linux-kernel - Re: [PATCH v1] clk: qcom: lpass: Add CLK_IGNORE

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Message-ID: <20190213071713.GI31919@minitux>
Date:   Tue, 12 Feb 2019 23:17:13 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Taniya Das <tdas@...eaurora.org>
Cc:     Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        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: [PATCH v1] clk: qcom: lpass: Add CLK_IGNORE_UNUSED for lpass
 clocks

On Thu 20 Dec 03:46 PST 2018, Taniya Das wrote:

> The LPASS clocks has a dependency on the GCC lpass clocks to be enabled
> before accessing them and that was the reason to mark the gcc lpass clocks
> as critical.

I have the same problem with the TuringCC in QCS404, that in order to
disable the unused clocks GCC_CDSP_CFG_AHB_CLK must be on. But rather
than marking either side as critical or ignore-unused I think a better
solution is to describe this dependency by using the fact that the clock
framework wraps any accesses in pm_runtime_get()/put() calls. So we can
use this to link the clock controller to some resources that needs to be
turned on whenever we communicate with it.

> But in the case where the lpass subsystem would require a
> restart, toggling the lpass reset would from HW clear the SW enable bits
> of the GCC lpass clocks. Thus the next time bringing up the lpass subsystem
> out of reset would fail.

Are you saying that when we toggle AOSS_CC_LPASS_RESTART the enable bit
is cleared on all these clocks and we might get out of sync between the
clock framework and the hardware?

Can you please elaborate a little bit on this? Afaict in the remoteproc
driver at least, we first disable the clock then we issue the reset.

Regards,
Bjorn

> 
> Allow the lpass clock driver to enable/disable the gcc lpass clocks and
> mark the lpass clocks not be accessed during late_init if no client vote.
> 
> Signed-off-by: Taniya Das <tdas@...eaurora.org>
> ---
>  drivers/clk/qcom/gcc-sdm845.c     | 2 --
>  drivers/clk/qcom/lpasscc-sdm845.c | 5 +++++
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/qcom/gcc-sdm845.c b/drivers/clk/qcom/gcc-sdm845.c
> index c782e62..8365c97 100644
> --- a/drivers/clk/qcom/gcc-sdm845.c
> +++ b/drivers/clk/qcom/gcc-sdm845.c
> @@ -3163,7 +3163,6 @@ enum {
>  		.enable_mask = BIT(0),
>  		.hw.init = &(struct clk_init_data){
>  			.name = "gcc_lpass_q6_axi_clk",
> -			.flags = CLK_IS_CRITICAL,
>  			.ops = &clk_branch2_ops,
>  		},
>  	},
> @@ -3177,7 +3176,6 @@ enum {
>  		.enable_mask = BIT(0),
>  		.hw.init = &(struct clk_init_data){
>  			.name = "gcc_lpass_sway_clk",
> -			.flags = CLK_IS_CRITICAL,
>  			.ops = &clk_branch2_ops,
>  		},
>  	},
> diff --git a/drivers/clk/qcom/lpasscc-sdm845.c b/drivers/clk/qcom/lpasscc-sdm845.c
> index e246b99..1acc741 100644
> --- a/drivers/clk/qcom/lpasscc-sdm845.c
> +++ b/drivers/clk/qcom/lpasscc-sdm845.c
> @@ -22,6 +22,7 @@
>  		.enable_mask = BIT(0),
>  		.hw.init = &(struct clk_init_data){
>  			.name = "lpass_q6ss_ahbm_aon_clk",
> +			.flags = CLK_IGNORE_UNUSED,
>  			.ops = &clk_branch2_ops,
>  		},
>  	},
> @@ -35,6 +36,7 @@
>  		.enable_mask = BIT(0),
>  		.hw.init = &(struct clk_init_data){
>  			.name = "lpass_q6ss_ahbs_aon_clk",
> +			.flags = CLK_IGNORE_UNUSED,
>  			.ops = &clk_branch2_ops,
>  		},
>  	},
> @@ -49,6 +51,7 @@
>  		.enable_mask = BIT(0),
>  		.hw.init = &(struct clk_init_data){
>  			.name = "lpass_qdsp6ss_core_clk",
> +			.flags = CLK_IGNORE_UNUSED,
>  			.ops = &clk_branch2_ops,
>  		},
>  	},
> @@ -63,6 +66,7 @@
>  		.enable_mask = BIT(0),
>  		.hw.init = &(struct clk_init_data){
>  			.name = "lpass_qdsp6ss_xo_clk",
> +			.flags = CLK_IGNORE_UNUSED,
>  			.ops = &clk_branch2_ops,
>  		},
>  	},
> @@ -77,6 +81,7 @@
>  		.enable_mask = BIT(0),
>  		.hw.init = &(struct clk_init_data){
>  			.name = "lpass_qdsp6ss_sleep_clk",
> +			.flags = CLK_IGNORE_UNUSED,
>  			.ops = &clk_branch2_ops,
>  		},
>  	},
> --
> Qualcomm INDIA, on behalf of Qualcomm Innovation Center, Inc.is a member
> of the Code Aurora Forum, hosted by the  Linux Foundation.
>