Re: [PATCH v4 05/14] soc: mediatek: mtk-svs: use svs clk control APIs

[Matthias Brugger <matthias.bgg@gmail.com>]

On 11/01/2023 08:45, Roger Lu wrote:
> In MediaTek HW design, svs and thermal both use the same clk source.
> It means that svs clk reference count from CCF includes thermal control
> counts. That makes svs driver confuse whether it disabled svs's main clk
> or not from CCF's perspective and lead to turn off their shared clk
> unexpectedly. Therefore, we add svs clk control APIs to make sure svs's
> main clk is controlled well by svs driver itself.
> 
> Here is a NG example. Rely on CCF's reference count and cause problem.
> 
> thermal probe (clk ref = 1)
> -> svs probe (clk ref = 2)
>     -> svs suspend (clk ref = 1)
>        -> thermal suspend (clk ref = 0)
>        -> thermal resume (clk ref = 1)
>     -> svs resume (encounter error, clk ref = 1)
>     -> svs suspend (clk ref = 0)
>        -> thermal suspend (Fail here, thermal HW control w/o clk)
> 
> Fixes: a825d72f74a3 ("soc: mediatek: fix missing clk_disable_unprepare() on err in svs_resume()")
> Signed-off-by: Roger Lu <roger.lu@mediatek.com>

That looks wrong. Although I don't out of my mind, there should be a way to tell 
the clock framework that this clock is shared between several devices.

I wonder if using clk_enable and clk_disable in svs_resume/suspend wouldn't be 
enough.

Regards,
Matthias

> ---
>   drivers/soc/mediatek/mtk-svs.c | 57 ++++++++++++++++++++++++++--------
>   1 file changed, 44 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/soc/mediatek/mtk-svs.c b/drivers/soc/mediatek/mtk-svs.c
> index 9575aa645643..830263bad81e 100644
> --- a/drivers/soc/mediatek/mtk-svs.c
> +++ b/drivers/soc/mediatek/mtk-svs.c
> @@ -326,6 +326,7 @@ static const u32 svs_regs_v2[] = {
>    * @bank_max: total number of svs banks
>    * @efuse: svs efuse data received from NVMEM framework
>    * @tefuse: thermal efuse data received from NVMEM framework
> + * @clk_cnt: clock count shows the clk enable/disable times by svs driver
>    */
>   struct svs_platform {
>   	char *name;
> @@ -343,6 +344,7 @@ struct svs_platform {
>   	u32 bank_max;
>   	u32 *efuse;
>   	u32 *tefuse;
> +	s32 clk_cnt;
>   };
>   
>   struct svs_platform_data {
> @@ -502,6 +504,32 @@ static void svs_switch_bank(struct svs_platform *svsp)
>   	svs_writel_relaxed(svsp, svsb->core_sel, CORESEL);
>   }
>   
> +static bool svs_is_clk_enabled(struct svs_platform *svsp)
> +{
> +	return svsp->clk_cnt > 0 ? true : false;
> +}
> +
> +static int svs_clk_enable(struct svs_platform *svsp)
> +{
> +	int ret;
> +
> +	ret = clk_prepare_enable(svsp->main_clk);
> +	if (ret) {
> +		dev_err(svsp->dev, "cannot enable main_clk: %d\n", ret);
> +		return ret;
> +	}
> +
> +	svsp->clk_cnt++;
> +
> +	return 0;
> +}
> +
> +static void svs_clk_disable(struct svs_platform *svsp)
> +{
> +	clk_disable_unprepare(svsp->main_clk);
> +	svsp->clk_cnt--;
> +}
> +
>   static u32 svs_bank_volt_to_opp_volt(u32 svsb_volt, u32 svsb_volt_step,
>   				     u32 svsb_volt_base)
>   {
> @@ -1569,6 +1597,12 @@ static int svs_suspend(struct device *dev)
>   	int ret;
>   	u32 idx;
>   
> +	if (!svs_is_clk_enabled(svsp)) {
> +		dev_err(svsp->dev, "svs clk is disabled already (%d)\n",
> +			svsp->clk_cnt);
> +		return 0;
> +	}
> +
>   	for (idx = 0; idx < svsp->bank_max; idx++) {
>   		svsb = &svsp->banks[idx];
>   
> @@ -1590,7 +1624,7 @@ static int svs_suspend(struct device *dev)
>   		return ret;
>   	}
>   
> -	clk_disable_unprepare(svsp->main_clk);
> +	svs_clk_disable(svsp);
>   
>   	return 0;
>   }
> @@ -1600,16 +1634,14 @@ static int svs_resume(struct device *dev)
>   	struct svs_platform *svsp = dev_get_drvdata(dev);
>   	int ret;
>   
> -	ret = clk_prepare_enable(svsp->main_clk);
> -	if (ret) {
> -		dev_err(svsp->dev, "cannot enable main_clk, disable svs\n");
> +	ret = svs_clk_enable(svsp);
> +	if (ret)
>   		return ret;
> -	}
>   
>   	ret = reset_control_deassert(svsp->rst);
>   	if (ret) {
>   		dev_err(svsp->dev, "cannot deassert reset %d\n", ret);
> -		goto out_of_resume;
> +		goto svs_resume_clk_disable;
>   	}
>   
>   	ret = svs_init02(svsp);
> @@ -1624,8 +1656,9 @@ static int svs_resume(struct device *dev)
>   	dev_err(svsp->dev, "assert reset: %d\n",
>   		reset_control_assert(svsp->rst));
>   
> -out_of_resume:
> -	clk_disable_unprepare(svsp->main_clk);
> +svs_resume_clk_disable:
> +	svs_clk_disable(svsp);
> +
>   	return ret;
>   }
>   
> @@ -2411,11 +2444,9 @@ static int svs_probe(struct platform_device *pdev)
>   		goto svs_probe_free_resource;
>   	}
>   
> -	ret = clk_prepare_enable(svsp->main_clk);
> -	if (ret) {
> -		dev_err(svsp->dev, "cannot enable main clk: %d\n", ret);
> +	ret = svs_clk_enable(svsp);
> +	if (ret)
>   		goto svs_probe_free_resource;
> -	}
>   
>   	svsp->base = of_iomap(svsp->dev->of_node, 0);
>   	if (IS_ERR_OR_NULL(svsp->base)) {
> @@ -2456,7 +2487,7 @@ static int svs_probe(struct platform_device *pdev)
>   	iounmap(svsp->base);
>   
>   svs_probe_clk_disable:
> -	clk_disable_unprepare(svsp->main_clk);
> +	svs_clk_disable(svsp);
>   
>   svs_probe_free_resource:
>   	if (!IS_ERR_OR_NULL(svsp->efuse))