[PATCH 2/8] drm/amdgpu: add a generic fb accessing helper function

Fri Oct 11 22:44:28 UTC 2019

On 2019-10-10 11:50 p.m., Tianci Yin wrote:
> From: "Tianci.Yin" <tianci.yin at amd.com>
> 
> add a generic helper function for accessing framebuffer via MMIO
> 
> Change-Id: I4baa0aa53c93a94c2eff98c6211a61f369239982
> Reviewed-by: Alex Deucher <alexander.deucher at amd.com>
> Signed-off-by: Tianci.Yin <tianci.yin at amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu.h           |  2 ++
>  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c    | 34 +++++++++++++++++++
>  drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c | 13 +------
>  3 files changed, 37 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index 51ccf175cda0..1102e6bae5d5 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -991,6 +991,8 @@ int amdgpu_device_init(struct amdgpu_device *adev,
>  void amdgpu_device_fini(struct amdgpu_device *adev);
>  int amdgpu_gpu_wait_for_idle(struct amdgpu_device *adev);
>  
> +int amdgpu_device_vram_access(struct amdgpu_device *adev, loff_t pos,
> +			      uint32_t *buf, size_t size, bool write);
>  uint32_t amdgpu_mm_rreg(struct amdgpu_device *adev, uint32_t reg,
>  			uint32_t acc_flags);
>  void amdgpu_mm_wreg(struct amdgpu_device *adev, uint32_t reg, uint32_t v,
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index 598158e95ec1..fb21ec1f8a61 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -154,6 +154,40 @@ bool amdgpu_device_is_px(struct drm_device *dev)
>  	return false;
>  }
>  
> +/**
> + * VRAM access helper functions.
> + *
> + * amdgpu_device_vram_access - read/write a buffer in vram
> + *
> + * @adev: amdgpu_device pointer
> + * @pos: offset of the buffer in vram
> + * @buf: virtual address of the buffer in system memory
> + * @size: read/write size, sizeof(@buf) must > @size
> + * @write: true - write to vram, otherwise - read from vram
> + *
> + * Returns 0 on success or an -error on failure.

Really? Where?
This function seems to return 0.
Traditionally read/write functions
return the number of bytes read/written or error.
You do neither. Just define it void.

> + */
> +int amdgpu_device_vram_access(struct amdgpu_device *adev, loff_t pos,
> +			      uint32_t *buf, size_t size, bool write)
> +{
> +	uint64_t end = pos + size;

NAK! to preinitializing automatic variables.

> +	unsigned long flags;
> +
> +	while (pos < end) {
> +		spin_lock_irqsave(&adev->mmio_idx_lock, flags);
> +		WREG32_NO_KIQ(mmMM_INDEX, ((uint32_t)pos) | 0x80000000);
> +		WREG32_NO_KIQ(mmMM_INDEX_HI, pos >> 31);
> +		if (write)
> +			WREG32_NO_KIQ(mmMM_DATA, *buf++);
> +		else
> +			*buf++ = RREG32_NO_KIQ(mmMM_DATA);
> +		spin_unlock_irqrestore(&adev->mmio_idx_lock, flags);
> +		pos += 4;
> +	}

NAK! to this this:

while (pos < end) {     <---+
	<body of loop>      |--> Part of the loop definition
	pos += 4;       <---+
}

Instead of breaking up the loop definition like this,
use a for-loop, and DO NOT preinitialize the "end" variable,
and also protect from overflow, all like this:

last = size - 1;
for (last += pos; pos <= last; pos += 4) {
	<body of loop>
}

I mentioned the why of this in my previous review of the same
topic patchset over the same while loop fiasco.

Regards,
Luben

> +
> +	return 0;
> +}
> +
>  /*
>   * MMIO register access helper functions.
>   */
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
> index db2dab3a6dff..324c2d605f54 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
> @@ -134,21 +134,10 @@ static int hw_id_map[MAX_HWIP] = {
>  
>  static int amdgpu_discovery_read_binary(struct amdgpu_device *adev, uint8_t *binary)
>  {
> -	uint32_t *p = (uint32_t *)binary;
>  	uint64_t vram_size = (uint64_t)RREG32(mmRCC_CONFIG_MEMSIZE) << 20;
>  	uint64_t pos = vram_size - BINARY_MAX_SIZE;
> -	unsigned long flags;
> -
> -	while (pos < vram_size) {
> -		spin_lock_irqsave(&adev->mmio_idx_lock, flags);
> -		WREG32_NO_KIQ(mmMM_INDEX, ((uint32_t)pos) | 0x80000000);
> -		WREG32_NO_KIQ(mmMM_INDEX_HI, pos >> 31);
> -		*p++ = RREG32_NO_KIQ(mmMM_DATA);
> -		spin_unlock_irqrestore(&adev->mmio_idx_lock, flags);
> -		pos += 4;
> -	}
>  
> -	return 0;
> +	return amdgpu_device_vram_access(adev, pos, (uint32_t *)binary, BINARY_MAX_SIZE, false);
>  }
>  
>  static uint16_t amdgpu_discovery_calculate_checksum(uint8_t *data, uint32_t size)
> 