linux-kernel - Re: [PATCH v4 02/17] clk: at91: pmc: execute suspend/resume only for backup mode

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Date:   Thu, 07 Oct 2021 20:51:36 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Claudiu Beznea <claudiu.beznea@...rochip.com>,
        alexandre.belloni@...tlin.com, ludovic.desroches@...rochip.com,
        mturquette@...libre.com, nicolas.ferre@...rochip.com
Cc:     linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        Claudiu Beznea <claudiu.beznea@...rochip.com>
Subject: Re: [PATCH v4 02/17] clk: at91: pmc: execute suspend/resume only for backup mode

Quoting Claudiu Beznea (2021-09-23 06:20:31)
> Before going to backup mode architecture specific PM code sets the first
> word in securam (file arch/arm/mach-at91/pm.c, function at91_pm_begin()).
> Thus take this into account when suspending/resuming clocks. This will
> avoid executing unnecessary instructions when suspending to non backup
> modes. Also this commit changed the postcore_initcall() with
> subsys_initcall() to be able to execute of_find_compatible_node() since
> this was not available at the moment of postcore_initcall(). This should
> not alter the tcb_clksrc since the changes are related to clocks
> suspend/resume procedure that will be executed at the user space request,
> thus long ago after subsys_initcall().

Is the comment still relevant though?

> 
> Signed-off-by: Claudiu Beznea <claudiu.beznea@...rochip.com>
> ---
> diff --git a/drivers/clk/at91/pmc.c b/drivers/clk/at91/pmc.c
> index b2806946a77a..58e9c088cb22 100644
> --- a/drivers/clk/at91/pmc.c
> +++ b/drivers/clk/at91/pmc.c
> @@ -110,13 +112,35 @@ struct pmc_data *pmc_data_allocate(unsigned int ncore, unsigned int nsystem,
>  }
>  
>  #ifdef CONFIG_PM
> +
> +/* Address in SECURAM that say if we suspend to backup mode. */
> +static void __iomem *at91_pmc_backup_suspend;
> +
>  static int at91_pmc_suspend(void)
>  {
> +       unsigned int backup;
> +
> +       if (!at91_pmc_backup_suspend)
> +               return 0;
> +
> +       backup = *(unsigned int *)at91_pmc_backup_suspend;

This will fail sparse. Why are we reading iomem without using iomem
reading wrapper?

> +       if (!backup)