linux-kernel - Re: [PATCH RFT v2 09/14] clk: qcom: smd-rpm: Add support for keepalive votes

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Date:   Thu, 9 Mar 2023 02:54:36 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        devicetree@...r.kernel.org, Shawn Guo <shawn.guo@...aro.org>,
        Taniya Das <quic_tdas@...cinc.com>
Subject: Re: [PATCH RFT v2 09/14] clk: qcom: smd-rpm: Add support for
 keepalive votes

On 08/03/2023 23:35, Konrad Dybcio wrote:
> Some bus clock should always have a minimum (19.2 MHz) vote cast on
> them, otherwise the platform will fall apart, hang and reboot.
> 
> Add support for specifying which clocks should be kept alive and
> always keep a vote on XO_A to make sure the clock tree doesn't
> collapse. This removes the need to keep a maximum vote that was
> previously guaranteed by clk_smd_rpm_handoff.
> 
> This commit is a combination of existing (not-exactly-upstream) work
> by Taniya Das, Shawn Guo and myself.
> 
> Co-developed-by: Shawn Guo <shawn.guo@...aro.org>
> Co-developed-by: Taniya Das <quic_tdas@...cinc.com>
> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> ---
>   drivers/clk/qcom/clk-smd-rpm.c | 29 +++++++++++++++++++++++++++--
>   1 file changed, 27 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/qcom/clk-smd-rpm.c b/drivers/clk/qcom/clk-smd-rpm.c
> index eb7781e5c8c1..d89918f9ae60 100644
> --- a/drivers/clk/qcom/clk-smd-rpm.c
> +++ b/drivers/clk/qcom/clk-smd-rpm.c
> @@ -45,15 +45,17 @@
>   		},							      \
>   	};								      \
>   	__DEFINE_CLK_SMD_RPM_AO_PREFIX(_prefix, _name, _active, type,	      \
> -				       r_id, key, ao_flags)
> +				       r_id, key, ao_flags, false)
>   
>   #define __DEFINE_CLK_SMD_RPM_AO_PREFIX(_prefix, _name, _active,		      \
> -				       type, r_id, key, ao_flags)	      \
> +				       type, r_id, key, ao_flags,	      \
> +				       _keep_alive)			      \
>   	static struct clk_smd_rpm clk_smd_rpm_##_prefix##_active = {	      \
>   		.rpm_res_type = (type),					      \
>   		.rpm_clk_id = (r_id),					      \
>   		.active_only = true,					      \
>   		.rpm_key = (key),					      \
> +		.keep_alive = (_keep_alive),				      \
>   		.peer = &clk_smd_rpm_##_prefix##_name,			      \
>   		.rate = INT_MAX,					      \
>   		.hw.init = &(struct clk_init_data){			      \
> @@ -170,6 +172,7 @@ struct clk_smd_rpm {
>   	const bool active_only;
>   	bool enabled;
>   	bool branch;
> +	bool keep_alive;
>   	struct clk_smd_rpm *peer;
>   	struct clk_hw hw;
>   	unsigned long rate;
> @@ -198,11 +201,16 @@ static int clk_smd_rpm_handoff(struct clk_smd_rpm *r)
>   		.value = cpu_to_le32(r->branch ? 1 : INT_MAX),
>   	};
>   
> +	/* Set up keepalive clocks with a minimum bus rate */
> +	if (r->keep_alive)
> +		req.value = cpu_to_le32(19200); /* 19.2 MHz */


Should this be set to cpu_to_le32(max(19200, ...)) ?

> +
>   	ret = qcom_rpm_smd_write(r->rpm, QCOM_SMD_RPM_ACTIVE_STATE,
>   				 r->rpm_res_type, r->rpm_clk_id, &req,
>   				 sizeof(req));
>   	if (ret)
>   		return ret;
> +
>   	ret = qcom_rpm_smd_write(r->rpm, QCOM_SMD_RPM_SLEEP_STATE,
>   				 r->rpm_res_type, r->rpm_clk_id, &req,
>   				 sizeof(req));
> @@ -438,12 +446,29 @@ static int clk_smd_rpm_is_enabled(struct clk_hw *hw)
>   	return r->enabled;
>   }
>   
> +static int clk_smd_rpm_determine_rate(struct clk_hw *hw,
> +				      struct clk_rate_request *req)
> +{
> +	struct clk_smd_rpm *r = to_clk_smd_rpm(hw);
> +
> +	/*
> +	 * RPM resolves the rates internally. All we have to do on the kernel
> +	 * side is ensure that we don't accidentally put down the keepalive
> +	 * clocks, which could happen if they received a vote below 19.2 MHz.
> +	 */
> +	if (r->keep_alive)
> +		req->rate = max(req->rate, 19200000UL);
> +
> +	return 0;
> +}
> +
>   static const struct clk_ops clk_smd_rpm_ops = {
>   	.prepare	= clk_smd_rpm_prepare,
>   	.unprepare	= clk_smd_rpm_unprepare,
>   	.set_rate	= clk_smd_rpm_set_rate,
>   	.round_rate	= clk_smd_rpm_round_rate,
>   	.recalc_rate	= clk_smd_rpm_recalc_rate,
> +	.determine_rate = clk_smd_rpm_determine_rate,
>   	.is_enabled	= clk_smd_rpm_is_enabled,
>   	.is_prepared	= clk_smd_rpm_is_enabled,
>   };
> 

-- 
With best wishes
Dmitry