Re: [PATCH 1/2] ASoC: use DMA addr rather than CPU pa for acp_audio_dma

["Mukunda, Vijendar" <Vijendar.Mukunda@amd.com>]

On 05/12/18 4:12 AM, Yu Zhao wrote:
> We shouldn't assume CPU physical address we get from page_to_phys()
> is same as DMA address we get from dma_alloc_coherent(). On x86_64,
> we won't run into any problem with the assumption when dma_ops is
> nommu_dma_ops. However, DMA address is IOVA when IOMMU is enabled.
> And it's most likely different from CPU physical address when AMD
> IOMMU is not in passthrough mode.

This is really a good fix. We will apply this patch changes for Raven 
platform also.

Thanks,
Vijendar
> 
> Signed-off-by: Yu Zhao <yuzhao@google.com>
> ---
>   sound/soc/amd/acp-pcm-dma.c | 15 +++++----------
>   sound/soc/amd/acp.h         |  2 +-
>   2 files changed, 6 insertions(+), 11 deletions(-)
> 
> diff --git a/sound/soc/amd/acp-pcm-dma.c b/sound/soc/amd/acp-pcm-dma.c
> index cdebab2f8ce5..fd3db4c37882 100644
> --- a/sound/soc/amd/acp-pcm-dma.c
> +++ b/sound/soc/amd/acp-pcm-dma.c
> @@ -303,11 +303,10 @@ static void set_acp_to_i2s_dma_descriptors(void __iomem *acp_mmio, u32 size,
>   }
>   
>   /* Create page table entries in ACP SRAM for the allocated memory */
> -static void acp_pte_config(void __iomem *acp_mmio, struct page *pg,
> +static void acp_pte_config(void __iomem *acp_mmio, dma_addr_t addr,
>   			   u16 num_of_pages, u32 pte_offset)
>   {
>   	u16 page_idx;
> -	u64 addr;
>   	u32 low;
>   	u32 high;
>   	u32 offset;
> @@ -317,7 +316,6 @@ static void acp_pte_config(void __iomem *acp_mmio, struct page *pg,
>   		/* Load the low address of page int ACP SRAM through SRBM */
>   		acp_reg_write((offset + (page_idx * 8)),
>   			      acp_mmio, mmACP_SRBM_Targ_Idx_Addr);
> -		addr = page_to_phys(pg);
>   
>   		low = lower_32_bits(addr);
>   		high = upper_32_bits(addr);
> @@ -333,7 +331,7 @@ static void acp_pte_config(void __iomem *acp_mmio, struct page *pg,
>   		acp_reg_write(high, acp_mmio, mmACP_SRBM_Targ_Idx_Data);
>   
>   		/* Move to next physically contiguos page */
> -		pg++;
> +		addr += PAGE_SIZE;
>   	}
>   }
>   
> @@ -343,7 +341,7 @@ static void config_acp_dma(void __iomem *acp_mmio,
>   {
>   	u16 ch_acp_sysmem, ch_acp_i2s;
>   
> -	acp_pte_config(acp_mmio, rtd->pg, rtd->num_of_pages,
> +	acp_pte_config(acp_mmio, rtd->dma_addr, rtd->num_of_pages,
>   		       rtd->pte_offset);
>   
>   	if (rtd->direction == SNDRV_PCM_STREAM_PLAYBACK) {
> @@ -850,7 +848,6 @@ static int acp_dma_hw_params(struct snd_pcm_substream *substream,
>   	int status;
>   	uint64_t size;
>   	u32 val = 0;
> -	struct page *pg;
>   	struct snd_pcm_runtime *runtime;
>   	struct audio_substream_data *rtd;
>   	struct snd_soc_pcm_runtime *prtd = substream->private_data;
> @@ -986,16 +983,14 @@ static int acp_dma_hw_params(struct snd_pcm_substream *substream,
>   		return status;
>   
>   	memset(substream->runtime->dma_area, 0, params_buffer_bytes(params));
> -	pg = virt_to_page(substream->dma_buffer.area);
>   
> -	if (pg) {
> +	if (substream->dma_buffer.area) {
>   		acp_set_sram_bank_state(rtd->acp_mmio, 0, true);
>   		/* Save for runtime private data */
> -		rtd->pg = pg;
> +		rtd->dma_addr = substream->dma_buffer.addr;
>   		rtd->order = get_order(size);
>   
>   		/* Fill the page table entries in ACP SRAM */
> -		rtd->pg = pg;
>   		rtd->size = size;
>   		rtd->num_of_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
>   		rtd->direction = substream->stream;
> diff --git a/sound/soc/amd/acp.h b/sound/soc/amd/acp.h
> index dbbb1a85638d..e5ab6c6040a6 100644
> --- a/sound/soc/amd/acp.h
> +++ b/sound/soc/amd/acp.h
> @@ -123,7 +123,7 @@ enum acp_dma_priority_level {
>   };
>   
>   struct audio_substream_data {
> -	struct page *pg;
> +	dma_addr_t dma_addr;
>   	unsigned int order;
>   	u16 num_of_pages;
>   	u16 i2s_instance;
>