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

[Marek Vasut]

On 1/14/19 5:05 PM, Simon Goldschmidt wrote:
> Hi Dinh,

Hi,

> Am 14.01.2019 um 16:58 schrieb Dinh Nguyen:
>> 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].
> 
> OK, it's good to know that this work is already done, I haven't
> monitored this close enough.

We had the same problem with A10, indeed.

> But am I correct that my above problem remains even in v5.0 as not all
> peripherals in socfpga.dtsi have a "resets" property set (e.g. mmc and
> qspi) and would thuse not be taken out of reset by Linux?
> 
> Plus: should U-Boot work with older Linux kernels? Because if so, we
> need fallback code in U-Boot to unreset peripherals when running with an
> older kernel...

Yes, it'd break old broken kernels . The real question is, do we care ?

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


-- 
Best regards,
Marek Vasut