From: David Engraf Date: Thu, 26 Apr 2018 09:53:14 +0000 (+0200) Subject: i2c: at91: Read all available bytes at once X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=e8f39e9fc0e0b7bce24922da925af820bacb8ef8;p=linux.git i2c: at91: Read all available bytes at once 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 [wsa: reformatted comment] Signed-off-by: Wolfram Sang --- diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c index bfd1fdff64a97..3f3e8b3bf5ff9 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,