Re: SATA exceptions with 2.6.20-rc5

Björn Steinbrink wrote:
On 2007.01.21 23:08:11 +0100, Björn Steinbrink wrote:
On 2007.01.21 13:58:01 -0600, Robert Han*** wrote:
Björn Steinbrink wrote:
All kernels were bad using that approach. So back to square 1. :/

Björn

OK guys, here's a new patch to try against 2.6.20-rc5:

Right now when switching between ADMA mode and legacy mode (i.e. when going from doing normal DMA reads/writes to doing a FLUSH CACHE) we just set the ADMA GO register bit appropriately and continue with no delay. It looks like in some cases the controller doesn't respond to this immediately, it takes some nanoseconds for the controller's status registers to reflect the change that was made. It's possible that if we were trying to issue commands during this time, the controller might not react properly. This patch adds some code to wait for the status register to change to the state we asked for before continuing.
I went for the "I feel lucky" route and did just add mmio reads after the
mmio writes, posting them. Rationale being that if it is a write posting
issue, the debug patch would/could actually hide it AFAICT.
It's the "I feel lucky" route, because my whole "knowledge" about mmio
and write posting originates from the few things I read up on when you
discovered the comment about write posting in the generic ata code.

Uhm, yeah, exception occured about the time that I hit "send".

Björn

Yeah, I don't think just adding reads to flush posted writes is enough here - it seems to need more delay than that, and it also wasn't always in the idle state even before we would write the register..

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