Re: [PATCH 7/8] drm/amdgpu: reserve vram for memory training

From: "Tuikov, Luben" <Luben.Tuikov-5C7GfCeVMHo@public.gmane.org>
To: "Yin, Tianci (Rico)" <Tianci.Yin-5C7GfCeVMHo@public.gmane.org>,
	"amd-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org"
	<amd-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org>
Cc: "Deucher,
	Alexander" <Alexander.Deucher-5C7GfCeVMHo@public.gmane.org>,
	"Koenig,
	Christian" <Christian.Koenig-5C7GfCeVMHo@public.gmane.org>
Subject: Re: [PATCH 7/8] drm/amdgpu: reserve vram for memory training
Date: Fri, 11 Oct 2019 23:23:44 +0000	[thread overview]
Message-ID: <9084e67e-adc2-b512-b593-ca218c17a366@amd.com> (raw)
In-Reply-To: <20191011035033.24935-7-tianci.yin-5C7GfCeVMHo@public.gmane.org>

On 2019-10-10 11:50 p.m., Tianci Yin wrote:
> From: "Tianci.Yin" <tianci.yin@amd.com>
> 
> memory training using specific fixed vram segment, reserve these
> segments before anyone may allocate it.
> 
> Change-Id: I1436755813a565608a2857a683f535377620a637
> Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
> Signed-off-by: Tianci.Yin <tianci.yin@amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 96 +++++++++++++++++++++++++
>  1 file changed, 96 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 9da6350a4ba2..42d0fcb98382 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -1667,6 +1667,93 @@ static int amdgpu_ttm_fw_reserve_vram_init(struct amdgpu_device *adev)
>  					  &adev->fw_vram_usage.va);
>  }
>  
> +/*
> + * Memoy training reservation functions
> + */
> +
> +/**
> + * amdgpu_ttm_training_reserve_vram_fini - free memory training reserved vram
> + *
> + * @adev: amdgpu_device pointer
> + *
> + * free memory training reserved vram if it has been reserved.
> + */
> +static int amdgpu_ttm_training_reserve_vram_fini(struct amdgpu_device *adev)
> +{
> +	struct psp_memory_training_context *ctx = &adev->psp.mem_train_ctx;
> +
> +	ctx->init = PSP_MEM_TRAIN_NOT_SUPPORT;
> +	if (ctx->c2p_bo) {
> +		amdgpu_bo_free_kernel(&ctx->c2p_bo, NULL, NULL);
> +		ctx->c2p_bo = NULL;
> +	}

Generally it is a good idea to paragraph your code.
So an empty line between if-statements is a good idea.
However, there is no need in:

ret = f(x);
if (ret) {
	<body of code>
}

if (blah) {
	<body of code>
}

The above are two (2) well-formed paragraphs.

> +	if (ctx->p2c_bo) {
> +		amdgpu_bo_free_kernel(&ctx->p2c_bo, NULL, NULL);
> +		ctx->p2c_bo = NULL;
> +	}
> +
> +	return 0;
> +}
> +
> +/**
> + * amdgpu_ttm_training_reserve_vram_init - create bo vram reservation from memory training
> + *
> + * @adev: amdgpu_device pointer
> + *
> + * create bo vram reservation from memory training.
> + */
> +static int amdgpu_ttm_training_reserve_vram_init(struct amdgpu_device *adev)
> +{
> +	int ret;
> +	struct psp_memory_training_context *ctx = &adev->psp.mem_train_ctx;
> +
> +	memset(ctx, 0, sizeof(*ctx));
> +	if (!adev->fw_vram_usage.mem_train_support) {
> +		DRM_DEBUG("memory training does not support!\n");
> +		return 0;
> +	}
> +
> +	ctx->c2p_train_data_offset = adev->fw_vram_usage.mem_train_fb_loc;
> +	ctx->p2c_train_data_offset = (adev->gmc.mc_vram_size - GDDR6_MEM_TRAINING_OFFSET);
> +	ctx->train_data_size = GDDR6_MEM_TRAINING_DATA_SIZE_IN_BYTES;
> +
> +	DRM_DEBUG("train_data_size:%llx,p2c_train_data_offset:%llx,c2p_train_data_offset:%llx.\n",
> +		  ctx->train_data_size,
> +		  ctx->p2c_train_data_offset,
> +		  ctx->c2p_train_data_offset);
> +
> +	ret = amdgpu_bo_create_kernel_at(adev,
> +					 ctx->p2c_train_data_offset,
> +					 ctx->train_data_size,
> +					 AMDGPU_GEM_DOMAIN_VRAM,
> +					 &ctx->p2c_bo,
> +					 NULL);
> +	if (ret) {
> +		DRM_ERROR("alloc p2c_bo failed(%d)!\n", ret);
> +		ret = -ENOMEM;
> +		goto err_out;
> +	}

NAK!
Why are you re-writing the error code from "amdgpu_bo_create_kenrel_at()"?
Pass the error as is.

> +
> +	ret = amdgpu_bo_create_kernel_at(adev,
> +					 ctx->c2p_train_data_offset,
> +					 ctx->train_data_size,
> +					 AMDGPU_GEM_DOMAIN_VRAM,
> +					 &ctx->c2p_bo,
> +					 NULL);
> +	if (ret) {
> +		DRM_ERROR("alloc c2p_bo failed(%d)!\n", ret);
> +		ret = -ENOMEM;
> +		goto err_out;
> +	}

NAK!
Why are you re-writing the error code from "amdgpu_bo_create_kenrel_at()"?
Pass the error as is.

> +
> +	ctx->init = PSP_MEM_TRAIN_RESERVE_SUCCESS;
> +	return 0;
> +
> +err_out:

Yes... well "err_out" could be any identifier, including
a variable, as our variables follow snake-notation, all lowercase.

Back at the turn of this century, Linux followed capitalized
goto labels to distinguish them from anything else around
in the kernel code:

	goto Bad_err;
	...

	return 0;
Bad_err:
	return bad_gift;
}

To distinguish that a capitalized identifier is a goto label,
"Bad_err" and all lower-case label is just another variable
or function identifier, "bad_gift".

Regards,
Luben

> +	amdgpu_ttm_training_reserve_vram_fini(adev);
> +	return ret;
> +}
> +
>  /**
>   * amdgpu_ttm_init - Init the memory management (ttm) as well as various
>   * gtt/vram related fields.
> @@ -1740,6 +1827,14 @@ int amdgpu_ttm_init(struct amdgpu_device *adev)
>  		return r;
>  	}
>  
> +	/*
> +	 *The reserved vram for memory training must be pinned to the specified
> +	 *place on the VRAM, so reserve it early.
> +	 */
> +	r = amdgpu_ttm_training_reserve_vram_init(adev);
> +	if (r)
> +		return r;
> +
>  	/* allocate memory as required for VGA
>  	 * This is used for VGA emulation and pre-OS scanout buffers to
>  	 * avoid display artifacts while transitioning between pre-OS
> @@ -1825,6 +1920,7 @@ void amdgpu_ttm_fini(struct amdgpu_device *adev)
>  		return;
>  
>  	amdgpu_ttm_debugfs_fini(adev);
> +	amdgpu_ttm_training_reserve_vram_fini(adev);
>  	amdgpu_ttm_fw_reserve_vram_fini(adev);
>  	if (adev->mman.aper_base_kaddr)
>  		iounmap(adev->mman.aper_base_kaddr);
> 

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