linux-kernel - Re: [PATCH v1 5/7] soc: mediatek: add a fixed wait for SRAM stable

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Date:   Fri, 20 Apr 2018 11:49:50 +0800
From:   Sean Wang <sean.wang@...iatek.com>
To:     Matthias Brugger <matthias.bgg@...il.com>
CC:     <robh+dt@...nel.org>, <mark.rutland@....com>,
        <marcel@...tmann.org>, <johan.hedberg@...il.com>,
        <devicetree@...r.kernel.org>, <linux-bluetooth@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        "Ulf Hansson" <ulf.hansson@...aro.org>,
        Weiyi Lu <weiyi.lu@...iatek.com>
Subject: Re: [PATCH v1 5/7] soc: mediatek: add a fixed wait for SRAM stable

On Thu, 2018-04-19 at 12:33 +0200, Matthias Brugger wrote:
> 
> On 04/03/2018 09:15 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.
> > 
> > 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 | 17 ++++++++++++-----
> >  1 file changed, 12 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/soc/mediatek/mtk-scpsys.c b/drivers/soc/mediatek/mtk-scpsys.c
> > index f9b7248..19aceb8 100644
> > --- a/drivers/soc/mediatek/mtk-scpsys.c
> > +++ b/drivers/soc/mediatek/mtk-scpsys.c
> > @@ -121,6 +121,7 @@ struct scp_domain_data {
> >  	u32 bus_prot_mask;
> >  	enum clk_id clk_id[MAX_CLKS];
> >  	bool active_wakeup;
> > +	u32 us_sram_fwait;
> 
> Before adding more and more fields to scp_domain_data which get checked in if's,
> I'd prefer to add a caps field used for bus_prot_mask, active_wakeup in a first
> patch and add the cap FORCE_WAIT in a second patch.
> 
> Can you help to implement this Sean, or shall I give it a try?
> 

Sure, I have a willing to do and then see if you're also fond of it.

thanks!

> Regards,
> Matthias
> 
> >  };
> >  
> >  struct scp;
> > @@ -234,11 +235,16 @@ 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 (!scpd->data->us_sram_fwait) {
> > +		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 {
> > +		usleep_range(scpd->data->us_sram_fwait,
> > +			     scpd->data->us_sram_fwait + 100);
> > +	};
> >  
> >  	if (scpd->data->bus_prot_mask) {
> >  		ret = mtk_infracfg_clear_bus_protection(scp->infracfg,
> > @@ -783,6 +789,7 @@ static const struct scp_domain_data scp_domain_data_mt7622[] = {
> >  		.clk_id = {CLK_NONE},
> >  		.bus_prot_mask = MT7622_TOP_AXI_PROT_EN_WB,
> >  		.active_wakeup = true,
> > +		.us_sram_fwait = 12000,
> >  	},
> >  };
> >  
> >