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

Wed, 07 Feb 2018 10:49:12 -0800 

Hi Feifei,

ok the correct approach of doing this:
1. Compile the kernel with CONFIG_DMA_CMA.
2. Specify cma=1025M on the kernel command line.
3. Call dma_alloc_coherent() to allocate up to 1GB of memory for ZFB.
Couldn't figure out of hand what alignment is necessary here, but that should just be a typing exercise. 

Regards,
Christian.

Am 07.02.2018 um 14:18 schrieb 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...@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;




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