Re: [RFC PATCH V4 6/6] riscv: soc: Add Allwinner SoC kconfig option

[Randy Dunlap <rdunlap@infradead.org>]

On 9/13/21 10:16 PM, Anup Patel wrote:
> On Tue, Sep 14, 2021 at 8:36 AM Randy Dunlap <rdunlap@infradead.org> wrote:
>>
>> On 9/13/21 7:34 PM, Guo Ren wrote:
>>> On Tue, Sep 14, 2021 at 2:49 AM Randy Dunlap <rdunlap@infradead.org> wrote:
>>>>
>>>> On 9/13/21 2:20 AM, Guo Ren wrote:
>>>>> On Mon, Sep 13, 2021 at 4:45 PM Maxime Ripard <maxime@cerno.tech> wrote:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> On Sat, Sep 11, 2021 at 05:21:39PM +0800, guoren@kernel.org wrote:
>>>>>>> From: Liu Shaohua <liush@allwinnertech.com>
>>>>>>>
>>>>>>> Add Allwinner kconfig option which selects SoC specific and common
>>>>>>> drivers that is required for this SoC.
>>>>>>>
>>>>>>> Allwinner D1 uses custom PTE attributes to solve non-coherency SOC
>>>>>>> interconnect issues for dma synchronization, so we set the default
>>>>>>> value when SOC_SUNXI selected.
>>>>>>>
>>>>>>> Signed-off-by: Liu Shaohua <liush@allwinnertech.com>
>>>>>>> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
>>>>>>> Signed-off-by: Wei Fu <wefu@redhat.com>
>>>>>>> Cc: Anup Patel <anup.patel@wdc.com>
>>>>>>> Cc: Atish Patra <atish.patra@wdc.com>
>>>>>>> Cc: Christoph Hellwig <hch@lst.de>
>>>>>>> Cc: Chen-Yu Tsai <wens@csie.org>
>>>>>>> Cc: Drew Fustini <drew@beagleboard.org>
>>>>>>> Cc: Maxime Ripard <maxime@cerno.tech>
>>>>>>> Cc: Palmer Dabbelt <palmerdabbelt@google.com>
>>>>>>> Cc: Wei Wu <lazyparser@gmail.com>
>>>>>>> ---
>>>>>>>     arch/riscv/Kconfig.socs      | 15 +++++++++++++++
>>>>>>>     arch/riscv/configs/defconfig |  1 +
>>>>>>>     2 files changed, 16 insertions(+)
>>>>>>>
>>>>>>> diff --git a/arch/riscv/Kconfig.socs b/arch/riscv/Kconfig.socs
>>>>>>> index 30676ebb16eb..8721c000ef23 100644
>>>>>>> --- a/arch/riscv/Kconfig.socs
>>>>>>> +++ b/arch/riscv/Kconfig.socs
>>>>>>> @@ -70,4 +70,19 @@ config SOC_CANAAN_K210_DTB_SOURCE
>>>>>>>
>>>>>>>     endif
>>>>>>>
>>>>>>> +config SOC_SUNXI
>>>>>>> +     bool "Allwinner SoCs"
>>>>>>> +     depends on MMU
>>>>>>> +     select DWMAC_GENERIC
>>>>>>> +     select ERRATA_THEAD
>>>>>>> +     select RISCV_DMA_NONCOHERENT
>>>>>>> +     select RISCV_ERRATA_ALTERNATIVE
>>>>>>> +     select SERIAL_8250
>>>>>>> +     select SERIAL_8250_CONSOLE
>>>>>>> +     select SERIAL_8250_DW
>>>>>>> +     select SIFIVE_PLIC
>>>>>>> +     select STMMAC_ETH
>>>>>>> +     help
>>>>>>> +       This enables support for Allwinner SoC platforms like the D1.
>>>>>>> +
>>>>>>
>>>>>> I'm not sure we should select the drivers there. We could very well
>>>>>> imagine a board without UART, or even more so without ethernet.
>>>>> We just want people could bring D1 up easier, 8250 is the basic component.
>>>>>
>>>>>
>>>>>>
>>>>>> These options should be in the defconfig.
>>>>
>>>> Agreed, using a defconfig is the right way to do this.
>>> Put 8250 related configs into arch/riscv/configs/defconfig?
>>>
>>>    @Palmer Dabbelt @Arnd Bergmann, How do you think about that?
>>> (defconfig or Kconfig.soc)
>>> My purpose is when people make the Image from riscv/defconfig, then
>>> the Image could run on all platforms include D1.
>>
>> Hi,
>>
>> I certainly did not understand your purpose with the patch being
>> able to build a kernel that would run on multiple platforms.
>> Still, I would not expect to see one platform cause unnecessary
>> drivers to be built for platforms that don't need them.
>>
>> Kconfig.socs in arch/riscv/ is a bit of an unusual Kconfig file
>> IMO -- I suppose what you want to do fits into its style.
>>
>> AFAIK the suggestion to use a defconfig (at least my suggestion)
>> was expecting to have a defconfig for each platform, but that
>> would not give you a boot image that could run on all platforms.
> 
> AFAIK, having a separate defconfig for each platform is not going
> to fly with distros (AFAIK). We can't expect dirstros to release
> separate RISC-V kernel image for each platform. In fact, ARM64
> kernel has just one defconfig whereas ARM32 kernel has
> consolidated and minimized number of defconfigs.
> 
> The long term goal for Linux RISC-V is to support single kernel
> image booting on multiple-platforms. Of course, users can always
> strip down the kernel using their custom defconfigs.

OK, thanks for the info.

-- 
~Randy