Re: [PATCH 2/2] soc: imx: gpcv2: prepare bus clocks early

[Marek Vasut <marex@denx.de>]

On 6/2/23 20:54, Lucas Stach wrote:
> Prepare the bus clocks during PGC domain driver probe. This avoids a
> potential deadlock when there a clock providers inside the domain,
> as this might end up trying to take the CCF prepare_lock from two
> different contexts, when runtime PM is trying to resume the PGC domain
> for the clock provider. By keeping the bus clocks prepared as long as
> there is a PGC domain driver attached, we don't need to take the
> prepare_lock in the domain power up/down paths.
> 
> We don't want to do this for regular reset clocks, as this might lead
> to some PLLs being kept prepared that could otherwise be shut down.
> For the bus clocks this isn't a concern, as all the bus clocks are
> derived from always-on system PLLs.
> 
> Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> ---
>   drivers/soc/imx/gpcv2.c | 41 ++++++++++++++++++++++++++++++++++-------
>   1 file changed, 34 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/soc/imx/gpcv2.c b/drivers/soc/imx/gpcv2.c
> index 706f852e5d87..428e2fd82f26 100644
> --- a/drivers/soc/imx/gpcv2.c
> +++ b/drivers/soc/imx/gpcv2.c
> @@ -337,10 +337,14 @@ static int imx_pgc_power_up(struct generic_pm_domain *genpd)
>   
>   	reset_control_assert(domain->reset);
>   
> -	/* Enable reset clocks for all devices in the domain */
> -	ret = clk_bulk_prepare_enable(domain->num_clks, domain->clks);
> +	if (!domain->bus_clocks)
> +		/* Enable reset clocks for all devices in the domain */
> +		ret = clk_bulk_prepare_enable(domain->num_clks, domain->clks);
> +	else
> +		/* Enable bus clocks for this domain */
> +		ret = clk_bulk_enable(domain->num_clks, domain->clks);
>   	if (ret) {
> -		dev_err(domain->dev, "failed to enable reset clocks\n");
> +		dev_err(domain->dev, "failed to enable clocks\n");
>   		goto out_regulator_disable;
>   	}
>   
> @@ -402,7 +406,10 @@ static int imx_pgc_power_up(struct generic_pm_domain *genpd)
>   	return 0;
>   
>   out_clk_disable:
> -	clk_bulk_disable_unprepare(domain->num_clks, domain->clks);
> +	if (!domain->bus_clocks)
> +		clk_bulk_disable_unprepare(domain->num_clks, domain->clks);
> +	else
> +		clk_bulk_disable(domain->num_clks, domain->clks);
>   out_regulator_disable:
>   	if (!IS_ERR(domain->regulator))
>   		regulator_disable(domain->regulator);
> @@ -466,8 +473,11 @@ static int imx_pgc_power_down(struct generic_pm_domain *genpd)
>   		}
>   	}
>   
> -	/* Disable reset clocks for all devices in the domain */
> -	clk_bulk_disable_unprepare(domain->num_clks, domain->clks);
> +	/* Disable bus or reset clocks for all devices in the domain */
> +	if (!domain->bus_clocks)
> +		clk_bulk_disable_unprepare(domain->num_clks, domain->clks);
> +	else
> +		clk_bulk_disable(domain->num_clks, domain->clks);
>   
>   	if (!IS_ERR(domain->regulator)) {
>   		ret = regulator_disable(domain->regulator);
> @@ -486,6 +496,8 @@ static int imx_pgc_power_down(struct generic_pm_domain *genpd)
>   out_clk_disable:
>   	if (!domain->bus_clocks)
>   		clk_bulk_disable_unprepare(domain->num_clks, domain->clks);
> +	else
> +		clk_bulk_disable(domain->num_clks, domain->clks);
>   
>   	return ret;
>   }
> @@ -1343,10 +1355,19 @@ static int imx_pgc_domain_probe(struct platform_device *pdev)
>   		regmap_update_bits(domain->regmap, domain->regs->map,
>   				   domain->bits.map, domain->bits.map);
>   
> +	if (domain->bus_clocks) {
> +		ret = clk_bulk_prepare(domain->num_clks, domain->clks);
> +		if (ret) {
> +			dev_err(domain->dev,
> +				"Failed to prepare domain's clocks\n");
> +			goto out_domain_unmap;
> +		}
> +	}
> +
>   	ret = pm_genpd_init(&domain->genpd, NULL, true);
>   	if (ret) {
>   		dev_err(domain->dev, "Failed to init power domain\n");
> -		goto out_domain_unmap;
> +		goto out_disable_clocks;
>   	}
>   
>   	if (IS_ENABLED(CONFIG_LOCKDEP) &&
> @@ -1364,6 +1385,9 @@ static int imx_pgc_domain_probe(struct platform_device *pdev)
>   
>   out_genpd_remove:
>   	pm_genpd_remove(&domain->genpd);
> +out_disable_clocks:
> +	if (domain->bus_clocks)
> +		clk_bulk_unprepare(domain->num_clks, domain->clks);
>   out_domain_unmap:
>   	if (domain->bits.map)
>   		regmap_update_bits(domain->regmap, domain->regs->map,
> @@ -1380,6 +1404,9 @@ static int imx_pgc_domain_remove(struct platform_device *pdev)
>   	of_genpd_del_provider(domain->dev->of_node);
>   	pm_genpd_remove(&domain->genpd);
>   
> +	if (domain->bus_clocks)
> +		clk_bulk_unprepare(domain->num_clks, domain->clks);
> +
>   	if (domain->bits.map)
>   		regmap_update_bits(domain->regmap, domain->regs->map,
>   				   domain->bits.map, 0);

Isn't this similar approach to

[PATCH] [RFC] soc: imx: gpcv2: Split clock prepare from clock enable in 
the domain

where Laurent (now on CC) reported that this still causes issues ?

If not, then please ignore my comment here.

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