[lkml]   [2014]   [Nov]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] i2c: omap: fix NACK and Arbitration Lost irq handling
On Tue, Nov 18, 2014 at 09:00:58PM +0400, Alexander Kochetkov wrote:
> commit 1d7afc95946487945cc7f5019b41255b72224b70 (i2c: omap: ack IRQ in parts)
> changed the interrupt handler to complete transfers without clearing
> XRDY (AL case) and ARDY (NACK case) flags. XRDY or ARDY interrupts will be
> fired again. As a result, ISR keep processing transfer after it was already
> complete (from the driver code point of view).
> A didn't see real impacts of the 1d7afc9, but it is really bad idea to
> have ISR running on user data after transfer was complete.
> It looks, what 1d7afc9 violate TI specs in what how AL and NACK should be
> handled (see Note 1, sprugn4r, Figure 17-31 and Figure 17-32).
> According to specs (if I understood correctly), in case of NACK and AL driver
> must reset NACK, AL, ARDY, RDR, and RRDY (Master Receive Mode), and
> NACK, AL, ARDY, and XDR (Master Transmitter Mode).
> All that is done down the code under the if condition:
> The patch restore pre 1d7afc9 logic of handling NACK and AL interrupts, so
> no interrupts is fired after ISR informs the rest of driver what transfer
> complete.
> Note: instead of removing break under NACK case, we could just replace 'break'
> with 'continue' and allow NACK transfer to finish using ARDY event. I found
> that NACK and ARDY bits usually set together. That case confirm TI wiki:
> In order if someone interested in the event traces for NACK and AL cases,
> I sent them to mailing list.
> Tested on Beagleboard XM C.
> Signed-off-by: Alexander Kochetkov <>
> Fixes: 1d7afc9 i2c: omap: ack IRQ in parts
> Cc: <> # v3.7+

Applied to for-current, thanks!

[unhandled content-type:application/pgp-signature]
 \ /
  Last update: 2014-11-21 08:21    [W:0.069 / U:1.996 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site