linux-kernel - Re: [PATCH V6 3/5] clk: qcom: gdsc: Add set and get hwmode callbacks to switch GDSC mode

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Message-ID: <18c0b683-97c8-4d53-9852-840a21c11d9a@linaro.org>
Date: Thu, 20 Jun 2024 00:10:31 +0200
From: Caleb Connolly <caleb.connolly@...aro.org>
To: Jagadeesh Kona <quic_jkona@...cinc.com>,
 Bjorn Andersson <andersson@...nel.org>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Stanimir Varbanov <stanimir.k.varbanov@...il.com>,
 Vikash Garodia <quic_vgarodia@...cinc.com>,
 Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
 Mauro Carvalho Chehab <mchehab@...nel.org>,
 Ulf Hansson <ulf.hansson@...aro.org>, "Rafael J . Wysocki"
 <rafael@...nel.org>, Kevin Hilman <khilman@...nel.org>,
 Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Konrad Dybcio <konrad.dybcio@...aro.org>, Andy Gross <agross@...nel.org>,
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 Abel Vesa <abel.vesa@...aro.org>
Cc: linux-pm@...r.kernel.org, linux-media@...r.kernel.org,
 linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
 linux-kernel@...r.kernel.org, Taniya Das <quic_tdas@...cinc.com>,
 Satya Priya Kakitapalli <quic_skakitap@...cinc.com>,
 Imran Shaik <quic_imrashai@...cinc.com>,
 Ajit Pandey <quic_ajipan@...cinc.com>
Subject: Re: [PATCH V6 3/5] clk: qcom: gdsc: Add set and get hwmode callbacks
 to switch GDSC mode

Hi Jagadeesh,

Sorry, some grammar nitpicks.

On 19/06/2024 16:14, Jagadeesh Kona wrote:
> Some GDSC client drivers require the GDSC mode to be switched dynamically
> to HW mode at runtime to gain the power benefits. Typically such client
> drivers require the GDSC to be brought up in SW mode initially to enable
> the required dependent clocks and configure the hardware to proper state.
> Once initial hardware set up is done, they switch the GDSC to HW mode to
> save power. At the end of usecase, they switch the GDSC back to SW mode
> and disable the GDSC.
> 
> Introduce HW_CTRL_TRIGGER flag to register the set_hwmode_dev and
> get_hwmode_dev callbacks for GDSC's whose respective client drivers
> require the GDSC mode to be switched dynamically at runtime using
> dev_pm_genpd_set_hwmode() API.
> 
> Signed-off-by: Jagadeesh Kona <quic_jkona@...cinc.com>
> Signed-off-by: Abel Vesa <abel.vesa@...aro.org>
> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
> ---
>   drivers/clk/qcom/gdsc.c | 42 +++++++++++++++++++++++++++++++++++++++++
>   drivers/clk/qcom/gdsc.h |  1 +
>   2 files changed, 43 insertions(+)
> 
> diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
> index df9618ab7eea..6acc7af82255 100644
> --- a/drivers/clk/qcom/gdsc.c
> +++ b/drivers/clk/qcom/gdsc.c
> @@ -363,6 +363,44 @@ static int gdsc_disable(struct generic_pm_domain *domain)
>   	return 0;
>   }
>   
> +static int gdsc_set_hwmode(struct generic_pm_domain *domain, struct device *dev, bool mode)
> +{
> +	struct gdsc *sc = domain_to_gdsc(domain);
> +	int ret;
> +
> +	ret = gdsc_hwctrl(sc, mode);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * Wait for the GDSC to go through a power down and
> +	 * up cycle. In case SW/FW end up polling status
> +	 * bits for the gdsc before the power cycle is completed
> +	 * it might read the status wrongly.

If we poll the status register before the power cycle is finished we 
might read incorrect values.
> +	 */
> +	udelay(1);
> +
> +	/*
> +	 * When GDSC is switched to HW mode, HW can disable the GDSC.
The GDSC
> +	 * When GDSC is switched back to SW mode, the GDSC will be enabled
The GDSC
> +	 * again, hence need to poll for GDSC to complete the power uphence we need to poll

Kind regards,
> +	 */
> +	if (!mode)
> +		return gdsc_poll_status(sc, GDSC_ON);
> +
> +	return 0;
> +}
> +
> +static bool gdsc_get_hwmode(struct generic_pm_domain *domain, struct device *dev)
> +{
> +	struct gdsc *sc = domain_to_gdsc(domain);
> +	u32 val;
> +
> +	regmap_read(sc->regmap, sc->gdscr, &val);
> +
> +	return !!(val & HW_CONTROL_MASK);
> +}
> +
>   static int gdsc_init(struct gdsc *sc)
>   {
>   	u32 mask, val;
> @@ -451,6 +489,10 @@ static int gdsc_init(struct gdsc *sc)
>   		sc->pd.power_off = gdsc_disable;
>   	if (!sc->pd.power_on)
>   		sc->pd.power_on = gdsc_enable;
> +	if (sc->flags & HW_CTRL_TRIGGER) {
> +		sc->pd.set_hwmode_dev = gdsc_set_hwmode;
> +		sc->pd.get_hwmode_dev = gdsc_get_hwmode;
> +	}
>   
>   	ret = pm_genpd_init(&sc->pd, NULL, !on);
>   	if (ret)
> diff --git a/drivers/clk/qcom/gdsc.h b/drivers/clk/qcom/gdsc.h
> index 803512688336..1e2779b823d1 100644
> --- a/drivers/clk/qcom/gdsc.h
> +++ b/drivers/clk/qcom/gdsc.h
> @@ -67,6 +67,7 @@ struct gdsc {
>   #define ALWAYS_ON	BIT(6)
>   #define RETAIN_FF_ENABLE	BIT(7)
>   #define NO_RET_PERIPH	BIT(8)
> +#define HW_CTRL_TRIGGER	BIT(9)
>   	struct reset_controller_dev	*rcdev;
>   	unsigned int			*resets;
>   	unsigned int			reset_count;

-- 
// Caleb (they/them)