linux-kernel - Re: [v1 1/2] clk: qcom: gdsc: Use the default transition delay for GDSCs

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Message-ID: <YgQFu2CkBjx3O2i5@builder.lan>
Date:   Wed, 9 Feb 2022 12:19:39 -0600
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Taniya Das <tdas@...eaurora.org>
Cc:     Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette ? <mturquette@...libre.com>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [v1 1/2] clk: qcom: gdsc: Use the default transition delay for
 GDSCs

On Wed 09 Feb 11:25 CST 2022, Taniya Das wrote:

> Do not update the transition delay and use the default reset values.
> 

Can you help me understand what "the transition delay" is? In particular
I would like to know which other platforms, past, present and future
should have this flag set - or not set.

> Fixes: 45dd0e55317cc ("clk: qcom: Add support for GDSCs)
> Signed-off-by: Taniya Das <tdas@...eaurora.org>
> ---
>  drivers/clk/qcom/gdsc.c | 6 +++++-
>  drivers/clk/qcom/gdsc.h | 1 +
>  2 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
> index 7e1dd8ccfa38..e7b213450640 100644
> --- a/drivers/clk/qcom/gdsc.c
> +++ b/drivers/clk/qcom/gdsc.c
> @@ -380,7 +380,11 @@ static int gdsc_init(struct gdsc *sc)
>  	 */
>  	mask = HW_CONTROL_MASK | SW_OVERRIDE_MASK |
>  	       EN_REST_WAIT_MASK | EN_FEW_WAIT_MASK | CLK_DIS_WAIT_MASK;
> -	val = EN_REST_WAIT_VAL | EN_FEW_WAIT_VAL | CLK_DIS_WAIT_VAL;
> +
> +	regmap_read(sc->regmap, sc->gdscr, &val);
> +
> +	if (!(sc->flags & DEFAULT_TRANSITION_DELAY))

Why is it a good idea to not have a transition delay other than the
default one on all the other gdscs?

Regards,
Bjorn

> +		val |= EN_REST_WAIT_VAL | EN_FEW_WAIT_VAL | CLK_DIS_WAIT_VAL;
>  	ret = regmap_update_bits(sc->regmap, sc->gdscr, mask, val);
>  	if (ret)
>  		return ret;
> diff --git a/drivers/clk/qcom/gdsc.h b/drivers/clk/qcom/gdsc.h
> index d7cc4c21a9d4..1bd3ecdd0b0a 100644
> --- a/drivers/clk/qcom/gdsc.h
> +++ b/drivers/clk/qcom/gdsc.h
> @@ -53,6 +53,7 @@ struct gdsc {
>  #define ALWAYS_ON	BIT(6)
>  #define RETAIN_FF_ENABLE	BIT(7)
>  #define NO_RET_PERIPH	BIT(8)
> +#define DEFAULT_TRANSITION_DELAY	BIT(9)
>  	struct reset_controller_dev	*rcdev;
>  	unsigned int			*resets;
>  	unsigned int			reset_count;
> --
> Qualcomm INDIA, on behalf of Qualcomm Innovation Center, Inc.is a member
> of the Code Aurora Forum, hosted by the  Linux Foundation.
>