Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1253795

Re: [PATCH v2 1/2] i2c: at91: fix write transfers by clearing pending interrupt first

Show all headers | View raw

[Multipart message — attachments visible in raw view] - view raw

On Wed, Oct 21, 2015 at 03:44:03PM +0200, Ludovic Desroches wrote:
> From: Cyrille Pitchen <cyrille.pitchen@atmel.com>
> 
> In some cases a NACK interrupt may be pending in the Status Register (SR)
> as a result of a previous transfer. However at91_do_twi_transfer() did not
> read the SR to clear pending interruptions before starting a new transfer.
> Hence a NACK interrupt rose as soon as it was enabled again at the I2C
> controller level, resulting in a wrong sequence of operations and strange
> patterns of behaviour on the I2C bus, such as a clock stretch followed by
> a restart of the transfer.
> 
> This first issue occurred with both DMA and PIO write transfers.
> 
> Also when a NACK error was detected during a PIO write transfer, the
> interrupt handler used to wrongly start a new transfer by writing into the
> Transmit Holding Register (THR). Then the I2C slave was likely to reply
> with a second NACK.
> 
> This second issue is fixed in atmel_twi_interrupt() by handling the TXRDY
> status bit only if both the TXCOMP and NACK status bits are cleared.
> 
> Tested with a at24 eeprom on sama5d36ek board running a linux-4.1-at91
> kernel image. Adapted to linux-next.
> 
> Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
> Fixes: 93563a6a71bb ("i2c: at91: fix a race condition when using the DMA controller")
> Reported-by: Peter Rosin <peda@lysator.liu.se>
> Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
> Tested-by: Peter Rosin <peda@lysator.liu.se>
> Cc: stable@vger.kernel.org #4.1

Applied to for-next, thanks!

I considered for-current, but really want this to sit a little in
for-next to make sure there are no regressions. It will go back via
stable.

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

[PATCH v2 1/2] i2c: at91: fix write transfers by clearing pending interrupt first Ludovic Desroches <ludovic.desroches@atmel.com> - 2015-10-21 15:50 +0200
  [PATCH v2 2/2] i2c: at91: manage unexpected RXRDY flag when starting a transfer Ludovic Desroches <ludovic.desroches@atmel.com> - 2015-10-21 15:50 +0200
    Re: [PATCH v2 2/2] i2c: at91: manage unexpected RXRDY flag when  starting a transfer Wolfram Sang <wsa@the-dreams.de> - 2015-10-22 15:10 +0200
      [PATCH v3] i2c: at91: manage unexpected RXRDY flag when starting a transfer Ludovic Desroches <ludovic.desroches@atmel.com> - 2015-10-26 10:40 +0100
        Re: [PATCH v3] i2c: at91: manage unexpected RXRDY flag when starting  a transfer Wolfram Sang <wsa@the-dreams.de> - 2015-10-26 15:50 +0100
  Re: [PATCH v2 1/2] i2c: at91: fix write transfers by clearing  pending interrupt first Wolfram Sang <wsa@the-dreams.de> - 2015-10-22 15:10 +0200

csiph-web