linux-kernel - Re: [PATCH/RFC] clk: qcom: rpmh: Block system suspend if XO is enabled

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Date:   Thu, 30 Jun 2022 23:00:11 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, patches@...ts.linux.dev,
        linux-arm-msm@...r.kernel.org, Taniya Das <quic_tdas@...cinc.com>,
        Mike Tipton <quic_mdtipton@...cinc.com>
Subject: Re: [PATCH/RFC] clk: qcom: rpmh: Block system suspend if XO is
 enabled

On Tue 28 Jun 15:13 CDT 2022, Stephen Boyd wrote:

> Tracking down what RPMh resource is blocking XO shutdown in suspend is
> hard. Largely because we need external debug tools to dump the RPMh
> internal state to figure out what resource is enabled. Instead of doing
> that, let's just block system wide suspend in the kernel if the RPMh XO
> resource is enabled by something in the kernel. This will help us narrow
> down XO shutdown failures to the XO clk, and not something else like an
> interconnect or regulator RPMh resource.
> 
> I'm sending this as an RFC because it breaks suspend for me on Trogdor
> boards. I found out that the XO resource is always enabled on these
> devices because the audio driver leaves an audio clk always on. This
> means that the XO resource must not be used to determine if XO shutdown
> is achievable, or we're leaving power savings on the table.
> 
> Cc: Taniya Das <quic_tdas@...cinc.com>
> Cc: Mike Tipton <quic_mdtipton@...cinc.com>
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>

Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>

> ---
> 
> Please don't apply. It will break suspend on Trogdor boards.
> 

This seems like a useful debug feature for people outside of Qualcomm,
so I assume you're saying that we shouldn't merge it until someone has
fixed the audio driver? Or did you post it just as a debug tool?

Regards,
Bjorn

>  drivers/clk/qcom/clk-rpmh.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/clk/qcom/clk-rpmh.c b/drivers/clk/qcom/clk-rpmh.c
> index aed907982344..ba0e0e4b9cf2 100644
> --- a/drivers/clk/qcom/clk-rpmh.c
> +++ b/drivers/clk/qcom/clk-rpmh.c
> @@ -70,6 +70,14 @@ struct clk_rpmh_desc {
>  
>  static DEFINE_MUTEX(rpmh_clk_lock);
>  
> +/* XO shutdown will fail if XO is enabled across suspend */
> +static int clk_rpmh_suspend(struct device *dev)
> +{
> +	struct clk_rpmh *xo = dev_get_drvdata(dev);
> +
> +	return xo && xo->state ? -EBUSY : 0;
> +}
> +
>  #define __DEFINE_CLK_RPMH(_platform, _name, _name_active, _res_name,	\
>  			  _res_en_offset, _res_on, _div)		\
>  	static struct clk_rpmh _platform##_##_name_active;		\
> @@ -690,6 +698,10 @@ static int clk_rpmh_probe(struct platform_device *pdev)
>  			dev_err(&pdev->dev, "failed to register %s\n", name);
>  			return ret;
>  		}
> +
> +		/* Stash CXO clk for XO shutdown tracking */
> +		if (i == RPMH_CXO_CLK)
> +			platform_set_drvdata(pdev, rpmh_clk);
>  	}
>  
>  	/* typecast to silence compiler warning */
> @@ -722,9 +734,12 @@ static const struct of_device_id clk_rpmh_match_table[] = {
>  };
>  MODULE_DEVICE_TABLE(of, clk_rpmh_match_table);
>  
> +static SIMPLE_DEV_PM_OPS(clk_rpmh_pm_ops, clk_rpmh_suspend, NULL);
> +
>  static struct platform_driver clk_rpmh_driver = {
>  	.probe		= clk_rpmh_probe,
>  	.driver		= {
> +		.pm	= pm_ptr(&clk_rpmh_pm_ops),
>  		.name	= "clk-rpmh",
>  		.of_match_table = clk_rpmh_match_table,
>  	},
> 
> base-commit: f2906aa863381afb0015a9eb7fefad885d4e5a56
> -- 
> https://chromeos.dev
>