[PATCH v8 4/9] davinci: McASP configuration for Omapl138-Hawkboard

[Nori, Sekhar]

Hi Michael,

On Wed, Nov 17, 2010 at 02:12:53, Michael Williamson wrote:
>
> Help me out.  Why do we need generic pin lists?
>

They might help in cases where all boards will use the same set of
pins. For example, every one who uses I2C will most likely both the
clock and data pins from the IP. For more complex peripherals with
different pins options they serve a documentation purpose at best.

> It seems to me that the "generic pin list" for da850.c isn't practical for most
> (if not all) of the peripherals.  They should be done using __initdata in
> each board file.

Yes, agreed.

>
> Just a cursory glance at what's in da850.c highlights several items being set
> up for the EVM and not generically.  For example:
>
> - da850_uart1_pins and da850_uart2_pins: I believe both have RTS/CTS pins which
>   for a generic definition should be included as for UART0, but would then
>   be unused as the EVM doesn't use these pins in this function.

Yes, the generic pin list should have RTS and CTS pins defined for UART1
and UART2. This needs fixing.

>
> - da850_mcasp_pins: if generic, must include all 16 AXR pins.  I think you'd
>   be hard pressed to find a board configuration that would use all 16 AXR pins
>   for the McASP.  I'm fairly sure the EVM uses the pins called out, and uses
>   other pins for other functions.  So it's likely this structure wouldn't get used.

Yes, the generic pin list should either be completed or removed
altogether and the existing pin list da850_mcasp_pins should be
copied into the board file and called da850_evm_mcasp_pins.

>
> - da850_mmcsd0_pins : includes 2 GPIO pins (specific to the EVM, though possible for
>   other boards) for the card detect and write protect signals.  These pins are
>   completely arbitrary for that particular board design. I also believe that
>   the complete mmcsd0 port has 4 more data lines as part of it's peripheral, although
>   the driver doesn't support using them.

This is incorrect again. The generic pin list should be completed
(or removed) and the existing list should be copied into the EVM board
file as da850_evm_mmcsd0_pins.

>
> - da850_emif25_pins interface doesn't include the generic pins for some of
>   the SDRAM functions.

Yes, this should be completed (or removed). This list is unused anyway.

>
> - da850_cpgmac_pins defines both RMII and MII pins.  I don't think any board
>   would want to configure both sets at the same time.  Seems like this should
>   never get used...

Agreed.

>
> It's also incomplete.  What about the uPP pin list?  Or the VPIF?  Etc.

These should be added as the drivers for these devices are
supported.

>
> I think a board file author should be familiar enough with the SoC to understand
> what peripheral pins he should be configuring for his/her particular hardware setup
> and explicitly specify them in the board file.

Agree.

>
> If you remove the common pin-mux lists and move them to a board file, then once you
> configure your specific platform, is there any more memory used than with
> the common scheme?  Of course, there would be replication of pin-mux code in the board

There is no memory wastage. All the pin lists are init data.

I too prefer all generic pin lists which are most likely not
going to be used at all to be removed. Unused stuff like this
will only make code difficult to read.

Thanks,
Sekhar