linux-kernel - Re: [PATCH 3/4] soc: mediatek: add support of MTK_SCPD_STRICT

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Message-ID: <20220721085547.unr5cu4kywpugxmx@blmsp>
Date:   Thu, 21 Jul 2022 10:55:47 +0200
From:   Markus Schneider-Pargmann <msp@...libre.com>
To:     Matthias Brugger <matthias.bgg@...il.com>
Cc:     Fabien Parent <fparent@...libre.com>,
        Alexandre Bailon <abailon@...libre.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] soc: mediatek: add support of MTK_SCPD_STRICT_BUSP
 cap

Hi Matthias,

sorry, took a long time to respond.

On Fri, Jun 17, 2022 at 04:20:10PM +0200, Matthias Brugger wrote:
> 
> 
> On 30/05/2022 22:42, Fabien Parent wrote:
> > From: Alexandre Bailon <abailon@...libre.com>
> > 
> > This adds support of MTK_SCPD_STRICT_BUSP cap.
> > This is required by the mt8365, for the MM power domain.
> > 
> 
> Please explain better waht this flag is doing.

I will update the commit message as well.

The flag basically tells the code that there is a strict bus protection
policy in place which means that bus protect release must be before bus
access. This is not on all platforms the case.

> 
> > Signed-off-by: Alexandre Bailon <abailon@...libre.com>
> > Signed-off-by: Fabien Parent <fparent@...libre.com>
> > ---
> >   drivers/soc/mediatek/mtk-pm-domains.c | 37 ++++++++++++++++++++-------
> >   drivers/soc/mediatek/mtk-pm-domains.h |  1 +
> >   2 files changed, 29 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/soc/mediatek/mtk-pm-domains.c b/drivers/soc/mediatek/mtk-pm-domains.c
> > index 90b91b3b19a8..beaa5785fda2 100644
> > --- a/drivers/soc/mediatek/mtk-pm-domains.c
> > +++ b/drivers/soc/mediatek/mtk-pm-domains.c
> > @@ -263,17 +263,36 @@ static int scpsys_power_on(struct generic_pm_domain *genpd)
> >   	regmap_clear_bits(scpsys->base, pd->data->ctl_offs, PWR_ISO_BIT);
> >   	regmap_set_bits(scpsys->base, pd->data->ctl_offs, PWR_RST_B_BIT);
> > -	ret = clk_bulk_prepare_enable(pd->num_subsys_clks, pd->subsys_clks);
> > -	if (ret)
> > -		goto err_pwr_ack;
> 
> I think it would help readability if we would enable the clocks only in the
> case that MTK_SCPD_CAPS(pd, MTK_SCPD_STRICT_BUSP) is false. Then we would
> only need to add the same if to the error path of err_disable_subsys_clks,
> correct?

I already rearranged the code to have a cleaner flow for v2.

Thanks,
Markus

> 
> Regards,
> Matthias
> 
> > +	if (MTK_SCPD_CAPS(pd, MTK_SCPD_STRICT_BUSP)) {
> > +		/*
> > +		 * In few Mediatek platforms(e.g. MT6779), the bus protect
> > +		 * policy is stricter, which leads to bus protect release must
> > +		 * be prior to bus access.
> > +		 */
> > +		ret = scpsys_sram_enable(pd);
> > +		if (ret < 0)
> > +			goto err_pwr_ack;
> > -	ret = scpsys_sram_enable(pd);
> > -	if (ret < 0)
> > -		goto err_disable_subsys_clks;
> > +		ret = scpsys_bus_protect_disable(pd);
> > +		if (ret < 0)
> > +			goto err_pwr_ack;
> > -	ret = scpsys_bus_protect_disable(pd);
> > -	if (ret < 0)
> > -		goto err_disable_sram;
> > +		ret = clk_bulk_prepare_enable(pd->num_subsys_clks, pd->subsys_clks);
> > +		if (ret < 0)
> > +			goto err_pwr_ack;
> > +	} else {
> > +		ret = clk_bulk_prepare_enable(pd->num_subsys_clks, pd->subsys_clks);
> > +		if (ret)
> > +			goto err_pwr_ack;
> > +
> > +		ret = scpsys_sram_enable(pd);
> > +		if (ret < 0)
> > +			goto err_disable_subsys_clks;
> > +
> > +		ret = scpsys_bus_protect_disable(pd);
> > +		if (ret < 0)
> > +			goto err_disable_sram;
> > +	}
> >   	return 0;
> > diff --git a/drivers/soc/mediatek/mtk-pm-domains.h b/drivers/soc/mediatek/mtk-pm-domains.h
> > index a3955d960233..5347471bc3c4 100644
> > --- a/drivers/soc/mediatek/mtk-pm-domains.h
> > +++ b/drivers/soc/mediatek/mtk-pm-domains.h
> > @@ -8,6 +8,7 @@
> >   #define MTK_SCPD_SRAM_ISO		BIT(2)
> >   #define MTK_SCPD_KEEP_DEFAULT_OFF	BIT(3)
> >   #define MTK_SCPD_DOMAIN_SUPPLY		BIT(4)
> > +#define MTK_SCPD_STRICT_BUSP		BIT(5)
> >   #define MTK_SCPD_CAPS(_scpd, _x)	((_scpd)->data->caps & (_x))
> >   #define SPM_VDE_PWR_CON			0x0210
>