linux-kernel - Re: [PATCH v2 3/4] gpio: Add RDA Micro GPIO controller support

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Date:   Mon, 21 Oct 2019 02:57:31 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-unisoc@...ts.infradead.org,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Orson Zhai <orsonzhai@...il.com>
Subject: Re: [PATCH v2 3/4] gpio: Add RDA Micro GPIO controller support

On Sat, Oct 19, 2019 at 6:05 PM Manivannan Sadhasivam
<manivannan.sadhasivam@...aro.org> wrote:
> On Wed, Oct 16, 2019 at 02:41:32PM +0200, Linus Walleij wrote:

> > select GPIO_GENERIC
>
> hmm.. I don't think this driver can use it. Please see the justification
> below.
(...)
> As you can see in this driver, there are 2 separate registers needs to be
> read in order to get the value. RDA_GPIO_VAL needs to be read when the pin
> is in input state and RDA_GPIO_SET needs to be read when the pin is in output
> state.
>
> The MMIO driver relies on a single `dat` register to read the GPIO state and
> this won't fit for this driver and hence my justification for not using it.

Use RDA_GPIO_VAL for dat, then set BGPIOF_READ_OUTPUT_REG_SET
and the mmio core will do what you want I think? That's what the flag is
for IIUC.

Maybe we should document it better :/

Yours,
Linus Walleij