linux-kernel - Re: [PATCH v3] clk: qcom: gdsc: Add a flag to skip setting power collapse bits

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Message-ID: <sfnqygr6rodqidyjo2ighia4pvjhavm4nuijrx7pi62pel7qur@ycpn7qjgnybv>
Date: Tue, 7 Jan 2025 11:49:57 -0600
From: Bjorn Andersson <andersson@...nel.org>
To: Georgi Djakov <quic_c_gdjako@...cinc.com>
Cc: sboyd@...nel.org, mturquette@...libre.com, quic_mdtipton@...cinc.com, 
	linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org, 
	djakov@...nel.org
Subject: Re: [PATCH v3] clk: qcom: gdsc: Add a flag to skip setting power
 collapse bits

On Thu, Dec 05, 2024 at 02:21:56PM -0800, Georgi Djakov wrote:
> The sdm845 platforms have a hardware issue that requires keeping
> some of the MMNOC GDSCs in SW collapse mode (which is the power-on

Here you say "keep in SW collapse".

> default). But if some driver tries to use these GDSCs and the mode
> is updated because of runtime pm calls, we may get a board hang.
> Introduce a flag to skip any updates to the power collapse settings
> for the impacted GDSCs to avoid unexpected board hangs.
> 
> Fixes: 7bb38c20f2b6 ("arm64: dts: qcom: sdm845: Add DT nodes for the TBUs")
> Reviewed-by: Mike Tipton <quic_mdtipton@...cinc.com>
> Signed-off-by: Georgi Djakov <quic_c_gdjako@...cinc.com>
> ---
> v3:
> - No changes
> 
> v2: https://lore.kernel.org/r/20241009151657.1041691-1-quic_c_gdjako@quicinc.com/
> - Pick up Reviewed-by tag
> - Add Fixes tag
> 
> v1: https://lore.kernel.org/r/20240813120015.3242787-1-quic_c_gdjako@quicinc.com/ 
>  drivers/clk/qcom/gcc-sdm845.c | 6 +++---
>  drivers/clk/qcom/gdsc.c       | 3 +++
>  drivers/clk/qcom/gdsc.h       | 1 +
>  3 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/clk/qcom/gcc-sdm845.c b/drivers/clk/qcom/gcc-sdm845.c
> index dc3aa7014c3e..019b780e31c8 100644
> --- a/drivers/clk/qcom/gcc-sdm845.c
> +++ b/drivers/clk/qcom/gcc-sdm845.c
> @@ -3503,7 +3503,7 @@ static struct gdsc hlos1_vote_mmnoc_mmu_tbu_hf0_gdsc = {
>  		.name = "hlos1_vote_mmnoc_mmu_tbu_hf0_gdsc",
>  	},
>  	.pwrsts = PWRSTS_OFF_ON,
> -	.flags = VOTABLE,
> +	.flags = VOTABLE | SKIP_SET_COLLAPSE,
>  };
>  
>  static struct gdsc hlos1_vote_mmnoc_mmu_tbu_hf1_gdsc = {
> @@ -3512,7 +3512,7 @@ static struct gdsc hlos1_vote_mmnoc_mmu_tbu_hf1_gdsc = {
>  		.name = "hlos1_vote_mmnoc_mmu_tbu_hf1_gdsc",
>  	},
>  	.pwrsts = PWRSTS_OFF_ON,
> -	.flags = VOTABLE,
> +	.flags = VOTABLE | SKIP_SET_COLLAPSE,
>  };
>  
>  static struct gdsc hlos1_vote_mmnoc_mmu_tbu_sf_gdsc = {
> @@ -3521,7 +3521,7 @@ static struct gdsc hlos1_vote_mmnoc_mmu_tbu_sf_gdsc = {
>  		.name = "hlos1_vote_mmnoc_mmu_tbu_sf_gdsc",
>  	},
>  	.pwrsts = PWRSTS_OFF_ON,
> -	.flags = VOTABLE,
> +	.flags = VOTABLE | SKIP_SET_COLLAPSE,
>  };
>  
>  static struct clk_regmap *gcc_sdm670_clocks[] = {
> diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
> index fa5fe4c2a2ee..4b83cec9137c 100644
> --- a/drivers/clk/qcom/gdsc.c
> +++ b/drivers/clk/qcom/gdsc.c
> @@ -121,6 +121,9 @@ static int gdsc_update_collapse_bit(struct gdsc *sc, bool val)
>  	u32 reg, mask;
>  	int ret;
>  
> +	if (sc->flags & SKIP_SET_COLLAPSE)
> +		return 0;

And here you say "skip SW collapse" (well functionally you say skip set
or clear SW collapse, but the constant says "skip set/enter SW collapse").


Do you need to perform the other functions of gdsc_enable() and
gdsc_disable() for these GDSCs?

Is there a reason why we declare PWRSTS_ON and PWRSTS_OFF as valid
states for this GDSCs and then add a quirk/hack at the bottom of the
callstack to not perform the (key) operation?

Regards,
Bjorn

> +
>  	if (sc->collapse_mask) {
>  		reg = sc->collapse_ctrl;
>  		mask = sc->collapse_mask;
> diff --git a/drivers/clk/qcom/gdsc.h b/drivers/clk/qcom/gdsc.h
> index 1e2779b823d1..6bb7e023a19a 100644
> --- a/drivers/clk/qcom/gdsc.h
> +++ b/drivers/clk/qcom/gdsc.h
> @@ -68,6 +68,7 @@ struct gdsc {
>  #define RETAIN_FF_ENABLE	BIT(7)
>  #define NO_RET_PERIPH	BIT(8)
>  #define HW_CTRL_TRIGGER	BIT(9)
> +#define SKIP_SET_COLLAPSE	BIT(10)
>  	struct reset_controller_dev	*rcdev;
>  	unsigned int			*resets;
>  	unsigned int			reset_count;