linux-kernel - Re: [PATCH v4 6/6] gpio: aspeed: Add the flush write to ensure the write complete.

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Message-ID: <CAMRc=MdvV7Z2yPpoR9mXLH6UCF5uA=TbkC_qUSj=akP_09M0WQ@mail.gmail.com>
Date: Wed, 2 Oct 2024 12:27:19 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: Billy Tsai <billy_tsai@...eedtech.com>, robh@...nel.org, krzk+dt@...nel.org, 
	conor+dt@...nel.org, joel@....id.au, andrew@...econstruct.com.au, 
	linux-gpio@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-aspeed@...ts.ozlabs.org, 
	linux-kernel@...r.kernel.org, BMC-SW@...eedtech.com, Peter.Yin@...ntatw.com, 
	Jay_Zhang@...ynn.com
Subject: Re: [PATCH v4 6/6] gpio: aspeed: Add the flush write to ensure the
 write complete.

On Tue, Oct 1, 2024 at 4:18 PM Linus Walleij <linus.walleij@...aro.org> wrote:
>
> On Thu, Sep 19, 2024 at 11:43 AM Billy Tsai <billy_tsai@...eedtech.com> wrote:
>
> > Performing a dummy read ensures that the register write operation is fully
> > completed, mitigating any potential bus delays that could otherwise impact
> > the frequency of bitbang usage. E.g., if the JTAG application uses GPIO to
> > control the JTAG pins (TCK, TMS, TDI, TDO, and TRST), and the application
> > sets the TCK clock to 1 MHz, the GPIO’s high/low transitions will rely on
> > a delay function to ensure the clock frequency does not exceed 1 MHz.
> > However, this can lead to rapid toggling of the GPIO because the write
> > operation is POSTed and does not wait for a bus acknowledgment.
> >
> > Signed-off-by: Billy Tsai <billy_tsai@...eedtech.com>
>
> If this applies cleanly on mainline I think it should go into fixes as-is.
>
> Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
>
> Yours,
> Linus Walleij

I agree but it doesn't. :(

Billy: please send it separately and - while at it - use a C-style comment.

Bart