[PATCH] drm/amdgpu: Add kernel parameter to force no xgmi

[Luben Tuikov]

On 2020-10-28 10:55, Alex Sierra wrote:
> By enabling this parameter, the system will be forced to use pcie
> interface only for p2p transactions.
> 
> Signed-off-by: Alex Sierra <alex.sierra at amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu.h        | 1 +
>  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 2 +-
>  drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c    | 9 +++++++++
>  3 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index ba65d4f2ab67..3645f00e9f61 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -188,6 +188,7 @@ extern int amdgpu_discovery;
>  extern int amdgpu_mes;
>  extern int amdgpu_noretry;
>  extern int amdgpu_force_asic_type;
> +extern int amdgpu_force_no_xgmi;
>  #ifdef CONFIG_HSA_AMD
>  extern int sched_policy;
>  extern bool debug_evictions;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index 1fe850e0a94d..0a5d97a84017 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -2257,7 +2257,7 @@ static int amdgpu_device_ip_init(struct amdgpu_device *adev)
>  	if (r)
>  		goto init_failed;
>  
> -	if (adev->gmc.xgmi.num_physical_nodes > 1)
> +	if (!amdgpu_force_no_xgmi && adev->gmc.xgmi.num_physical_nodes > 1)
>  		amdgpu_xgmi_add_device(adev);
>  	amdgpu_amdkfd_device_init(adev);
>  
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> index 4b78ecfd35f7..22485067cf31 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> @@ -160,6 +160,7 @@ int amdgpu_force_asic_type = -1;
>  int amdgpu_tmz = 0;
>  int amdgpu_reset_method = -1; /* auto */
>  int amdgpu_num_kcq = -1;
> +int amdgpu_force_no_xgmi = 0;
>  
>  struct amdgpu_mgpu_info mgpu_info = {
>  	.mutex = __MUTEX_INITIALIZER(mgpu_info.mutex),
> @@ -522,6 +523,14 @@ module_param_named(ras_enable, amdgpu_ras_enable, int, 0444);
>  MODULE_PARM_DESC(ras_mask, "Mask of RAS features to enable (default 0xffffffff), only valid when ras_enable == 1");
>  module_param_named(ras_mask, amdgpu_ras_mask, uint, 0444);
>  
> +/**
> + * DOC: force_no_xgmi (uint)
> + * Forces not to use xgmi interface (0 = disable, 1 = enable).

How about using human English here? Perhaps something like,

"Forces not to use" ==> "Disables the use of the XGMI interface ..."

Or, if you use the suggestion Christian posted, you could say something like,

"Enable XGMI for P2P transactions."

Regards,
Luben

> + * Default is 0 (disabled).
> + */
> +MODULE_PARM_DESC(force_no_xgmi, "Force not to use xgmi interface");
> +module_param_named(force_no_xgmi, amdgpu_force_no_xgmi, int, 0600);
> +
>  /**
>   * DOC: si_support (int)
>   * Set SI support driver. This parameter works after set config CONFIG_DRM_AMDGPU_SI. For SI asic, when radeon driver is enabled,
>