[U-Boot] [PATCH v1 1/4] arm: socfpga: imply SPL config instead of select

[Dinh Nguyen <dinguyen@kernel.org>]

Hi Simon,

On 1/14/19 9:50 AM, Simon Goldschmidt wrote:
> Am 11.01.2019 um 23:02 schrieb Marek Vasut:
>> On 1/11/19 9:39 PM, Simon Goldschmidt wrote:
>>> Am 07.01.2019 um 23:53 schrieb Marek Vasut:
>>>> On 1/7/19 10:14 PM, Simon Goldschmidt wrote:
>>>>> In order to build a smaller SPL, let's imply SPL_DM_RESET and
>>>>> SPL_WATCHDOG_SUPPORT instead of selecting them, so they can be
>>>>> disabled
>>>>> via defconfig.
>>>>>
>>>>> This also seems to be required to use OF_PLATDATA, as the reset
>>>>> drivers
>>>>> don't seem to work with it.
>>>>
>>>> How do you un-reset IP blocks if you disable the reset controller ?
>>>
>>> I found that out just now: there's the function
>>> 'reset_deassert_peripherals_handoff()' in spl_gen5.c that should
>>> "De-assert reset for peripherals and bridges based on handoff". However,
>>> at least for Gen5, it just writes a 0 to rstmgr->permodrst. By doing
>>> that, it enables *ALL* peripherals on the SoC (except for some DMA
>>> channels that aren't really used) :-)
>>>
>>> I guess that needs some cleaning up as well ;-)
>>
>> Yes
>>
>>> I think the proper thing to do here would be to remove this function and
>>> convert all drivers to provide appropriate 'resets' properties in the
>>> dts?
>>
>> Indeed
> 
> So I just did that and it works nice for SPL and U-Boot: By adding some
> "resets" properties the the main dtsi and adding reset bulk code to the
> cadence_qspi, denali_dt nand and drivers, I can nearly remove the reset
> code from arch/mach_socfpga.
> 
> The problem would be that now Linux cannot use peripherals that aren't
> enabled by U-Boot because it relies on them being enabled. How are such
> dependencies solved? Because even if I would add reset support in the
> corresponding Linux drivers, we probably could not bootolder Kernels
> (e.g. the Debian 9 kernel - v4.9.x) with a new U-Boot...
> 

I added an early reset driver for SoCFPGA that should take care of this.
The patch is in v5.0-rc2[1].

Dinh

[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/reset?id=b3ca9888f35fa6919569cf27c929dc0ac49e9716