[PATCH 3/9] drm/amdgpu: add amdgpu module parameter for zfb

[Christian König]

Hi Feifei,

mhm, so you're approach is to limit the memory the Linux kernel grab 
using the mem= parameter and then give that memory to amdgpu, correct?

If that's the case then this is most likely a NAK. Cause this sounds 
like a perfect example for the CMA.

Never worked with that subsystem before, but in theory you should be 
able to give the cma=1G parameter to the kernel and by doing so you 
reserve 1GB of contiguous memory for use by device drivers.

Going to dig a bit deeper into that and trying to find to documentation 
about it,
Christian.

Am 07.02.2018 um 13:34 schrieb Feifei Xu:
> Users can pass in an array to decide enable/disable Zero Frame Buffer.
> zfb[0] = zfb_size(MB), zfb[1] = zfb_phys_addr(MB).
> If zbf_size > 0, zfb is enabled. Otherwise disabled.
> Usage for example:
>      modprobe amdgpu zfb={256,4096}
>
> Change-Id: I340fcb36b5655f24551056e685b74559d7599680
> Signed-off-by: Feifei Xu <Feifei.Xu at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu.h     | 1 +
>   drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 5 +++++
>   2 files changed, 6 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index 1b4c5ad..be79cb1 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -129,6 +129,7 @@ extern int amdgpu_job_hang_limit;
>   extern int amdgpu_lbpw;
>   extern int amdgpu_compute_multipipe;
>   extern int amdgpu_gpu_recovery;
> +extern ulong amdgpu_zfb[];
>   
>   #ifdef CONFIG_DRM_AMDGPU_SI
>   extern int amdgpu_si_support;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> index 3897179..af84815 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> @@ -132,6 +132,7 @@ int amdgpu_job_hang_limit = 0;
>   int amdgpu_lbpw = -1;
>   int amdgpu_compute_multipipe = -1;
>   int amdgpu_gpu_recovery = -1; /* auto */
> +ulong amdgpu_zfb[2] = {0,4096UL}; /* {0,0x100000000} */
>   
>   MODULE_PARM_DESC(vramlimit, "Restrict VRAM for testing, in megabytes");
>   module_param_named(vramlimit, amdgpu_vram_limit, int, 0600);
> @@ -290,6 +291,10 @@ module_param_named(compute_multipipe, amdgpu_compute_multipipe, int, 0444);
>   MODULE_PARM_DESC(gpu_recovery, "Enable GPU recovery mechanism, (1 = enable, 0 = disable, -1 = auto");
>   module_param_named(gpu_recovery, amdgpu_gpu_recovery, int, 0444);
>   
> +MODULE_PARM_DESC(zfb,
> +		 "Enable Zero Frame Buffer feature (zfb will be set like xxxx,xxxx(zfb_size MB,zfb_phys_addr MB),default disabled)");
> +module_param_array_named(zfb, amdgpu_zfb, ulong, NULL, 0444);
> +
>   #ifdef CONFIG_DRM_AMDGPU_SI
>   
>   int amdgpu_si_support = 1;