linux-kernel - Re: [PATCH 2/2] ASoC: use dma_ops of parent device for acp_audio

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Date:   Wed, 5 Dec 2018 06:45:59 +0000
From:   "Mukunda, Vijendar" <Vijendar.Mukunda@....com>
To:     Yu Zhao <yuzhao@...gle.com>, Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        aroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>
CC:     Daniel Kurtz <djkurtz@...omium.org>,
        "Agrawal, Akshu" <Akshu.Agrawal@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] ASoC: use dma_ops of parent device for acp_audio_dma



On 05/12/18 4:12 AM, Yu Zhao wrote:
> AMD platform device acp_audio_dma can only be created by parent PCI
> device driver (drivers/gpu/drm/amd/amdgpu/amdgpu_acp.c). Pass struct
> device of the parent to snd_pcm_lib_preallocate_pages() so
> dma_alloc_coherent() can use correct dma_ops. Otherwise, it will
> use default dma_ops which is nommu_dma_ops on x86_64 even when
> IOMMU is enabled and set to non passthrough mode.
> 
> Though platform device inherits some dma related fields during its
> creation in mfd_add_device(), we can't simply pass its struct device
> to snd_pcm_lib_preallocate_pages() because dma_ops is not among the
> inherited fields. Even it were, drivers/iommu/amd_iommu.c would
> ignore it because get_device_id() doesn't handle platform device.
> 
> This change shouldn't give us any trouble even struct device of the
> parent becomes null or represents some non PCI device in the future,
> because get_dma_ops() correctly handles null struct device or uses
> the default dma_ops if struct device doesn't have it set.
> 

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

Thanks,
Vijendar
> Signed-off-by: Yu Zhao <yuzhao@...gle.com>
> ---
>   sound/soc/amd/acp-pcm-dma.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/soc/amd/acp-pcm-dma.c b/sound/soc/amd/acp-pcm-dma.c
> index fd3db4c37882..f4011bebc7ec 100644
> --- a/sound/soc/amd/acp-pcm-dma.c
> +++ b/sound/soc/amd/acp-pcm-dma.c
> @@ -1146,18 +1146,21 @@ static int acp_dma_new(struct snd_soc_pcm_runtime *rtd)
>   	struct snd_soc_component *component = snd_soc_rtdcom_lookup(rtd,
>   								    DRV_NAME);
>   	struct audio_drv_data *adata = dev_get_drvdata(component->dev);
> +	struct device *parent = component->dev->parent;
>   
>   	switch (adata->asic_type) {
>   	case CHIP_STONEY:
>   		ret = snd_pcm_lib_preallocate_pages_for_all(rtd->pcm,
>   							    SNDRV_DMA_TYPE_DEV,
> -							    NULL, ST_MIN_BUFFER,
> +							    parent,
> +							    ST_MIN_BUFFER,
>   							    ST_MAX_BUFFER);
>   		break;
>   	default:
>   		ret = snd_pcm_lib_preallocate_pages_for_all(rtd->pcm,
>   							    SNDRV_DMA_TYPE_DEV,
> -							    NULL, MIN_BUFFER,
> +							    parent,
> +							    MIN_BUFFER,
>   							    MAX_BUFFER);
>   		break;
>   	}
>