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

[Sergei Shtylyov]

Hello.

Philippe De Muyter wrote:

> > From: Robert Hancock <hancockrwd@xxxxxxxxx>
> > Date: Mon, 26 Oct 2009 19:40:03 -0600
> >
> >     
> > > On Mon, Oct 26, 2009 at 7:19 PM, David Miller <davem@xxxxxxxxxxxxx> 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


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