Re: [RFC PATCH] AHCI: Workaround for ATAPI on buggy AHCI controller

[Jeff Garzik <jgarzik@pobox.com>]

On 04/13/2013 01:05 AM, Robert Hancock wrote:
> On 04/12/2013 01:34 PM, Marc C wrote:
>> Hello Jeff,
>>
>> I'm working with a proprietary but AHCI-compatible SATA controller
>> that uses
>> the libata driver. Early versions of this controller have issues with
>> processing
>> non-data ATAPI commands. A workaround was identified which requires some
>> register pokes in the command completion path of the driver. I don't
>> expect to
>> push this patch upstream (yet). However, I would like to get some
>> feedback
>> regarding the workaround, and check if the placement of the code is
>> "acceptable"
>> or if there would be a better place to put it.
>>
>> The workaround itself is rather simple: toggle the START bit
>> immediately after a
>> non-data ATAPI command completes. The ST bit toggle would be performed
>> within
>> atomic context in the AHCI port interrupt ISR.
>>
>> Signed-off-by: Marc C <marc.ceeeee@gmail.com>
>
> This should likely be triggered off a host flag like some of the ones
> already in the driver so it can be done just for the affected
> controllers, not unconditionally.

Indeed -- you don't want to punish the non-buggy 99% case for one weird 
buggy hardware rev.

See AHCI_HFLAG_xxx

	Jeff