linux-kernel - Re: [PATCH] mfd: altera-sysmgr: enable raw spinlock feature for preempt-rt kernel

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Date:   Tue, 16 Nov 2021 13:02:18 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Meng Li <Meng.Li@...driver.com>
Cc:     thor.thayer@...ux.intel.com, Lee Jones <lee.jones@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mfd: altera-sysmgr: enable raw spinlock feature for
 preempt-rt kernel

On Tue, Nov 16, 2021 at 11:54 AM Meng Li <Meng.Li@...driver.com> wrote:
> diff --git a/drivers/mfd/altera-sysmgr.c b/drivers/mfd/altera-sysmgr.c
> index 5d3715a28b28..27271cec5d53 100644
> --- a/drivers/mfd/altera-sysmgr.c
> +++ b/drivers/mfd/altera-sysmgr.c
> @@ -83,6 +83,9 @@ static struct regmap_config altr_sysmgr_regmap_cfg = {
>         .fast_io = true,
>         .use_single_read = true,
>         .use_single_write = true,
> +#ifdef CONFIG_PREEMPT_RT
> +       .use_raw_spinlock = true,
> +#endif

I think you should remove the #ifdef here: if PREEMPT_RT is disabled, the flag
has no effect because spinlock behaves the same way as raw_spinlock. If
anything else starts requiring the use of raw spinlocks, then we probably
want the flag to be set  here as well.

       Arnd