linux-kernel - Re: [v5 2/2] gpio: aspeed: Add SGPIO driver

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Date:   Mon, 29 Jul 2019 01:37:33 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Hongwei Zhang <hongweiz@....com>
Cc:     Andrew Jeffery <andrew@...id.au>,
        linux-gpio <linux-gpio@...r.kernel.org>,
        Joel Stanley <joel@....id.au>,
        linux-aspeed <linux-aspeed@...ts.ozlabs.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [v5 2/2] gpio: aspeed: Add SGPIO driver

On Mon, Jul 22, 2019 at 10:37 PM Hongwei Zhang <hongweiz@....com> wrote:

> As you suspected it correctly, AST2500 utilizes all the 32 bits of the registers
> (data value, interrupt, etc...), such that using 8-bit bands
> [7:0]/[15:8]/23:16]/[31:24] of GPIO_200H for SGPIO_A/B/C/D .
> so registering 10 gpiochip drivers separately will make code more
> complicated, for example gpio_200 register (data_value reg) has to be
> shared by 4 gpiochip instances, and the same is true for gpio204 (interrupt reg),
> and other more registers.
> So we would prefer to keeping current implementation.

OK this is a pretty good argument. My review assumed one
32-bit register was not shared between banks but it is,
I see.

The above situation can be managed by regmap, but that will
just a different complexity so go with this approach then.

Yours,
Linus Walleij