On Thu, Sep 24, 2009 at 01:56:44, Sergei Shtylyov wrote:
> Hello.
>
> Nori, Sekhar wrote:
>
> >>>>> is enabled by proper programming of the IO Expander (TCA6416) ports. 
> >>>>> Also for
> >>>>> RMII PHY to work, the MDIO clock of MII PHY has to be disabled since 
> >>>>> both the
> >>>>> PHYs have the same address. This is done via the GPIO2[6] pin. This 
> >>>>> patch adds
> >>>>> support for RMII PHY.
> >>>>>
> >>>>> This patch also adds a menuconfig option to select UI card and 
> >>>>> peripherals
> >>>>> present on it. Currently, the only sub-option in this menu is RMII.
> >>>>> This menuconfig option is similar to the one present for UI card on
> >>>>> DA830/OMAP-L137 EVM.
> >>>>>
> >>>>> Signed-off-by: Chaithrika U S <[email protected]>
> >>>>>
> >>>>>
> >>>> [...]
> >>>>
> >>>>
> >>>>> diff --git a/arch/arm/mach-davinci/Kconfig 
> >>>>> b/arch/arm/mach-davinci/Kconfig
> >>>>> index 7b6dddf..4ee61cc 100644
> >>>>> --- a/arch/arm/mach-davinci/Kconfig
> >>>>> +++ b/arch/arm/mach-davinci/Kconfig
> >>>>> @@ -129,6 +129,32 @@ config MACH_DAVINCI_DA850_EVM
> >>>>>     help
> >>>>>       Say Y here to select the TI DA850/OMAP-L138 Evaluation Module.
> >>>>>
> >>>>> +config DA850_UI
> >>>>> +   bool "DA850/OMAP-L138 UI (User Interface) board support"
> >>>>> +   depends on MACH_DAVINCI_DA850_EVM
> >>>>> +   help
> >>>>> +     Say Y here if you have the DA850/OMAP-L138 UI
> >>>>> +     (User Interface) board installed and you want to
> >>>>> +     enable the peripherals located on User Interface
> >>>>> +     board.
> >>>>> +
> >>>>> +choice
> >>>>> +   prompt "Select DA850/OMAP-L138 UI board peripheral"
> >>>>> +   depends on DA850_UI
> >>>>>
> >>>>>
> >>>>      Are the devices on the UI board really mutually exclusive?
> >>>>
> >>>>
> >>> What is the purpose of the UI board configuration? Is it just to
> >>> provide one place where all UI board peripherals can be disabled?
> >>>
> >>>
> >>    In case of DA830 EVM, it's a place where the UI board support can be
> >> disabled -- you can't do that with the 'choice' statement which would
> >> alwys select at least one item. But it's not only that. The board has
> >> the GPIO expander which we need not support (and setup) if the board is
> >> absent. It was not clear to me where the TCA6414 GPIO expander is
> >> situated on DA850 EVM -- on the board itself or on the UI daughter board...
> >>
> >
> > On DA830, you can link working on the expander to selection of 
> > NAND/NOR/LCD/MMC
> >
>
>    MMC resides on EVM board itself, while the expander resides on the UI
> board. You only need to touch the expander if the UI board is plugged in.
>
> > MMC/SD is an example where expander operation affects peripherals on
> > baseboard. You want to drive the mux_mode low when MMC/SD is selected.
> >
>
>    Then you can't have neither NAND nor NOR caches. You must select LCD
> in this case. We can add a help text about it.

Irrespective of the help, choosing LCD on UI card to get the MMC/SD on
baseboard working is not intuitive.

> I'd prefer not to add more #ifdef-driven messages as we could use
> da8xx_pinmux_setup()'s ability to return error to check for the PinMux
> reservation conflict.

Pinmux conflict detection is useful and possible on all SoCs, not just
DA8xx. But, as we discussed earlier, not all conflicts are pinmux related.

>
> > I don't see that happening in the current code though.
> >
> > It will be interesting to see if expander access can bail out gracefully
> > if UI card is not connected.
>
>    If I remember correctly (maybe not), there will be error message from
> the I2C driver about a timeout in this case.

Fast expander access bailout will be really useful; I will check it when
I am done with the current patch I am working on.

Thanks,
Sekhar

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