linux-kernel - [PATCH 5/5] accel/thames: Add IOCTL for memory synchronization

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Message-Id: <20260113-thames-v1-5-99390026937c@tomeuvizoso.net>
Date: Tue, 13 Jan 2026 18:44:39 +0100
From: Tomeu Vizoso <tomeu@...euvizoso.net>
To: Nishanth Menon <nm@...com>, "Andrew F. Davis" <afd@...com>, 
 Randolph Sapp <rs@...com>, Jonathan Humphreys <j-humphreys@...com>, 
 Andrei Aldea <a-aldea@...com>, Chirag Shilwant <c-shilwant@...com>, 
 Vignesh Raghavendra <vigneshr@...com>, Tero Kristo <kristo@...nel.org>, 
 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>, Sumit Semwal <sumit.semwal@...aro.org>, 
 Christian König <christian.koenig@....com>
Cc: linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.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: [PATCH 5/5] accel/thames: Add IOCTL for memory synchronization

The DSP cores have their own access to the memory bus, and it isn't
cache coherent with the CPUs.

Add IOCTLs so userspace can mark when the caches need to be flushed, and
also when a writer job needs to be waited for before the buffer can be
accessed from the CPU.

Initially based on the same IOCTLs from the Etnaviv driver.

Signed-off-by: Tomeu Vizoso <tomeu@...euvizoso.net>
---
 drivers/accel/thames/thames_drv.c |  2 ++
 drivers/accel/thames/thames_gem.c | 52 +++++++++++++++++++++++++++++++++++++++
 drivers/accel/thames/thames_gem.h |  4 +++
 3 files changed, 58 insertions(+)

diff --git a/drivers/accel/thames/thames_drv.c b/drivers/accel/thames/thames_drv.c
index bf7355832241d5a671e196f465d891effaa4a8fb..9b72db433fbb8f9239a16a047a52520f0a01d125 100644
--- a/drivers/accel/thames/thames_drv.c
+++ b/drivers/accel/thames/thames_drv.c
@@ -76,6 +76,8 @@ static const struct drm_ioctl_desc thames_drm_driver_ioctls[] = {
 	THAMES_IOCTL(BO_CREATE, bo_create),
 	THAMES_IOCTL(BO_MMAP_OFFSET, bo_mmap_offset),
 	THAMES_IOCTL(SUBMIT, submit),
+	THAMES_IOCTL(BO_PREP, bo_prep),
+	THAMES_IOCTL(BO_FINI, bo_fini),
 };
 
 DEFINE_DRM_ACCEL_FOPS(thames_accel_driver_fops);
diff --git a/drivers/accel/thames/thames_gem.c b/drivers/accel/thames/thames_gem.c
index a153e73a15253e0f955d74020b4765a1fa833fc4..2ad5a62bea275eb38a96b9d9bea804ed94ffb011 100644
--- a/drivers/accel/thames/thames_gem.c
+++ b/drivers/accel/thames/thames_gem.c
@@ -353,3 +353,55 @@ int thames_ioctl_bo_mmap_offset(struct drm_device *ddev, void *data, struct drm_
 
 	return 0;
 }
+
+int thames_ioctl_bo_prep(struct drm_device *ddev, void *data, struct drm_file *file)
+{
+	struct drm_thames_bo_prep *args = data;
+	struct drm_gem_object *gem_obj;
+	struct drm_gem_shmem_object *shmem_obj;
+	unsigned long timeout = drm_timeout_abs_to_jiffies(args->timeout_ns);
+	long ret = 0;
+
+	if (args->reserved != 0)
+		return -EINVAL;
+
+	gem_obj = drm_gem_object_lookup(file, args->handle);
+	if (!gem_obj)
+		return -ENOENT;
+
+	ret = dma_resv_wait_timeout(gem_obj->resv, DMA_RESV_USAGE_WRITE, true, timeout);
+	if (!ret)
+		ret = timeout ? -ETIMEDOUT : -EBUSY;
+
+	shmem_obj = &to_thames_bo(gem_obj)->base;
+
+	dma_sync_sgtable_for_cpu(ddev->dev, shmem_obj->sgt, DMA_FROM_DEVICE);
+
+	drm_gem_object_put(gem_obj);
+
+	return ret;
+}
+
+int thames_ioctl_bo_fini(struct drm_device *ddev, void *data, struct drm_file *file)
+{
+	struct drm_thames_bo_fini *args = data;
+	struct drm_gem_shmem_object *shmem_obj;
+	struct thames_gem_object *thames_obj;
+	struct drm_gem_object *gem_obj;
+
+	if (args->reserved != 0)
+		return -EINVAL;
+
+	gem_obj = drm_gem_object_lookup(file, args->handle);
+	if (!gem_obj)
+		return -ENOENT;
+
+	thames_obj = to_thames_bo(gem_obj);
+	shmem_obj = &thames_obj->base;
+
+	dma_sync_sgtable_for_device(ddev->dev, shmem_obj->sgt, DMA_TO_DEVICE);
+
+	drm_gem_object_put(gem_obj);
+
+	return 0;
+}
diff --git a/drivers/accel/thames/thames_gem.h b/drivers/accel/thames/thames_gem.h
index 785843c40a89a9e84ab634aad77e9ec46111693e..e5a8278e98c578c2903cf23aea1bf887be0389e8 100644
--- a/drivers/accel/thames/thames_gem.h
+++ b/drivers/accel/thames/thames_gem.h
@@ -29,6 +29,10 @@ int thames_ioctl_bo_create(struct drm_device *ddev, void *data, struct drm_file
 
 int thames_ioctl_bo_mmap_offset(struct drm_device *ddev, void *data, struct drm_file *file);
 
+int thames_ioctl_bo_prep(struct drm_device *ddev, void *data, struct drm_file *file);
+
+int thames_ioctl_bo_fini(struct drm_device *ddev, void *data, struct drm_file *file);
+
 int thames_context_create(struct thames_file_priv *priv);
 
 void thames_context_destroy(struct thames_file_priv *priv);

-- 
2.52.0