linux-kernel - Re: [PATCH v3 1/2] soc: imx: gpc: Disable 6sl display power gating for ERR006287

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Date:   Wed, 11 Jul 2018 14:16:32 +0200
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Leonard Crestez <leonard.crestez@....com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Shawn Guo <shawnguo@...nel.org>
Cc:     Fabio Estevam <fabio.estevam@....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 v3 1/2] soc: imx: gpc: Disable 6sl display power gating
 for ERR006287

Am Mittwoch, den 11.07.2018, 15:11 +0300 schrieb Leonard Crestez:
> The imx6sl chip errata document describes ERR006287 like this:
> 
> > Upon resuming from power gating, the modules in the display power domain
> 
> (eLCDIF, EPDC, PXP and SPDC) might fail to perform register reads
> correctly.
> 
> > When the modules listed above are used, do not use power gating on the
> 
> display power domain.
> 
> Link: https://www.nxp.com/docs/en/errata/IMX6SLCE.pdf#page=62
> 
> Handle this in the safest possible way by keeping the DISP domain
> always-on.
> 
> Signed-off-by: Leonard Crestez <leonard.crestez@....com>

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

Can you send a follow on patch to switch the i.MX6QP errata workaround
to use GENPD_FLAG_ALWAYS_ON and remove the -EBUSY stuff in the power
down path?

Regards,
Lucas

> ---
>  drivers/soc/imx/gpc.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/soc/imx/gpc.c b/drivers/soc/imx/gpc.c
> index 526f2d02dc78..f7960f773019 100644
> --- a/drivers/soc/imx/gpc.c
> +++ b/drivers/soc/imx/gpc.c
> @@ -339,30 +339,35 @@ static struct imx_pm_domain imx_gpc_domains[] = {
>  };
>  
>  struct imx_gpc_dt_data {
> >  	int num_domains;
> >  	bool err009619_present;
> > +	bool err006287_present;
>  };
>  
>  static const struct imx_gpc_dt_data imx6q_dt_data = {
> >  	.num_domains = 2,
> >  	.err009619_present = false,
> > +	.err006287_present = false,
>  };
>  
>  static const struct imx_gpc_dt_data imx6qp_dt_data = {
> >  	.num_domains = 2,
> >  	.err009619_present = true,
> > +	.err006287_present = false,
>  };
>  
>  static const struct imx_gpc_dt_data imx6sl_dt_data = {
> >  	.num_domains = 3,
> >  	.err009619_present = false,
> > +	.err006287_present = true,
>  };
>  
>  static const struct imx_gpc_dt_data imx6sx_dt_data = {
> >  	.num_domains = 4,
> >  	.err009619_present = false,
> > +	.err006287_present = false,
>  };
>  
>  static const struct of_device_id imx_gpc_dt_ids[] = {
> >  	{ .compatible = "fsl,imx6q-gpc", .data = &imx6q_dt_data },
> >  	{ .compatible = "fsl,imx6qp-gpc", .data = &imx6qp_dt_data },
> @@ -467,10 +472,15 @@ static int imx_gpc_probe(struct platform_device *pdev)
> >  	/* 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;
>  
> > +	/* 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;
> +
> >  	if (!pgc_node) {
> >  		ret = imx_gpc_old_dt_init(&pdev->dev, regmap,
> >  					  of_id_data->num_domains);
> >  		if (ret)
> >  			return ret;