linux-kernel - Re: [PATCH v2 2/4] media: rockchip: Introduce the rkvdec2 driver

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Date: Thu, 20 Jun 2024 12:30:00 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Detlev Casanova <detlev.casanova@...labora.com>,
 linux-kernel@...r.kernel.org
Cc: Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
 Mauro Carvalho Chehab <mchehab@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Heiko Stuebner <heiko@...ech.de>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Sebastian Reichel <sebastian.reichel@...labora.com>,
 Dragan Simic <dsimic@...jaro.org>, Diederik de Haas <didi.debian@...ow.org>,
 Andy Yan <andy.yan@...k-chips.com>,
 Boris Brezillon <boris.brezillon@...labora.com>,
 Hans Verkuil <hverkuil-cisco@...all.nl>,
 Daniel Almeida <daniel.almeida@...labora.com>,
 Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
 Nicolas Dufresne <nicolas.dufresne@...labora.com>,
 Benjamin Gaignard <benjamin.gaignard@...labora.com>,
 Jonas Karlman <jonas@...boo.se>, Alex Bee <knaerzche@...il.com>,
 linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-staging@...ts.linux.dev
Subject: Re: [PATCH v2 2/4] media: rockchip: Introduce the rkvdec2 driver

On 19/06/2024 16:57, Detlev Casanova wrote:
> +static const char * const rkvdec2_clk_names[] = {
> +	"axi",
> +	"ahb",
> +	"core",
> +	"cabac",
> +	"hevc_cabac",
> +};
> +
> +/*
> + * Some SoCs, like RK3588 have multiple identical vdpu34x cores, but the
> + * kernel is currently missing support for multi-core handling. Exposing
> + * separate devices for each core to userspace is bad, since that does
> + * not allow scheduling tasks properly (and creates ABI). With this workaround
> + * the driver will only probe for the first core and early exit for the other
> + * cores. Once the driver gains multi-core support, the same technique
> + * for detecting the main core can be used to cluster all cores together.
> + */
> +static int rkvdec2_disable_multicore(struct rkvdec2_dev *rkvdec)
> +{
> +	const char *compatible;
> +	struct device_node *node;
> +	int ret;
> +
> +	/* Intentionally ignores the fallback strings */
> +	ret = of_property_read_string(rkvdec->dev->of_node, "compatible", &compatible);
> +	if (ret)
> +		return ret;
> +
> +	/* first compatible node found from the root node is considered the main core */

So you rely on order of nodes? Before you claim "identical cores", but
now "main core" suggests one is different than others.

...

Best regards,
Krzysztof