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@oss.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

On 9/2/25 1:50 PM, Akhil P Oommen wrote:
> 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.

I'm not entirely opposed, but slapping a // in front of the compatible
in the dt works just as well

Konrad

On Tue, Sep 02, 2025 at 02:30:48PM +0200, Konrad Dybcio wrote:
> On 9/2/25 1:50 PM, Akhil P Oommen wrote:
> > 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.
> 
> I'm not entirely opposed, but slapping a // in front of the compatible
> in the dt works just as well

Which requires rebuilding and reprovisioning

> 
> Konrad

-- 
With best wishes
Dmitry

On 9/2/25 3:02 PM, Dmitry Baryshkov wrote:
> On Tue, Sep 02, 2025 at 02:30:48PM +0200, Konrad Dybcio wrote:
>> On 9/2/25 1:50 PM, Akhil P Oommen wrote:
>>> 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.
>>
>> I'm not entirely opposed, but slapping a // in front of the compatible
>> in the dt works just as well
> 
> Which requires rebuilding and reprovisioning

Fair

Konrad

On Wed, Sep 03, 2025 at 11:25:49AM +0200, Konrad Dybcio wrote:
> On 9/2/25 3:02 PM, Dmitry Baryshkov wrote:
> > On Tue, Sep 02, 2025 at 02:30:48PM +0200, Konrad Dybcio wrote:
> >> On 9/2/25 1:50 PM, Akhil P Oommen wrote:
> >>> 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.
> >>
> >> I'm not entirely opposed, but slapping a // in front of the compatible
> >> in the dt works just as well
> > 
> > Which requires rebuilding and reprovisioning
> 
> Fair

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>



-- 
With best wishes
Dmitry