Re: EP93xx PIO IDE driver proposal

["João Ramos" <joao.ramos@inov.pt>]

Bartlomiej Zolnierkiewicz escreveu:
> On Thursday 07 May 2009 17:33:20 João Ramos wrote:
>   
>> 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?
>>     
>
> 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?

>   
>> 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).
>   

Ok, so I will set an struct ide_timing pointer in the 'set_pio_mode' 
method, which will later be used by my low-level read/write procedures 
to check the adequate IDE timings.

> Thanks,
> Bart
>
>   

Best regards,
João Ramos


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

    INOV INESC Inovação - ESTG Leiria
    Escola Superior de Tecnologia e Gestão de Leiria
    Edíficio C1, Campus 2
    Morro do Lena, Alto do Vieiro
    Leiria
    2411-901 Leiria
    Portugal

    Tel: +351244843424
    Fax: +351244843424

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