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Date:   Fri, 11 Aug 2023 11:37:38 +0200
From:   Simon Horman <horms@kernel.org>
To:     Evan Quan <evan.quan@amd.com>
Cc:     rafael@kernel.org, lenb@kernel.org, Alexander.Deucher@amd.com,
        Christian.Koenig@amd.com, Xinhui.Pan@amd.com, airlied@gmail.com,
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        Mario.Limonciello@amd.com, mdaenzer@redhat.com,
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Subject: Re: [PATCH V8 2/9] drivers core: add ACPI based WBRF mechanism
 introduced by AMD
Message-ID: <ZNYBYuUSaio66vLN@vergenet.net>
References: <20230810073803.1643451-1-evan.quan@amd.com>
 <20230810073803.1643451-3-evan.quan@amd.com>
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In-Reply-To: <20230810073803.1643451-3-evan.quan@amd.com>
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On Thu, Aug 10, 2023 at 03:37:56PM +0800, Evan Quan wrote:
> AMD has introduced an ACPI based mechanism to support WBRF for some
> platforms with AMD dGPU + WLAN. This needs support from BIOS equipped
> with necessary AML implementations and dGPU firmwares.
> 
> For those systems without the ACPI mechanism and developing solutions,
> user can use/fall-back the generic WBRF solution for diagnosing potential
> interference issues.
> 
> And for the platform which does not equip with the necessary AMD ACPI
> implementations but with CONFIG_WBRF_AMD_ACPI built as 'y', it will
> fall back to generic WBRF solution if the `wbrf` is set as "on".
> 
> Co-developed-by: Mario Limonciello <mario.limonciello@amd.com>
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> Co-developed-by: Evan Quan <evan.quan@amd.com>
> Signed-off-by: Evan Quan <evan.quan@amd.com>

...

> diff --git a/drivers/acpi/amd_wbrf.c b/drivers/acpi/amd_wbrf.c

...

> +static bool check_acpi_wbrf(acpi_handle handle, u64 rev, u64 funcs)
> +{
> +	int i;
> +	u64 mask = 0;
> +	union acpi_object *obj;
> +
> +	if (funcs == 0)
> +		return false;
> +
> +	obj = acpi_evaluate_wbrf(handle, rev, 0);
> +	if (!obj)
> +		return false;
> +
> +	if (obj->type != ACPI_TYPE_BUFFER)
> +		return false;
> +
> +	/*
> +	 * Bit vector providing supported functions information.
> +	 * Each bit marks support for one specific function of the WBRF method.
> +	 */
> +	for (i = 0; i < obj->buffer.length && i < 8; i++)
> +		mask |= (((u64)obj->buffer.pointer[i]) << (i * 8));
> +
> +	ACPI_FREE(obj);
> +
> +	if ((mask & BIT(WBRF_ENABLED)) &&
> +	     (mask & funcs) == funcs)

Hi Evan,

a minor nit from my side: the indentation of the line above seems odd.

	if ((mask & BIT(WBRF_ENABLED)) &&
	    (mask & funcs) == funcs)

> +		return true;
> +
> +	return false;
> +}

...