linux-kernel - Re: [PATCH v7 03/10] accel/rocket: Add IOCTL for BO creation

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Message-ID: <8888010.K2JlShyGXD@diego>
Date: Tue, 01 Jul 2025 21:31:59 +0200
From: Heiko Stübner <heiko@...ech.de>
To: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Oded Gabbay <ogabbay@...nel.org>,
 Jonathan Corbet <corbet@....net>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Sumit Semwal <sumit.semwal@...aro.org>,
 Christian König <christian.koenig@....com>,
 Sebastian Reichel <sebastian.reichel@...labora.com>,
 Nicolas Frattaroli <nicolas.frattaroli@...labora.com>,
 Kever Yang <kever.yang@...k-chips.com>, Robin Murphy <robin.murphy@....com>,
 Daniel Stone <daniel@...ishbar.org>, Da Xue <da@...re.computer>,
 Jeff Hugo <jeff.hugo@....qualcomm.com>, Tomeu Vizoso <tomeu@...euvizoso.net>
Cc: devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, linux-doc@...r.kernel.org,
 linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org,
 Tomeu Vizoso <tomeu@...euvizoso.net>
Subject: Re: [PATCH v7 03/10] accel/rocket: Add IOCTL for BO creation

Am Freitag, 6. Juni 2025, 08:28:23 Mitteleuropäische Sommerzeit schrieb Tomeu Vizoso:
> This uses the SHMEM DRM helpers and we map right away to the CPU and NPU
> sides, as all buffers are expected to be accessed from both.
> 
> v2:
> - Sync the IOMMUs for the other cores when mapping and unmapping.
> 
> v3:
> - Make use of GPL-2.0-only for the copyright notice (Jeff Hugo)
> 
> v6:
> - Use mutexes guard (Markus Elfring)
> 
> v7:
> - Assign its own IOMMU domain to each client, for isolation (Daniel
>   Stone and Robin Murphy)
> 
> Reviewed-by: Jeffrey Hugo <quic_jhugo@...cinc.com>
> Signed-off-by: Tomeu Vizoso <tomeu@...euvizoso.net>
> ---

> diff --git a/drivers/accel/rocket/rocket_gem.c b/drivers/accel/rocket/rocket_gem.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..61b7f970a6885aa13784daa1222611a02aa10dee
> --- /dev/null
> +++ b/drivers/accel/rocket/rocket_gem.c
> @@ -0,0 +1,115 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Copyright 2024-2025 Tomeu Vizoso <tomeu@...euvizoso.net> */
> +
> +#include <drm/drm_device.h>
> +#include <drm/drm_utils.h>
> +#include <drm/rocket_accel.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/iommu.h>
> +
> +#include "rocket_device.h"
> +#include "rocket_drv.h"
> +#include "rocket_gem.h"
> +
> +static void rocket_gem_bo_free(struct drm_gem_object *obj)
> +{
> +	struct rocket_device *rdev = to_rocket_device(obj->dev);
> +	struct rocket_gem_object *bo = to_rocket_bo(obj);
> +	size_t unmapped;
> +
> +	drm_WARN_ON(obj->dev, bo->base.pages_use_count > 1);

This should probably be
    drm_WARN_ON(obj->dev, refcount_read(&bo->base.pages_use_count) > 1);

as pages_use_count is of type refcount_t since
commit 051b6646d36d ("drm/shmem-helper: Use refcount_t for pages_use_count")

Heiko