linux-kernel - [PATCH 3/4] drm/msm/adreno: Add a modparam to skip GPU

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Message-Id: <20250902-assorted-sept-1-v1-3-f3ec9baed513@oss.qualcomm.com>
Date: Tue, 02 Sep 2025 17:20:02 +0530
From: Akhil P Oommen <akhilpo@....qualcomm.com>
To: Rob Clark <robin.clark@....qualcomm.com>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Jordan Crouse <jordan@...micpenguin.net>,
        Jonathan Marek <jonathan@...ek.ca>
Cc: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Akhil P Oommen <akhilpo@....qualcomm.com>
Subject: [PATCH 3/4] drm/msm/adreno: Add a modparam to skip GPU

During bringup of a new GPU support, it is convenient to have knob to
quickly disable GPU, but keep the display support. This helps to
fallback to 'kms_swrast' in case of bootup issues due to GPU. Add a
modparam to support this.

Signed-off-by: Akhil P Oommen <akhilpo@....qualcomm.com>
---
 drivers/gpu/drm/msm/adreno/adreno_device.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/msm/adreno/adreno_device.c b/drivers/gpu/drm/msm/adreno/adreno_device.c
index 50945bfe9b4992118f23db3cd17ac348be9f9c9d..28f744f3caf7c59412aab06f912cd09a01e185ea 100644
--- a/drivers/gpu/drm/msm/adreno/adreno_device.c
+++ b/drivers/gpu/drm/msm/adreno/adreno_device.c
@@ -24,6 +24,10 @@ bool disable_acd;
 MODULE_PARM_DESC(disable_acd, "Forcefully disable GPU ACD");
 module_param_unsafe(disable_acd, bool, 0400);
 
+static bool skip_gpu;
+MODULE_PARM_DESC(no_gpu, "Disable GPU driver register (0=enable GPU driver register (default), 1=skip GPU driver register");
+module_param(skip_gpu, bool, 0400);
+
 extern const struct adreno_gpulist a2xx_gpulist;
 extern const struct adreno_gpulist a3xx_gpulist;
 extern const struct adreno_gpulist a4xx_gpulist;
@@ -184,6 +188,9 @@ bool adreno_has_gpu(struct device_node *node)
 	uint32_t chip_id;
 	int ret;
 
+	if (skip_gpu)
+		return false;
+
 	ret = find_chipid(node, &chip_id);
 	if (ret)
 		return false;
@@ -404,10 +411,16 @@ static struct platform_driver adreno_driver = {
 
 void __init adreno_register(void)
 {
+	if (skip_gpu)
+		return;
+
 	platform_driver_register(&adreno_driver);
 }
 
 void __exit adreno_unregister(void)
 {
+	if (skip_gpu)
+		return;
+
 	platform_driver_unregister(&adreno_driver);
 }

-- 
2.50.1