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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Tue, 10 Mar 2020 10:52:10 +0100
Message-ID: <CAMuHMdUKD5Ob_o4E3bH9wx=6r2PU+7U3RQ_GVRj7ZQc-e5Y4TA@mail.gmail.com>
Subject: Re: [PATCH 1/2] arm64: change ARCH_SPRD Kconfig to tristate
To:     Orson Zhai <orsonzhai@gmail.com>
Cc:     Chunyan Zhang <zhang.lyra@gmail.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>, Jiri Slaby <jslaby@suse.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Chunyan Zhang <chunyan.zhang@unisoc.com>,
        "open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>,
        Baolin Wang <baolin.wang7@gmail.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Android Kernel Team <kernel-team@android.com>
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Hi Orson,

On Tue, Mar 10, 2020 at 10:41 AM Orson Zhai <orsonzhai@gmail.com> wrote:
> On Mon, Mar 9, 2020 at 6:32 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > On Mon, Mar 9, 2020 at 9:32 AM Chunyan Zhang <zhang.lyra@gmail.com> wrote:
> > > On Mon, 9 Mar 2020 at 16:03, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > > > On Thu, Mar 5, 2020 at 11:33 AM Chunyan Zhang <zhang.lyra@gmail.com> wrote:
> > > > > From: Chunyan Zhang <chunyan.zhang@unisoc.com>
> > > > >
> > > > > The default value of Kconfig for almost all sprd drivers are the same with
> > > > > ARCH_SPRD, making these drivers built as modules as default would be easier
> > > > > if we can set ARCH_SPRD as 'm', so this patch change ARCH_SPRD to tristate.
> > > > >
> > > > > Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
> > > >
> > > > Can you actually boot a kernel on a Spreadtrum platform when all platform
> > > > and driver support is modular?
> > >
> > > Yes, even if all drivers are modular.
> >
> > Cool. No hard dependencies on e.g. regulators that are turned off when
> > unused?
> >
> > > But I hope serial can be builtin, then I can have a console to see
> > > kernel output before loading modules.
> >
> > No dependency on the clock driver?
> > Oh, I see you have a hack in the serial driver, to assume default
> > values when the serial port's parent clock is not found.  That may
> > limit use of the other serial ports, depending on the actual serial
> > hardware.
>
> There is an function named "sprd_uart_is_console()" in the driver
> code. So the hack could be only applied when the
> port is identified as console. And other ports might return
> PROBE_DEFER until the clock is ready.
>
> Could it work out of the limitation?

Yes, that could work.  You also have only a single SPRD_DEFAULT_SOURCE_CLK,
which makes it simple to handle.
For other SoCs, there may be a variation of possible values, depending on
SoC and/or board.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds