Discussion about the Linux wbsd driver ()

dezheng shen | 28 Jul 2006 05:37

how to determine the SIZE of SD Host Control Register Map

Dear all:
   We are wondering how to determine the memory size of SD Host Control 
Register Map?

   We found a link here 
http://www.science.unitn.it/~fiorella/guidelinux/tlk/node79.html#SECTION00864100000000000000

   and it explains how to determine the SIZE of a PCI I/O memory space; 
however, our hardware engineer said in PCI spec, it's recommended to 
return 4k as the minimun requirement. In the "sd host controller 
standard specification draft version 1.00 june 2003," the size of "SD 
Host controller register" is 256-byte. So, we are wondering how to 
determine the SIZE of SD Host Control Register Map.

thank you,

dz

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Pierre Ossman | 28 Jul 2006 12:02

Re: how to determine the SIZE of SD Host Control Register Map

dezheng shen wrote:
> Dear all:
>   We are wondering how to determine the memory size of SD Host Control
> Register Map?
>
>   We found a link here
> http://www.science.unitn.it/~fiorella/guidelinux/tlk/node79.html#SECTION00864100000000000000
>
>
>   and it explains how to determine the SIZE of a PCI I/O memory space;
> however, our hardware engineer said in PCI spec, it's recommended to
> return 4k as the minimun requirement. In the "sd host controller
> standard specification draft version 1.00 june 2003," the size of "SD
> Host controller register" is 256-byte. So, we are wondering how to
> determine the SIZE of SD Host Control Register Map.

Well, PCI isn't my field, so I can't really say much about it. All I
know is that the other controllers we've seen (exceed for one odd ball
one), have a I/O area of exactly 256 bytes. All other hardware I've seen
behaves the same way. I would suggest you talk to the maintainer of the
PCI layer in Linux to sort this out. If I'm not mistaken, Greg KH
handles that bit.

Rgds
Pierre

PS. If you already have hardware in production with this problem, we can
always add a quirk for it in the driver. So it's not that big of a
problem in practice.

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dezheng shen | 31 Jul 2006 02:20

Re: how to determine the SIZE of SD Host Control Register Map

    I would suggest you talk to the maintainer of the
> PCI layer in Linux to sort this out. If I'm not mistaken, Greg KH
> handles that bit.

   I will contact this gentleman, thanks.

> 
> Rgds
> Pierre
> 
> PS. If you already have hardware in production with this problem, we can
> always add a quirk for it in the driver. So it's not that big of a
> problem in practice.

   well, we are designing new SD reader hardware and hope the default 
Linux SD can work out of the box. We know it's not difficult to work 
around this bug and our driver can work on DMA mode. We still need to 
run stress test.

thanks,

dz

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