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

[Christian König]

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.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;
>