Re: [PATCH ide] : Increase WAIT_DRQ to support slow CF cards

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Hello.

Philippe De Muyter wrote:

>> From: Robert Hancock <hancockrwd@gmail.com>
>> Date: Mon, 26 Oct 2009 19:40:03 -0600
>>
>>     
>>> On Mon, Oct 26, 2009 at 7:19 PM, David Miller <davem@davemloft.net> wrote:
>>>       
>>>> Meanwhile we should provide a way for things to work, and
>>>> realistically the only way to do that currently is to bump the
>>>> WAIT_DRQ value to some large number.
>>>>
>>>> And that's exactly the kind of patch I'm willing to accept for this.
>>>>         
>>> I agree, it's sub-optimal but it helps.. if the user wants better
>>> behavior they should a) fix it so that the card isn't using PIO, at
>>> least if it supports DMA and b) not use drivers/ide..
>>>       
>
> Strangely enough, I also had no timeout problem if I started my kernel with
> 'ide=nodma', instead of increasing WAIT_DRQ.

    Hm, interesting...

>  So I surmise that WAIT_DRQ is used in the dma case.
>
>   

   It's used only for the PIO write commands -- see do_rw_taskfile() in 
ide-taskfile.c... DMA commands don't require waiting for BSY=0, DRQ=1 
condition.

> Philippe
>   

WBR, Sergei