linux-kernel - Re: [PATCH v6 1/3] clk: at91: pmc: Wait for clocks when resuming

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Date:   Tue, 19 Dec 2017 23:25:15 +0100
From:   Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:     Romain Izard <romain.izard.pro@...il.com>
Cc:     Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v6 1/3] clk: at91: pmc: Wait for clocks when resuming

On 11/12/2017 at 17:55:33 +0100, Romain Izard wrote:
> Wait for the syncronization of all clocks when resuming, not only the
> UPLL clock. Do not use regmap_read_poll_timeout, as it will call BUG()
> when interrupts are masked, which is the case in here.
> 
> Signed-off-by: Romain Izard <romain.izard.pro@...il.com>
> Acked-by: Ludovic Desroches <ludovic.desroches@...rochip.com>
> Acked-by: Nicolas Ferre <nicolas.ferre@...rochip.com>
Acked-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>

> ---
>  drivers/clk/at91/pmc.c | 24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/clk/at91/pmc.c b/drivers/clk/at91/pmc.c
> index 775af473fe11..5c2b26de303e 100644
> --- a/drivers/clk/at91/pmc.c
> +++ b/drivers/clk/at91/pmc.c
> @@ -107,10 +107,20 @@ static int pmc_suspend(void)
>  	return 0;
>  }
>  
> +static bool pmc_ready(unsigned int mask)
> +{
> +	unsigned int status;
> +
> +	regmap_read(pmcreg, AT91_PMC_SR, &status);
> +
> +	return ((status & mask) == mask) ? 1 : 0;
> +}
> +
>  static void pmc_resume(void)
>  {
> -	int i, ret = 0;
> +	int i;
>  	u32 tmp;
> +	u32 mask = AT91_PMC_MCKRDY | AT91_PMC_LOCKA;
>  
>  	regmap_read(pmcreg, AT91_PMC_MCKR, &tmp);
>  	if (pmc_cache.mckr != tmp)
> @@ -134,13 +144,11 @@ static void pmc_resume(void)
>  			     AT91_PMC_PCR_CMD);
>  	}
>  
> -	if (pmc_cache.uckr & AT91_PMC_UPLLEN) {
> -		ret = regmap_read_poll_timeout(pmcreg, AT91_PMC_SR, tmp,
> -					       !(tmp & AT91_PMC_LOCKU),
> -					       10, 5000);
> -		if (ret)
> -			pr_crit("USB PLL didn't lock when resuming\n");
> -	}
> +	if (pmc_cache.uckr & AT91_PMC_UPLLEN)
> +		mask |= AT91_PMC_LOCKU;
> +
> +	while (!pmc_ready(mask))
> +		cpu_relax();
>  }
>  
>  static struct syscore_ops pmc_syscore_ops = {
> -- 
> 2.14.1
> 

-- 
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com