linux-kernel - Re: [PATCH V2 13/13] soc: imx: gpcv2: move reset assert after requesting domain power up

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Date:   Thu, 6 May 2021 08:56:35 +0200
From:   Frieder Schrempf <frieder.schrempf@...tron.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, l.stach@...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, aford173@...il.com,
        abel.vesa@....com, Peng Fan <peng.fan@....com>
Subject: Re: [PATCH V2 13/13] soc: imx: gpcv2: move reset assert after
 requesting domain power up

On 06.05.21 03:04, Peng Fan (OSS) wrote:
> 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. It also applies to GPU power domain.
> 
> Signed-off-by: Peng Fan <peng.fan@....com>

I don't really like that there is a dependency on TF-A/bootloader as we never really know what they will do, but from my point of view the approach is ok and it seems to work properly as far as I have tested it (only with GPU).

Reviewed-by: Frieder Schrempf <frieder.schrempf@...tron.de>
Tested-by: Frieder Schrempf <frieder.schrempf@...tron.de>

> ---
>  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 65b562cbcc6d..325a34833ffa 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);
>  	}
>  
> +	reset_control_assert(domain->reset);
> +
>  	/* delay for reset to propagate */
>  	udelay(5);
>  
>