linux-kernel - Re: [PATCH v2 2/2] soc: mediatek: add a fixed wait for SRAM stable

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Date:   Mon, 23 Apr 2018 17:39:00 +0800
From:   Sean Wang <sean.wang@...iatek.com>
To:     Matthias Brugger <matthias.bgg@...il.com>
CC:     <rjw@...ysocki.net>, <khilman@...libre.com>,
        <ulf.hansson@...aro.org>, <linux-mediatek@...ts.infradead.org>,
        <linux-pm@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, "Weiyi Lu" <weiyi.lu@...iatek.com>
Subject: Re: [PATCH v2 2/2] soc: mediatek: add a fixed wait for SRAM stable

On Mon, 2018-04-23 at 11:31 +0200, Matthias Brugger wrote:
> 
> On 04/23/2018 10:36 AM, sean.wang@...iatek.com wrote:
> > From: Sean Wang <sean.wang@...iatek.com>
> > 
> > MT7622_POWER_DOMAIN_WB doesn't send an ACK when its managed SRAM becomes
> > stable, which is not like the behavior the other power domains should
> > have. Therefore, it's necessary for such a power domain to have a fixed
> > and well-predefined duration to wait until its managed SRAM can be allowed
> > to access by all functions running on the top.
> > 
> > v1 -> v2:
> >  - use MTK_SCPD_FWAIT_SRAM flag as an indication requiring force waiting.
> > 
> > Signed-off-by: Sean Wang <sean.wang@...iatek.com>
> > Cc: Matthias Brugger <matthias.bgg@...il.com>
> > Cc: Ulf Hansson <ulf.hansson@...aro.org>
> > Cc: Weiyi Lu <weiyi.lu@...iatek.com>
> > ---
> >  drivers/soc/mediatek/mtk-scpsys.c | 24 ++++++++++++++++++------
> >  1 file changed, 18 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/soc/mediatek/mtk-scpsys.c b/drivers/soc/mediatek/mtk-scpsys.c
> > index b1b45e4..d4f1a63 100644
> > --- a/drivers/soc/mediatek/mtk-scpsys.c
> > +++ b/drivers/soc/mediatek/mtk-scpsys.c
> > @@ -32,6 +32,7 @@
> >  #define MTK_POLL_TIMEOUT    (jiffies_to_usecs(HZ))
> >  
> >  #define MTK_SCPD_ACTIVE_WAKEUP		BIT(0)
> > +#define MTK_SCPD_FWAIT_SRAM		BIT(1)
> >  #define MTK_SCPD_CAPS(_scpd, _x)	((_scpd)->data->caps & (_x))
> >  
> >  #define SPM_VDE_PWR_CON			0x0210
> > @@ -237,11 +238,22 @@ static int scpsys_power_on(struct generic_pm_domain *genpd)
> >  	val &= ~scpd->data->sram_pdn_bits;
> >  	writel(val, ctl_addr);
> >  
> > -	/* wait until SRAM_PDN_ACK all 0 */
> > -	ret = readl_poll_timeout(ctl_addr, tmp, (tmp & pdn_ack) == 0,
> > -				 MTK_POLL_DELAY_US, MTK_POLL_TIMEOUT);
> > -	if (ret < 0)
> > -		goto err_pwr_ack;
> > +	/* Either wait until SRAM_PDN_ACK all 0 or have a force wait */
> > +	if (!MTK_SCPD_CAPS(scpd, MTK_SCPD_FWAIT_SRAM)) {
> > +		ret = readl_poll_timeout(ctl_addr, tmp, (tmp & pdn_ack) == 0,
> > +					 MTK_POLL_DELAY_US, MTK_POLL_TIMEOUT);
> > +		if (ret < 0)
> > +			goto err_pwr_ack;
> > +	} else {
> > +		/*
> > +		 * Currently, MTK_SCPD_FWAIT_SRAM is necessary only for
> > +		 * MT7622_POWER_DOMAIN_WB and thus just a trivial setup is
> > +		 * applied here. If there're more domains which need to force
> > +		 * waiting for its own pre-defined value, the duration should
> > +		 * be coded in the caps field.
> > +		 */
> 
> I would say, if necessary in the future we can add a switch statement here.
> Other then that the patches look good. If you are OK, I'll just delete the last
> sentence when applying the patch.
> 

yes, it's okay for me. 

> Regards,
> Matthias
> 
> > +		usleep_range(12000, 12100);
> > +	};
> >  
> >  	if (scpd->data->bus_prot_mask) {
> >  		ret = mtk_infracfg_clear_bus_protection(scp->infracfg,
> > @@ -785,7 +797,7 @@ static const struct scp_domain_data scp_domain_data_mt7622[] = {
> >  		.sram_pdn_ack_bits = 0,
> >  		.clk_id = {CLK_NONE},
> >  		.bus_prot_mask = MT7622_TOP_AXI_PROT_EN_WB,
> > -		.caps = MTK_SCPD_ACTIVE_WAKEUP,
> > +		.caps = MTK_SCPD_ACTIVE_WAKEUP | MTK_SCPD_FWAIT_SRAM,
> >  	},
> >  };
> >  
> >