linux-kernel - Re: [PATCH] soc: imx6qp: Use GENPD_FLAG_ALWAYS

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Date:   Fri, 13 Jul 2018 12:29:26 +0200
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Leonard Crestez <leonard.crestez@....com>,
        Shawn Guo <shawnguo@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Fabio Estevam <fabio.estevam@....com>,
        Robin Gong <yibin.gong@....com>,
        Anson Huang <Anson.Huang@....com>,
        Dong Aisheng <aisheng.dong@....com>, linux-pm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-imx@....com, kernel@...gutronix.de
Subject: Re: [PATCH] soc: imx6qp: Use GENPD_FLAG_ALWAYS_ON for PU errata

Am Freitag, den 13.07.2018, 13:01 +0300 schrieb Leonard Crestez:
> This is functionally identical but simpler and slightly faster.
> 
> The PU domain is turned on at boot time and never turned off. In the
> current implementation the pm core will repeatedly call power_off when
> the domain is unused and get -EBUSY back. If the domain is marked as
> "always on" instead the pm core won't even attempt to turn it off.
> 
> In theory on 6qp it is safe to turn PU off in suspend, however that is
> best accomplished with a new core flag.
> 
> Signed-off-by: Leonard Crestez <leonard.crestez@....com>

Reviewed-by: Lucas Stach <l.stach@...gutronix.de>

> ---
>  drivers/soc/imx/gpc.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> Previous discussion:
> * https://lkml.org/lkml/2018/7/11/431
> * https://lkml.org/lkml/2018/7/10/103
> 
> Attempt at turning PU off in suspend:
> * https://lkml.org/lkml/2018/7/6/698
> 
> diff --git a/drivers/soc/imx/gpc.c b/drivers/soc/imx/gpc.c
> index faf13a0b85d6..f31978e5af20 100644
> --- a/drivers/soc/imx/gpc.c
> +++ b/drivers/soc/imx/gpc.c
> @@ -45,11 +45,10 @@ struct imx_pm_domain {
> >  	struct clk *clk[GPC_CLK_MAX];
> >  	int num_clks;
> >  	unsigned int reg_offs;
> >  	signed char cntr_pdn_bit;
> >  	unsigned int ipg_rate_mhz;
> > -	unsigned int flags;
>  };
>  
>  static inline struct imx_pm_domain *
>  to_imx_pm_domain(struct generic_pm_domain *genpd)
>  {
> @@ -60,13 +59,10 @@ static int imx6_pm_domain_power_off(struct generic_pm_domain *genpd)
>  {
> >  	struct imx_pm_domain *pd = to_imx_pm_domain(genpd);
> >  	int iso, iso2sw;
> >  	u32 val;
>  
> > -	if (pd->flags & PGC_DOMAIN_FLAG_NO_PD)
> > -		return -EBUSY;
> -
> >  	/* Read ISO and ISO2SW power down delays */
> >  	regmap_read(pd->regmap, pd->reg_offs + GPC_PGC_PUPSCR_OFFS, &val);
> >  	iso = val & 0x3f;
> >  	iso2sw = (val >> 8) & 0x3f;
>  
> @@ -419,12 +415,12 @@ static int imx_gpc_probe(struct platform_device *pdev)
> >  		return ret;
> >  	}
>  
> >  	/* Disable PU power down in normal operation if ERR009619 is present */
> >  	if (of_id_data->err009619_present)
> > -		imx_gpc_domains[GPC_PGC_DOMAIN_PU].flags |=
> > -				PGC_DOMAIN_FLAG_NO_PD;
> > +		imx_gpc_domains[GPC_PGC_DOMAIN_PU].base.flags |=
> > +				GENPD_FLAG_ALWAYS_ON;
>  
> >  	/* Keep DISP always on if ERR006287 is present */
> >  	if (of_id_data->err006287_present)
> >  		imx_gpc_domains[GPC_PGC_DOMAIN_DISPLAY].base.flags |=
> >  				GENPD_FLAG_ALWAYS_ON;