[PATCH] drm/amdkfd: Improve function get_sdma_rlc_reg_offset()

[Felix Kuehling]

On 2019-12-13 8:38, Yong Zhao wrote:
> This prevents the NULL pointer access when there are fewer than 8 sdma
> engines.

I don't see where you got a NULL pointer in the old code. Also this 
change is in an Arcturus-specific source file. AFAIK Arcturus always has 
8 SDMA engines.

The new code is much longer than the old code. I don't see how that's an 
improvement. See one more comment inline.


>
> Change-Id: Iabae9bff7546b344720905d5d4a5cfc066a79d25
> Signed-off-by: Yong Zhao <Yong.Zhao at amd.com>
> ---
>   .../drm/amd/amdgpu/amdgpu_amdkfd_arcturus.c   | 64 ++++++++++++-------
>   1 file changed, 42 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_arcturus.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_arcturus.c
> index 3c119407dc34..2ad088f10493 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_arcturus.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_arcturus.c
> @@ -71,32 +71,52 @@ static uint32_t get_sdma_rlc_reg_offset(struct amdgpu_device *adev,
>   				unsigned int engine_id,
>   				unsigned int queue_id)
>   {
> -	uint32_t sdma_engine_reg_base[8] = {
> -		SOC15_REG_OFFSET(SDMA0, 0,
> -				 mmSDMA0_RLC0_RB_CNTL) - mmSDMA0_RLC0_RB_CNTL,
> -		SOC15_REG_OFFSET(SDMA1, 0,
> -				 mmSDMA1_RLC0_RB_CNTL) - mmSDMA1_RLC0_RB_CNTL,
> -		SOC15_REG_OFFSET(SDMA2, 0,
> -				 mmSDMA2_RLC0_RB_CNTL) - mmSDMA2_RLC0_RB_CNTL,
> -		SOC15_REG_OFFSET(SDMA3, 0,
> -				 mmSDMA3_RLC0_RB_CNTL) - mmSDMA3_RLC0_RB_CNTL,
> -		SOC15_REG_OFFSET(SDMA4, 0,
> -				 mmSDMA4_RLC0_RB_CNTL) - mmSDMA4_RLC0_RB_CNTL,
> -		SOC15_REG_OFFSET(SDMA5, 0,
> -				 mmSDMA5_RLC0_RB_CNTL) - mmSDMA5_RLC0_RB_CNTL,
> -		SOC15_REG_OFFSET(SDMA6, 0,
> -				 mmSDMA6_RLC0_RB_CNTL) - mmSDMA6_RLC0_RB_CNTL,
> -		SOC15_REG_OFFSET(SDMA7, 0,
> -				 mmSDMA7_RLC0_RB_CNTL) - mmSDMA7_RLC0_RB_CNTL
> -	};
> -
> -	uint32_t retval = sdma_engine_reg_base[engine_id]

I'm not sure where you were getting a NULL pointer, but I guess this 
could have used a range check to make sure engine_id is < 8 before 
indexing into the array. The equivalent in the switch statement would be 
a default case. See below.


> +	uint32_t sdma_engine_reg_base;
> +	uint32_t sdma_rlc_reg_offset;
> +
> +	switch (engine_id) {
> +	case 0:
> +		sdma_engine_reg_base = SOC15_REG_OFFSET(SDMA0, 0,
> +				mmSDMA0_RLC0_RB_CNTL) - mmSDMA0_RLC0_RB_CNTL;
> +		break;
> +	case 1:
> +		sdma_engine_reg_base = SOC15_REG_OFFSET(SDMA1, 0,
> +				mmSDMA1_RLC0_RB_CNTL) - mmSDMA1_RLC0_RB_CNTL;
> +		break;
> +	case 2:
> +		sdma_engine_reg_base = SOC15_REG_OFFSET(SDMA2, 0,
> +				mmSDMA2_RLC0_RB_CNTL) - mmSDMA2_RLC0_RB_CNTL;
> +		break;
> +	case 3:
> +		sdma_engine_reg_base = SOC15_REG_OFFSET(SDMA3, 0,
> +				mmSDMA3_RLC0_RB_CNTL) - mmSDMA3_RLC0_RB_CNTL;
> +		break;
> +	case 4:
> +		sdma_engine_reg_base = SOC15_REG_OFFSET(SDMA4, 0,
> +				mmSDMA4_RLC0_RB_CNTL) - mmSDMA4_RLC0_RB_CNTL;
> +		break;
> +	case 5:
> +		sdma_engine_reg_base = SOC15_REG_OFFSET(SDMA5, 0,
> +				mmSDMA5_RLC0_RB_CNTL) - mmSDMA5_RLC0_RB_CNTL;
> +		break;
> +	case 6:
> +		sdma_engine_reg_base = SOC15_REG_OFFSET(SDMA6, 0,
> +				mmSDMA6_RLC0_RB_CNTL) - mmSDMA6_RLC0_RB_CNTL;
> +		break;
> +	case 7:
> +		sdma_engine_reg_base = SOC15_REG_OFFSET(SDMA7, 0,
> +				mmSDMA7_RLC0_RB_CNTL) - mmSDMA7_RLC0_RB_CNTL;
> +		break;
> +

Do you need a default case for the switch statement? I think you get a 
compiler warning without one.

Regards,
   Felix


> +	}
> +
> +	sdma_rlc_reg_offset = sdma_engine_reg_base
>   		+ queue_id * (mmSDMA0_RLC1_RB_CNTL - mmSDMA0_RLC0_RB_CNTL);
>   
>   	pr_debug("RLC register offset for SDMA%d RLC%d: 0x%x\n", engine_id,
> -			queue_id, retval);
> +			queue_id, sdma_rlc_reg_offset);
>   
> -	return retval;
> +	return sdma_rlc_reg_offset;
>   }
>   
>   static int kgd_hqd_sdma_load(struct kgd_dev *kgd, void *mqd,