Re: [RFC PATH 2/2] gpio: starfive-jh7100: Add StarFive JH7100 GPIO driver

From: Michael Walle <michael@walle.cc>
To: Drew Fustini <drew@beagleboard.org>
Cc: Rob Herring <robh+dt@kernel.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	Bartosz Golaszewski <bgolaszewski@baylibre.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Michael Zhu <michael.zhu@starfivetech.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Fu Wei <tekkamanninja@gmail.com>,
	linux-kernel@vger.kernel.org, linux-gpio@vger.kernel.org,
	linux-riscv@lists.infradead.org, devicetree@vger.kernel.org,
	Emil Renner Berthing <kernel@esmil.dk>,
	Huan Feng <huan.feng@starfivetech.com>
Subject: Re: [RFC PATH 2/2] gpio: starfive-jh7100: Add StarFive JH7100 GPIO driver
Date: Fri, 02 Jul 2021 16:59:51 +0200	[thread overview]
Message-ID: <c915172ac456b3f7b7547c065c41750b@walle.cc> (raw)
In-Reply-To: <20210701203333.GA963857@x1>

Hi Drew,

Am 2021-07-01 22:33, schrieb Drew Fustini:
> On Thu, Jul 01, 2021 at 08:39:40AM +0200, Michael Walle wrote:
>> Hi Drew,
>> 
>> Am 2021-07-01 02:20, schrieb Drew Fustini:
>> > Add GPIO driver for the StarFive JH7100 SoC [1] used on the
>> > BeagleV Starlight JH7100 board [2].
>> >
>> > [1] https://github.com/starfive-tech/beaglev_doc/
>> > [2] https://github.com/beagleboard/beaglev-starlight
>> >
>> > Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
>> > Signed-off-by: Huan Feng <huan.feng@starfivetech.com>
>> > Signed-off-by: Drew Fustini <drew@beagleboard.org>
>> 
>> Could this driver use GPIO_REGMAP and REGMAP_IRQ? See
>> drivers/gpio/gpio-sl28cpld.c for an example.
>> 
>> -michael
> 
> Thank you for the suggestion.  I am not familiar with GPIO_REGMAP and
> REGMAP_IRQ so I will read about it.  Is the advantage is that is helps
> to reduce code duplication by using an abstraction?

Yes, I've looked briefly at your patch and it seemed that GPIO_REGMAP
might fit here which will reduce code.

> I did notice that the gpio-sifive.c driver used regmap_update_bits() 
> and
> regmap_write().
> 
> I suppose that is better than writel_relaxed() and iowrite32() which
> this RFC driver does?

Its just another abstraction layer in between. For MMIO it will also
end up using some variant of the above (see regmap-mmio.c). But if you
use regmap, you can also use REGMAP_IRQ which might also be a fit
for your GPIO controller and thus don't have to implement your own
versions for the irq_chip ops.

-michael

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