linux-kernel - [PATCH RFC 5/6] drm/amdgpu: don't wake up the GPU for mmGB_ADDR

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Message-Id: <20250731-b4-dont-wake-next-v1-5-e51bdc347fa3@gmail.com>
Date: Thu, 31 Jul 2025 07:36:38 +0200
From: Philipp Zabel <philipp.zabel@...il.com>
To: Alex Deucher <alexander.deucher@....com>, 
 Christian König <christian.koenig@....com>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org, 
 linux-kernel@...r.kernel.org, Philipp Zabel <p.zabel@...gutronix.de>, 
 Philipp Zabel <philipp.zabel@...il.com>
Subject: [PATCH RFC 5/6] drm/amdgpu: don't wake up the GPU for
 mmGB_ADDR_CONFIG register read

Don't wake the GPU if libdrm queries the mmGB_ADDR_CONFIG register
value during amdgpu_query_gpu_info_init(). Instead, return the already
cached value adev->gfx.config.gb_addr_config.

Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2295
Signed-off-by: Philipp Zabel <philipp.zabel@...il.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
index fe1347a4075c4..ed4d7d72f2065 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
@@ -883,6 +883,16 @@ int amdgpu_info_ioctl(struct drm_device *dev, void *data, struct drm_file *filp)
 
 		alloc_size = info->read_mmr_reg.count * sizeof(*regs);
 
+		if (info->read_mmr_reg.dword_offset == 0x263e &&
+		    info->read_mmr_reg.count == 1) {
+			/* Return cached value of mmGB_ADDR_CONFIG */
+			regs[0] = adev->gfx.config.gb_addr_config;
+
+			n = copy_to_user(out, regs, min(size, alloc_size));
+			kfree(regs);
+			return n ? -EFAULT : 0;
+		}
+
 		ret = pm_runtime_get_sync(dev->dev);
 		if (ret < 0) {
 			pm_runtime_put_autosuspend(dev->dev);

-- 
2.50.1