linux-kernel - Re: [PATCH v2] serial: sifive: enable clocks for UART when probed

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Message-ID: <mhng-48b61fc8-ae88-4ebe-8d91-b49f13c5ba0f@palmer-ri-x1c9>
Date:   Tue, 20 Sep 2022 13:37:26 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     Olof Johansson <olof@...om.net>
CC:     Greg KH <gregkh@...uxfoundation.org>, jirislaby@...nel.org,
        linux-serial@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Olof Johansson <olof@...om.net>,
        u.kleine-koenig@...gutronix.de, emil.renner.berthing@...onical.com,
        Paul Walmsley <paul.walmsley@...ive.com>
Subject:     Re: [PATCH v2] serial: sifive: enable clocks for UART when probed

On Tue, 20 Sep 2022 09:00:18 PDT (-0700), Olof Johansson wrote:
> When the PWM driver was changed to disable clocks if no PWMs are enabled,
> it ended up also disabling the shared parent with the UART, since the
> UART doesn't do any clock enablement on its own.
>
> To avoid these surprises, switch to clk_get_enabled().
>
> Fixes: ace41d7564e655 ("pwm: sifive: Ensure the clk is enabled exactly once per running PWM")
> Cc: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> Cc: Emil Renner Berthing <emil.renner.berthing@...onical.com>
> Cc: Palmer Dabbelt <palmer@...belt.com>
> Cc: Paul Walmsley <paul.walmsley@...ive.com>
> Signed-off-by: Olof Johansson <olof@...om.net>
>
> ---
>
> v2: Switch to devm_clk_enabled() per Uwe's suggestion.
>
> ---
>  drivers/tty/serial/sifive.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/sifive.c b/drivers/tty/serial/sifive.c
> index 5c3a07546a58..4b1d4fe8458e 100644
> --- a/drivers/tty/serial/sifive.c
> +++ b/drivers/tty/serial/sifive.c
> @@ -945,7 +945,7 @@ static int sifive_serial_probe(struct platform_device *pdev)
>  		return PTR_ERR(base);
>  	}
>
> -	clk = devm_clk_get(&pdev->dev, NULL);
> +	clk = devm_clk_get_enabled(&pdev->dev, NULL);
>  	if (IS_ERR(clk)) {
>  		dev_err(&pdev->dev, "unable to find controller clock\n");
>  		return PTR_ERR(clk);

I have one of these lying around somewhere if you need someone to test 
it, but sounds like you had from the v1 email.  Either way

Acked-by: Palmer Dabbelt <palmer@...osinc.com>
Reviewed-by: Palmer Dabbelt <palmer@...osinc.com>

as this seems better than what was there.

Thanks!