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

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Date:   Fri, 08 Oct 2021 15:05:17 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Claudiu.Beznea@...rochip.com, Ludovic.Desroches@...rochip.com,
        Nicolas.Ferre@...rochip.com, alexandre.belloni@...tlin.com,
        mturquette@...libre.com
Cc:     linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 02/17] clk: at91: pmc: execute suspend/resume only for backup mode

Quoting Claudiu.Beznea@...rochip.com (2021-10-07 23:47:14)
> On 08.10.2021 06:51, Stephen Boyd wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > 
> > 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?
> 
> For architecture PM code yes, the securam is set in [1].
> 
> Related to replacing postcore_init() with subsys_initcall() to be able to
> have the proper result of of_find_compatible_node() I have to re-check
> (don't know if something has been changed in this area since January). If
> you know something please let me know.

I mostly don't want to lose the comment if it is still useful.

> 
> [1]
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/mach-at91/pm.c#n290
> 
> > 
> >>
> >> 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?
> 
> By mistake. I'll switch to iomem reading wrapper.
> 
> Is it OK to send soon a new version with these adjustments or do you have
> other patches in this series to review?
> 

Feel free to resend.