linux-kernel - Re: [PATCH] irqchip: Replace update_bits with write

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Date:   Wed, 24 Nov 2021 09:50:01 +0000
From:   Joel Stanley <joel@....id.au>
To:     Billy Tsai <billy_tsai@...eedtech.com>
Cc:     Eddie James <eajames@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Andrew Jeffery <andrew@...id.au>,
        linux-aspeed <linux-aspeed@...ts.ozlabs.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        BMC-SW <BMC-SW@...eedtech.com>
Subject: Re: [PATCH] irqchip: Replace update_bits with write_bits.

On Wed, 24 Nov 2021 at 09:43, Billy Tsai <billy_tsai@...eedtech.com> wrote:
>
> The interrupt status bits are cleared by writing 1, we should force a
> write to clear the interrupt without checking if the value has changed.
>
> Fixes: 04f605906ff0 ("irqchip: Add Aspeed SCU interrupt controller")
> Signed-off-by: Billy Tsai <billy_tsai@...eedtech.com>

Good catch. This should go to stable too.

Reviewed-by: Joel Stanley <joel@....id.au>

Is there any reason to use the regmap abstraction in this driver?
AFAICT the registers aren't shared, so we could replace the regmap
calls with readl/writel. Such a cleanup probably wouldn't be
backported, so this patch is still useful.

> ---
>  drivers/irqchip/irq-aspeed-scu-ic.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/irqchip/irq-aspeed-scu-ic.c b/drivers/irqchip/irq-aspeed-scu-ic.c
> index f3c6855a4cef..18b77c3e6db4 100644
> --- a/drivers/irqchip/irq-aspeed-scu-ic.c
> +++ b/drivers/irqchip/irq-aspeed-scu-ic.c
> @@ -76,8 +76,8 @@ static void aspeed_scu_ic_irq_handler(struct irq_desc *desc)
>                 generic_handle_domain_irq(scu_ic->irq_domain,
>                                           bit - scu_ic->irq_shift);
>
> -               regmap_update_bits(scu_ic->scu, scu_ic->reg, mask,
> -                                  BIT(bit + ASPEED_SCU_IC_STATUS_SHIFT));
> +               regmap_write_bits(scu_ic->scu, scu_ic->reg, mask,
> +                                 BIT(bit + ASPEED_SCU_IC_STATUS_SHIFT));
>         }
>
>         chained_irq_exit(chip, desc);
> --
> 2.25.1
>