linux-kernel - Re: [PATCH 14/16] soc: imx: gpcv2: move reset assert after requesting domain power up

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Date:   Thu, 29 Apr 2021 16:28:43 +0200
From:   Lucas Stach <l.stach@...gutronix.de>
To:     "Peng Fan (OSS)" <peng.fan@....nxp.com>, robh+dt@...nel.org,
        shawnguo@...nel.org, s.hauer@...gutronix.de
Cc:     kernel@...gutronix.de, festevam@...il.com, linux-imx@....com,
        p.zabel@...gutronix.de, krzk@...nel.org, agx@...xcpu.org,
        marex@...x.de, andrew.smirnov@...il.com,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, ping.bai@....com,
        frieder.schrempf@...tron.de, aford173@...il.com, abel.vesa@....com,
        Peng Fan <peng.fan@....com>
Subject: Re: [PATCH 14/16] soc: imx: gpcv2: move reset assert after
 requesting domain power up

Am Donnerstag, dem 29.04.2021 um 15:30 +0800 schrieb Peng Fan (OSS):
> From: Peng Fan <peng.fan@....com>
> 
> The i.MX8MM VPU power up sequence is a bit special, it must follow:
> 1. request power up
> 2. reset assert
> 3. reset deassert
> 
> This change in this patch will not affect other domains, because
> the power domain default is in asserted state, unless bootloader
> deassert the reset.
> 
> [Note: We expect bootloader leave the domain in asserted state,
> but this may not always be true, so we might need another solution
> to address the VPU domain requirements]

This is only about the VPU and GPU domain, where we need to handle the
SRC reset from the GPC driver right? In that case I think it's a sane
assumption that the bootloader does not touch those resets.

> Signed-off-by: Peng Fan <peng.fan@....com>
> ---
>  drivers/soc/imx/gpcv2.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/soc/imx/gpcv2.c b/drivers/soc/imx/gpcv2.c
> index d2ce47a5ebad..072f519462a5 100644
> --- a/drivers/soc/imx/gpcv2.c
> +++ b/drivers/soc/imx/gpcv2.c
> @@ -217,8 +217,6 @@ static int imx_pgc_power_up(struct generic_pm_domain *genpd)
>  		goto out_regulator_disable;
>  	}
>  
> 
> 
> 
> 
> 
> 
> 
> -	reset_control_assert(domain->reset);
> -
>  	if (domain->bits.pxx) {
>  		/* request the domain to power up */
>  		regmap_update_bits(domain->regmap, GPC_PU_PGC_SW_PUP_REQ,
> @@ -241,6 +239,8 @@ static int imx_pgc_power_up(struct generic_pm_domain *genpd)
>  				   GPC_PGC_CTRL_PCR, 0);
>  	}
>  
> 
> 
> 
> 
> 
> 
> 
> +	reset_control_assert(domain->reset);
> +
>  	/* delay for reset to propagate */
>  	udelay(5);

As this is a pretty arbitrary delay added by me, can you please check
with the HW team or whoever knows, if this is sufficiently long for
both GPU and VPU domains?

Regards,
Lucas