linux-kernel - Re: [PATCH 5/6] acpi/cppc: Add support for optional CPPC registers

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Date:   Wed, 27 Mar 2019 15:47:59 +0000
From:   "Pandruvada, Srinivas" <srinivas.pandruvada@...el.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devel@...ica.org" <devel@...ica.org>,
        "Janakarajan.Natarajan@....com" <Janakarajan.Natarajan@....com>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
CC:     "Yazen.Ghannam@....com" <Yazen.Ghannam@....com>,
        "lenb@...nel.org" <lenb@...nel.org>,
        "viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
        "Moore, Robert" <robert.moore@...el.com>,
        "Schmauss, Erik" <erik.schmauss@...el.com>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>
Subject: Re: [PATCH 5/6] acpi/cppc: Add support for optional CPPC registers

On Fri, 2019-03-22 at 20:26 +0000, Natarajan, Janakarajan wrote:
> From: Yazen Ghannam <Yazen.Ghannam@....com>
> 
> Newer AMD processors support a subset of the optional CPPC registers.
> Create show, store and helper routines for supported CPPC registers.
> 
> Signed-off-by: Yazen Ghannam <Yazen.Ghannam@....com>
> [ carved out into a patch, cleaned up, productized ]
> Signed-off-by: Janakarajan Natarajan <Janakarajan.Natarajan@....com>
> 

[..]

> +	/* desired_perf is the only mandatory value in perf_ctrls */
> +	if (cpc_read(cpu, desired_reg, &desired))
> +		ret = -EFAULT;
> +
> +	if (CPC_SUPPORTED(max_reg) && cpc_read(cpu, max_reg, &max))
> +		ret = -EFAULT;
> +
We should create and use different macro other than CPPC_SUPPORTED.
CPC_SUPPORTED doesn't validate the correctness of object type for a
field. For example "Maximum Performance Register" can only be buffer
not integer. In this way invalid field definitions can be ignored.


> +	if (CPC_SUPPORTED(min_reg) && cpc_read(cpu, min_reg, &min))
> +		ret = -EFAULT;
> +
> +	if (CPC_SUPPORTED(energy_reg) && cpc_read(cpu, energy_reg,
> &energy))
> +		ret = -EFAULT;
> +
> +	if (CPC_SUPPORTED(auto_sel_enable_reg) &&
> +	    cpc_read(cpu, auto_sel_enable_reg, &auto_sel_enable))
> +		ret = -EFAULT;
> +
Here it is fine to use CPC_SUPPORTED as the "Autonomous Selection
Enable" can be both integer and buffer.

Thanks,
Srinivas


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