Re: EP93xx PIO IDE driver proposal

["João Ramos" <joao.ramos@inov.pt>]

Alan Cox escreveu:
>> 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?

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?

Best regards,
João


-- 
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    João Ramos        <joao.ramos@inov.pt>

    INOV INESC Inovação - ESTG Leiria
    Escola Superior de Tecnologia e Gestão de Leiria
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    Portugal

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