Re: EP93xx PIO IDE driver proposal

[Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>]

On Friday 08 May 2009 20:16:56 João Ramos wrote:
> Bartlomiej Zolnierkiewicz escreveu:
> > On Friday 08 May 2009 19:28:22 João Ramos wrote:
> >   
> >>> 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 after all this discussion ;-) , my driver will have no 'init_hwif' 
> >> method, and the setup code will be on 'ep93xx_ide_probe', which will 
> >> configure entirely the IDE host controller.
> >> Moreover, this initial configuration will setup the controller to work 
> >> at PIO Mode 0. Later on, the 'set_pio_mode' method will be called and 
> >> the controller will configure itself according to the PIO mode reported 
> >> by the IDE core.
> >>
> >> Can I proceed this way?
> >>     
> >
> > Well, yes.  Though I hoped that you would at least give a try to fixing
> > IDE core to program PIO0 initially for all host drivers that implement
> > ->set_pio_mode method...
> >   
> 
> Sorry, I didn't noticed your hint... Sure, I can give it a try ;-)
> Maybe with a little help, but I can try. You mean, when the host driver 
> is registered (ide_host_register, or ide_host_add that later calls 
> ide_host_register), maybe in the 'ide_init_port' method (sorry, I need 
> some guidance here...) check if the 'set_pio_mode' method is 
> implemented, and after initializing each port (d->init_hwif(hwif)) 
> default it to PIO Mode 0, calling set_pio_mode method.

ide_init_port() seems OK but I think that ide_port_init_devices()
[it is called after ide_init_port()] would be a bit safer and more
flexible (some host drivers may also require special ->init_dev
setup first) and the check for ->set_pio_mode method presence can
be done just before actually using the method, i.e.

	const struct ide_port_ops *port_ops = hwif->port_ops;

	if (port_ops && port_ops->set_pio_mode)
		port_ops->set_pio_mode(...)

> Is this correct? Sorry, has I stated earlier, I'm wasn't familiar with 
> the IDE susbsystem untill I wrote this patch; but I'm willing to 
> contribute in any way I can, so please, bear with me on this :-) .

Sure, nobody starts from the expert level and not all maintainers are
into "prove the maintainer wrong" elitist's idiocy. ;)

> >   
> >>>   
> >>>       
> >>>> There's just only one issue; normally, I would setup the specific 
> >>>> timings (t0, t1, t2, t2i, etc) in the 'pio_set_mode' hook. However, if 
> >>>> you look further in the driver, those timings aren't defined through a 
> >>>> memory controller but instead manually enforced by 'ndelay' calls (arghhh).
> >>>> This means that in my low-level procedures for reading and writing, I 
> >>>> need to have access to the timings (or the struct ide_timing) 
> >>>> corresponding to the PIO mode selected, in order to use the correct delays.
> >>>>
> >>>> My question is: which is the best way to accomplish this? Declaring a 
> >>>> global struct ide_timing variable pointer that always holds the correct 
> >>>> ide_timing struct to the selected PIO mode? Or should I always check (in 
> >>>> some manner) what is the current PIO mode and then select the adequate 
> >>>> delays?
> >>>>     
> >>>>         
> >>> I think that the setting variable pointer in ->set_pio_mode method would
> >>> work best.  Seems like the existing drive_data field of ide_drive_t is well
> >>> suited for this purpose (however it may be worth to convert it to 'void *'
> >>> type while we are it).
> >>>   
> >>>       
> >> Did you mean 'drive_data' field, or 'driver_data' field?
> >> 'drive_data' field is an unsigned int value; I guess you meant 
> >> 'driver_data' field as it is a (void *) field, so I can define it as a 
> >> pointer to the correct 'struct ide_timing'.
> >>     
> >
> > That is why I hinted that you may need to convert 'drive_data' to
> > 'void *' type first.  You may also try to use 'driver_data' instead
> > but you will discover rather quickly that you shouldn't do this... ;)
> >
> > 'driver_data' is for use by IDE core and IDE device drivers.
> >
> > 'drive_data' is for use by IDE host drivers.
> >   
> 
> And this conversion is made by my driver code, or should I fix directly 
> in the ide_drive_t structure?

The latter -- ide_drive_t is the place needing fixing.

Thanks,
Bart