linux-kernel - [PATCH v1 01/10] drm/panthor: Factor out GPU_ID register read into separate function

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Message-ID: <20251014094337.1009601-2-karunika.choo@arm.com>
Date: Tue, 14 Oct 2025 10:43:28 +0100
From: Karunika Choo <karunika.choo@....com>
To: dri-devel@...ts.freedesktop.org
Cc: nd@....com,
	Boris Brezillon <boris.brezillon@...labora.com>,
	Steven Price <steven.price@....com>,
	Liviu Dudau <liviu.dudau@....com>,
	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>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v1 01/10] drm/panthor: Factor out GPU_ID register read into separate function

Split the GPU_ID register read into its own helper function. The GPU_ID
value will be used to enable architecture-specific behaviours, which may
also affect how other registers (such as those used for gpu_info) are
read.

This change separates the read operation so that subsequent code can
depend on the intermediate result of processing the GPU_ID.

Signed-off-by: Karunika Choo <karunika.choo@....com>
---
 drivers/gpu/drm/panthor/panthor_hw.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panthor/panthor_hw.c b/drivers/gpu/drm/panthor/panthor_hw.c
index 4f2858114e5e..326a9db0b5c2 100644
--- a/drivers/gpu/drm/panthor/panthor_hw.c
+++ b/drivers/gpu/drm/panthor/panthor_hw.c
@@ -62,7 +62,6 @@ static void panthor_gpu_info_init(struct panthor_device *ptdev)
 {
 	unsigned int i;
 
-	ptdev->gpu_info.gpu_id = gpu_read(ptdev, GPU_ID);
 	ptdev->gpu_info.csf_id = gpu_read(ptdev, GPU_CSF_ID);
 	ptdev->gpu_info.gpu_rev = gpu_read(ptdev, GPU_REVID);
 	ptdev->gpu_info.core_features = gpu_read(ptdev, GPU_CORE_FEATURES);
@@ -117,8 +116,23 @@ static void panthor_hw_info_init(struct panthor_device *ptdev)
 		 ptdev->gpu_info.tiler_present);
 }
 
+static int panthor_hw_gpu_id_init(struct panthor_device *ptdev)
+{
+	ptdev->gpu_info.gpu_id = gpu_read(ptdev, GPU_ID);
+	if (!ptdev->gpu_info.gpu_id)
+		return -ENXIO;
+
+	return 0;
+}
+
 int panthor_hw_init(struct panthor_device *ptdev)
 {
+	int ret = 0;
+
+	ret = panthor_hw_gpu_id_init(ptdev);
+	if (ret)
+		return ret;
+
 	panthor_hw_info_init(ptdev);
 
 	return 0;
-- 
2.49.0