[PATCH 3/3] mtd: rawnand: denali: Do not reset the block on SoCFPGA

[Marek Vasut <marex@denx.de>]

On 1/9/20 4:01 PM, Masahiro Yamada wrote:
> On Thu, Jan 9, 2020 at 11:48 PM Marek Vasut <marex@denx.de> wrote:
>>
>> On 1/9/20 1:11 PM, Masahiro Yamada wrote:
>>> On Thu, Jan 9, 2020 at 8:16 PM Marek Vasut <marex@denx.de> wrote:
>>>>
>>>> On 1/9/20 12:04 PM, Masahiro Yamada wrote:
>>>>> On Thu, Jan 9, 2020 at 7:08 PM Marek Vasut <marex@denx.de> wrote:
>>>>>>
>>>>>> Legacy kernel versions for SoCFPGA may not implement proper reset
>>>>>> handling. Apply the same approach as SoCFPGA reset driver, check
>>>>>> environment variable "socfpga_legacy_reset_compat", and if it is
>>>>>> set, do not reset the IP before booting Linux. This way, even the
>>>>>> older kernel versions can be booted by up to date U-Boot.
>>>>>>
>>>>>> Signed-off-by: Marek Vasut <marex@denx.de>
>>>>>> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
>>>>>> ---
>>>>>>  drivers/mtd/nand/raw/denali_dt.c | 12 ++++++++++++
>>>>>>  1 file changed, 12 insertions(+)
>>>>>>
>>>>>> diff --git a/drivers/mtd/nand/raw/denali_dt.c b/drivers/mtd/nand/raw/denali_dt.c
>>>>>> index 2c9e249ab6..d35f2a3543 100644
>>>>>> --- a/drivers/mtd/nand/raw/denali_dt.c
>>>>>> +++ b/drivers/mtd/nand/raw/denali_dt.c
>>>>>> @@ -148,6 +148,18 @@ static int denali_dt_remove(struct udevice *dev)
>>>>>>  {
>>>>>>         struct denali_nand_info *denali = dev_get_priv(dev);
>>>>>>
>>>>>> +#if CONFIG_IS_ENABLED(ARCH_SOCFPGA)
>>>>>> +       /*
>>>>>> +        * Legacy kernel versions do not implement proper reset handling on
>>>>>> +        * SoCFPGA. To let those older kernel versions work, reuse the same
>>>>>> +        * approach as the SoCFPGA reset driver does -- check environment
>>>>>> +        * variable socfpga_legacy_reset_compat and avoid resetting the IP
>>>>>> +        * before booting the kernel if it is set to 1.
>>>>>> +        */
>>>>>> +       if (env_get_ulong("socfpga_legacy_reset_compat", 10, 0))
>>>>>> +               return 0;
>>>>>> +#endif
>>>>>> +
>>>>>>         return reset_release_bulk(&denali->resets);
>>>>>>  }
>>>>>
>>>>>
>>>>> Why don't you simply remove reset_release_bulk() ?
>>>>
>>>> Because once mainline has proper reset handling, this can be used only
>>>> for legacy kernel versions.
>>>
>>>
>>> I am suffering for the same problem for the uniphier platform.
>>
>> The Denali NAND patches for Linux are currently stuck on your review too.
> 
> Huh?
> 
> Which patch in Linux is stuck on my review?

[PATCH V2] mtd: rawnand: denali_dt: Add support for configuring
SPARE_AREA_SKIP_BYTES

>>> The reset driver support for Linux will never be back-ported.
>>> So, it will continue to be a problem for Linux v4.19, v5.4, etc.
>>>
>>> reset_release_bulk() should go away.
>>
>> Once the Linux patches are upstream, we can just reset the NAND
>> controller without problems. And that's the right thing to do, sometimes
>> you don't want NAND to be available in Linux, and then it should be kept
>> in reset.
> 
> 
> The NAND reset in Linux will be available in the future version
> (if my patch is applied).

Which patch ?

> The stable kernels are maintained in 6 years.
> 
> https://www.kernel.org/category/releases.html

How is this relevant ?

> The EOF of Linux 5.4 is set at 2021.12, but
> following the recent rules, it will be extended
> to 2026 or so.

So, for all legacy kernel versions, enable this backward compatibility
thingie.