com/newsletter _________________________________________________________________________________ Handelsregister/Commercial Registry: HRB Mainz 90 HRB 8066 Vorstand/Executive Board: Etienne Butery (CEO), Kai Sablotny (COO) Aufsichtsratsvorsitzender/Supervisory Board Chairman: Marc Darmon USt-Id-Nr./VAT-Id-No.: DE 149062328
next prev parent reply other threads:[~2018-04-26 5:52 UTC|newest] Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-04-18 12:40 [PATCH] i2c: at91: Read all available bytes at once David Engraf 2018-04-18 12:40 ` David Engraf 2018-04-25 15:08 ` Ludovic Desroches 2018-04-25 15:08 ` Ludovic Desroches 2018-04-25 15:08 ` Ludovic Desroches 2018-04-25 15:43 ` David Engraf 2018-04-25 15:43 ` David Engraf 2018-04-26 8:25 ` Ludovic Desroches 2018-04-26 8:25 ` Ludovic Desroches 2018-04-26 8:25 ` Ludovic Desroches 2018-04-26 9:53 ` [PATCH v2] " David Engraf 2018-04-26 9:53 ` David Engraf 2018-04-26 12:30 ` Ludovic Desroches 2018-04-26 12:30 ` Ludovic Desroches 2018-04-26 12:30 ` Ludovic Desroches 2018-04-28 12:38 ` Wolfram Sang 2018-04-28 12:38 ` Wolfram Sang 2018-04-30 6:11 ` David Engraf 2018-04-30 6:11 ` David Engraf 2018-04-26 5:52 ` David Engraf [this message] 2018-04-26 5:52 ` [PATCH] " David Engraf
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