Re: EP93xx PIO IDE driver proposal

[Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>]

On Friday 08 May 2009 15:30:00 Sergei Shtylyov wrote:
> Bartlomiej Zolnierkiewicz wrote:
> 
> >>>>>>So you're saying I should support all PIO modes? If so, I would have to 
> >>>>>>make conditional code, checking perhaps a module param to sort which PIO 
> >>>>>>mode to use.
> 
> >>>>>If you advertise PIO0-PIO4 as supported the core IDE code will do all the
> >>>>>work on figuring which modes are supported by the attached devices. You
> >>>>>just need to be able to set them.
> 
> >>>>>Alan
> 
> >>>>Ok, so I've been studying that (I was quite lost for a time, I confess, 
> >>>>I'm not that much familiar with the IDE subsystem, so please bear with 
> >>>>me ;-) ).
> 
> >>>>So I need to set up a hook for 'set_pio_mode()', so that when the IDE 
> >>>>subsystem detects a device and figures the most suitable PIO mode for 
> >>>>the device, it will call the 'set_pio_mode' routine provided by the 
> >>>>driver in order to configure the host controller for that PIO mode.
> 
> >>>>This also means that my host controller driver should always default to 
> >>>>PIO Mode 0, as the initial host controller setup that is carried out by 
> >>>>the 'init_hwif' routine, allowing devices to be detected. Afterwards, 
> >>>>the IDE subsystem detects the most suitable PIO mode and calls 
> >>>>'set_pio_mode' to change that configuration.
> 
> >>>>Am I correct on this?
> 
> >>>Yes! :)
> 
> >>>There is still a room for improvement though -- it would be better to fix
> >>>IDE core to set PIO0 before probing devices for all host controllers.
> 
> >>>Moreover it seems that doing it this way would allow us to remove ->init_hwif
> >>>method from this driver and do all necessary setup in ep93xx_ide_probe()
> >>>(this controller is a single port one so theoretically there shouldn't be
> >>>a need for having per-port ->init_hwif implementation).
> 
> >>So, I should remove the 'init_hwif' hook, and all the host controller 
> >>setup would be made in the driver's probe method, correct?
> 
> > Yes, that would be preferred (of course given that you fix IDE core to do
> > initial PIO0 setup first).
> 
>     Er, it's not that easy... Think about older CompactFlash cards (and 
> ancient drives of course) that don't support setting explicit PIO modes 
> (only the default one) since they don't support IORDY... and also 
> ide_config_drive_speed() expects drive->id to be already filled in... So I 
> guess you mean just calling set_pio_mode() prior to probing -- without 
> setting the drive's own mode?

Yes, I mean setting PIO0 _only_ on host.

Thanks,
Bart