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From: Lucas Stach <l.stach@pengutronix.de>
To: "Lothar Waßmann" <LW@KARO-electronics.de>
Cc: "A.S. Dong" <aisheng.dong@nxp.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"patchwork-lst@pengutronix.de" <patchwork-lst@pengutronix.de>,
	"kernel@pengutronix.de" <kernel@pengutronix.de>,
	Fabio Estevam <fabio.estevam@nxp.com>,
	Shawn Guo <shawnguo@kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 2/2] soc/imx: add workaround for i.MX6QP to the GPC PD driver
Date: Thu, 30 Mar 2017 10:22:17 +0200	[thread overview]
Message-ID: <1490862137.29083.30.camel@pengutronix.de> (raw)
In-Reply-To: <20170330090833.09ac3c33@ipc1.ka-ro>

Am Donnerstag, den 30.03.2017, 09:08 +0200 schrieb Lothar Waßmann:
> Hi,
> 
> On Wed, 29 Mar 2017 18:13:46 +0200 Lucas Stach wrote:
> > Am Mittwoch, den 29.03.2017, 16:08 +0000 schrieb A.S. Dong:
> > > Hi Lucas,
> > > 
> > > > -----Original Message-----
> > > > From: Lucas Stach [mailto:l.stach@pengutronix.de]
> > > > Sent: Thursday, March 23, 2017 10:44 PM
> > > > To: Shawn Guo
> > > > Cc: Fabio Estevam; A.S. Dong; devicetree@vger.kernel.org; linux-arm-
> > > > kernel@lists.infradead.org; kernel@pengutronix.de; patchwork-
> > > > lst@pengutronix.de
> > > > Subject: [PATCH 2/2] soc/imx: add workaround for i.MX6QP to the GPC PD
> > > > driver
> > > > 
> > > > On i.MX6QP, due to hardware erratum ERR009619, the PRE clocks may be
> > > > stalled during the power up sequencing of the PU power domain. As this may
> > > > lead to a complete loss of display output, the recommended workaround is
> > > > to keep the PU domain enabled during normal system operation.
> > > > 
> > > > Implement this by rejecting the domain power down request on the affected
> > > > SoC.
> > > > 
> > > > Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> > > > ---
> > > >  drivers/soc/imx/gpc.c | 19 +++++++++++++++++++
> > > >  1 file changed, 19 insertions(+)
> > > > 
> > > > diff --git a/drivers/soc/imx/gpc.c b/drivers/soc/imx/gpc.c index
> > > > 4294287e5f6c..599e1e46f694 100644
> > > > --- a/drivers/soc/imx/gpc.c
> > > > +++ b/drivers/soc/imx/gpc.c
> > > > @@ -45,6 +45,7 @@ struct imx_pm_domain {
> > > >  	unsigned int reg_offs;
> > > >  	signed char cntr_pdn_bit;
> > > >  	unsigned int ipg_rate_mhz;
> > > > +	bool allow_dynamic_pd;
> > > >  };
> > > > 
> > > >  static inline struct imx_pm_domain *
> > > > @@ -59,6 +60,9 @@ static int imx6_pm_domain_power_off(struct
> > > > generic_pm_domain *genpd)
> > > >  	int iso, iso2sw;
> > > >  	u32 val;
> > > > 
> > > > +	if (!pd->allow_dynamic_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;
> > > > @@ -255,6 +259,7 @@ static struct imx_pm_domain imx_gpc_domains[] = {
> > > >  		},
> > > >  		.reg_offs = 0x260,
> > > >  		.cntr_pdn_bit = 0,
> > > > +		.allow_dynamic_pd = true,
> > > >  	}, {
> > > >  		.base = {
> > > >  			.name = "DISPLAY",
> > > > @@ -263,23 +268,33 @@ static struct imx_pm_domain imx_gpc_domains[] = {
> > > >  		},
> > > >  		.reg_offs = 0x240,
> > > >  		.cntr_pdn_bit = 4,
> > > > +		.allow_dynamic_pd = true,
> > > 
> > > Just a Nitpick, besides shawn's comment in another mail,
> > > if we use a domain flag like IMX_PD_ALWAYS_ON set by SoC errata flag,
> > > then probably we can save all the default allow_dynamic_pd lines.
> > > This also release the life when adding new domains.
> > 
> > If other things like that show up we can certainly switch to a flags
> > field. In the meantime I like that the current style is more explicit
> > about it.
> > 
> Since the purpose of the driver is all about dynamic power management,
> I would rather add a 'disable_dynamic_pd' for the case(s) where it's
> not allowed, rather than having to state the obvious over and over
> again.

Convincing argument. I'll change that in v2.

Regards,
Lucas



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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

      reply	other threads:[~2017-03-30  8:22 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-23 14:44 [PATCH 0/2] i.MX6QP GPC fixes Lucas Stach
     [not found] ` <20170323144418.30977-1-l.stach-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2017-03-23 14:44   ` [PATCH 1/2] dt-bindings: imx-gpc: add i.MX6 QuadPlus compatible Lucas Stach
     [not found]     ` <20170323144418.30977-2-l.stach-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2017-03-29 15:59       ` Rob Herring
2017-03-23 14:44   ` [PATCH 2/2] soc/imx: add workaround for i.MX6QP to the GPC PD driver Lucas Stach
     [not found]     ` <20170323144418.30977-3-l.stach-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2017-03-24  6:28       ` Shawn Guo
2017-03-29 16:08       ` A.S. Dong
     [not found]         ` <DB5PR04MB1431A7CC91F55ECFE5BE31FB80350-rqLcZCCNzVwrYIBjo4yUUM9NdZoXdze2vxpqHgZTriW3zl9H0oFU5g@public.gmane.org>
2017-03-29 16:13           ` Lucas Stach
2017-03-30  7:08             ` Lothar Waßmann
2017-03-30  8:22               ` Lucas Stach [this message]

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