Re: [PATCH 2/2] ARM: OMAP2: Fix GPMC memory initialisation

[Jon Hunter <jon-hunter@ti.com>]

On 02/04/2013 01:15 PM, Tony Lindgren wrote:
> * Jon Hunter <jon-hunter@ti.com> [130204 10:49]:
>> On 02/04/2013 11:45 AM, Tony Lindgren wrote:
>>>
>>> AFAIK SYSBOOT_n values reflect the boot time values of the actual SYSBOOT
>>> pins, so using generic pinconf there makes sense. But this of course should
>>> be checked.
>>
>> Not sure I am a fan of that idea. It is possible the pins could be
>> re-used as GPIOs after reset. Given that the state at reset is latched
>> in a register, it is best just to read the register directly.
> 
> Yes the physical SYSBOOT pins can be reused as GPIO, but that's are already
> handled by the padconf and GPIO registers. This is a different register
> showing the boot time pin values for some pins. So it makes sense to use
> generic pinconf to make the pin values available to the client drivers
> as needed.
> 
> The advantage doing it this way is that we don't need to export any omap
> custom functions to the drivers from the SCM driver. This way we need zero
> platform glue code, and can deal with it directly in the drivers in a
> generic way. And all we need to do is just need to map the SoC specific
> SYSBOOT pin register in the .dts files.

I see what you are saying exporting the state in control_status register
via the pinconf. That could work.

> It may also make sense to export DEVICETYPE this way. At least early omaps
> had the GP vs HS mode configured by pulls on some pins during the boot time.
> So those bits too may reflect actual physical pins during the boot time
> configured by the efuse settings?

I *believe* that was only omap1.

>>>>> Regarding omap_device, we should find a way to keep the dependencies
>>>>> between drivers and the bus code down to minimum. So ideally things
>>>>> like this would be only done using just the compatible flag. But the
>>>>> pdata we cannot remove quite yet.
>>>>
>>>> Agree. However, there are several drivers today (gpio, dmtimer, mmc,
>>>> serial, dss, etc), that make use of a function pointer to
>>>> omap_pm_get_dev_context_loss_count() to determine when the peripheral's
>>>> state has been lost. When booting with DT this function pointer is not
>>>> populated and so with DT we currently have no way to determine this. I
>>>> see this as a blocker to migrating completely to DT. Ideally we would
>>>> find a way for RPM to handle this and remove the function pointer.
>>>> However, right now we still need a generic way to pass this type of
>>>> platform data to drivers.
>>>
>>> Yeah pinconf generic won't help us with the legacy boot.
>>
>> Right. I view all this sort of thing as system-level device information
>> that some drivers may need. It does not seem that we have a good way to
>> handle that at the moment. Any ideas?
> 
> I suggest just passing it in in pdata for now for the legacy boot. Then
> I suggest we make what we can generic with pinconf in the long run.

I don't see why we would want to export a function pointer to
omap_pm_get_dev_context_loss_count() with pinconf. Have we got our wires
crossed here?

Jon