linux-kernel - Re: [PATCH V8 2/9] drivers core: add ACPI based WBRF mechanism introduced by AMD

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Message-ID: <ZNYBYuUSaio66vLN@vergenet.net>
Date:   Fri, 11 Aug 2023 11:37:38 +0200
From:   Simon Horman <horms@...nel.org>
To:     Evan Quan <evan.quan@....com>
Cc:     rafael@...nel.org, lenb@...nel.org, Alexander.Deucher@....com,
        Christian.Koenig@....com, Xinhui.Pan@....com, airlied@...il.com,
        daniel@...ll.ch, johannes@...solutions.net, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        Mario.Limonciello@....com, mdaenzer@...hat.com,
        maarten.lankhorst@...ux.intel.com, tzimmermann@...e.de,
        hdegoede@...hat.com, jingyuwang_vip@....com, Lijo.Lazar@....com,
        jim.cromie@...il.com, bellosilicio@...il.com,
        andrealmeid@...lia.com, trix@...hat.com, jsg@....id.au,
        arnd@...db.de, andrew@...n.ch, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH V8 2/9] drivers core: add ACPI based WBRF mechanism
 introduced by AMD

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@....com>
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> Co-developed-by: Evan Quan <evan.quan@....com>
> Signed-off-by: Evan Quan <evan.quan@....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;
> +}

...