linux-kernel - Re: [PATCH v2 1/6] acpi: cppc: Add min and max perf reg writing support

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Message-ID: <85925bce-f30a-b2df-309f-bd4b510a117c@amd.com>
Date:   Thu, 12 Jan 2023 23:37:03 -0600
From:   Mario Limonciello <mario.limonciello@....com>
To:     Wyes Karny <wyes.karny@....com>,
        Rafael J Wysocki <rafael@...nel.org>,
        Huang Rui <ray.huang@....com>,
        Jonathan Corbet <corbet@....net>,
        Viresh Kumar <viresh.kumar@...aro.org>, Perry.Yuan@....com,
        Ananth Narayan <ananth.narayan@....com>, gautham.shenoy@....com
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, Bagas Sanjaya <bagasdotme@...il.com>,
        santosh.shukla@....com
Subject: Re: [PATCH v2 1/6] acpi: cppc: Add min and max perf reg writing
 support

On 1/12/23 23:21, Wyes Karny wrote:
> Currently writing of min and max perf register is deferred in
> cppc_set_perf function. In CPPC guided mode, these registers needed to
> be written to guide PMFW about min and max perf levels. Add this support

This is generic code, so  I think rather than PMFW you should just say 
"the platform".

> to make guided mode work properly on shared memory systems.

on AMD shared memory systems.

> 
> Signed-off-by: Wyes Karny <wyes.karny@....com>

With the commit message cleaned up:

Reviewed-by: Mario Limonciello <mario.limonciello@....com>
> ---
>   drivers/acpi/cppc_acpi.c | 16 ++++++++--------
>   1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> index 02d83c807271..c936ff503965 100644
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -1487,7 +1487,7 @@ EXPORT_SYMBOL_GPL(cppc_set_enable);
>   int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
>   {
>   	struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
> -	struct cpc_register_resource *desired_reg;
> +	struct cpc_register_resource *desired_reg, *min_perf_reg, *max_perf_reg;
>   	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
>   	struct cppc_pcc_data *pcc_ss_data = NULL;
>   	int ret = 0;
> @@ -1498,6 +1498,8 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
>   	}
>   
>   	desired_reg = &cpc_desc->cpc_regs[DESIRED_PERF];
> +	min_perf_reg = &cpc_desc->cpc_regs[MIN_PERF];
> +	max_perf_reg = &cpc_desc->cpc_regs[MAX_PERF];
>   
>   	/*
>   	 * This is Phase-I where we want to write to CPC registers
> @@ -1506,7 +1508,7 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
>   	 * Since read_lock can be acquired by multiple CPUs simultaneously we
>   	 * achieve that goal here
>   	 */
> -	if (CPC_IN_PCC(desired_reg)) {
> +	if (CPC_IN_PCC(desired_reg) || CPC_IN_PCC(min_perf_reg) || CPC_IN_PCC(max_perf_reg)) {
>   		if (pcc_ss_id < 0) {
>   			pr_debug("Invalid pcc_ss_id\n");
>   			return -ENODEV;
> @@ -1529,13 +1531,11 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
>   		cpc_desc->write_cmd_status = 0;
>   	}
>   
> -	/*
> -	 * Skip writing MIN/MAX until Linux knows how to come up with
> -	 * useful values.
> -	 */
>   	cpc_write(cpu, desired_reg, perf_ctrls->desired_perf);
> +	cpc_write(cpu, min_perf_reg, perf_ctrls->min_perf);
> +	cpc_write(cpu, max_perf_reg, perf_ctrls->max_perf);
>   
> -	if (CPC_IN_PCC(desired_reg))
> +	if (CPC_IN_PCC(desired_reg) || CPC_IN_PCC(min_perf_reg) || CPC_IN_PCC(max_perf_reg))
>   		up_read(&pcc_ss_data->pcc_lock);	/* END Phase-I */
>   	/*
>   	 * This is Phase-II where we transfer the ownership of PCC to Platform
> @@ -1583,7 +1583,7 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
>   	 * case during a CMD_READ and if there are pending writes it delivers
>   	 * the write command before servicing the read command
>   	 */
> -	if (CPC_IN_PCC(desired_reg)) {
> +	if (CPC_IN_PCC(desired_reg) || CPC_IN_PCC(min_perf_reg) || CPC_IN_PCC(max_perf_reg)) {
>   		if (down_write_trylock(&pcc_ss_data->pcc_lock)) {/* BEGIN Phase-II */
>   			/* Update only if there are pending write commands */
>   			if (pcc_ss_data->pending_pcc_write_cmd)