linux-kernel - Re: [PATCH v3 4/5] media: iris: select appropriate DMA device for internal buffers

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Message-ID: <000a9208-4a4d-458c-bf28-de4b10ed0678@linaro.org>
Date: Fri, 27 Jun 2025 18:07:35 +0100
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To: Vikash Garodia <quic_vgarodia@...cinc.com>,
 Dikshita Agarwal <quic_dikshita@...cinc.com>,
 Abhinav Kumar <abhinav.kumar@...ux.dev>,
 Mauro Carvalho Chehab <mchehab@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Cc: linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/5] media: iris: select appropriate DMA device for
 internal buffers

On 27/06/2025 16:48, Vikash Garodia wrote:
> When a non-pixel device (np_dev) exists, it is preferred for DMA
> operations for internal buffers which are specific to bitstream data
> processing. DPB(decoded picture buffer) buffers are internal buffers
> associated with pixel buffers, hence they are not part of "non_pixel"
> device.
> 
> Signed-off-by: Vikash Garodia <quic_vgarodia@...cinc.com>
> ---
>   drivers/media/platform/qcom/iris/iris_buffer.c | 15 +++++++++++++--
>   1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/platform/qcom/iris/iris_buffer.c b/drivers/media/platform/qcom/iris/iris_buffer.c
> index e5c5a564fcb81e77746df8c4797a10a07f2ae946..0bf6041936175d03a51985be148e78894fc3e990 100644
> --- a/drivers/media/platform/qcom/iris/iris_buffer.c
> +++ b/drivers/media/platform/qcom/iris/iris_buffer.c
> @@ -265,6 +265,7 @@ static int iris_create_internal_buffer(struct iris_inst *inst,
>   	struct iris_buffers *buffers = &inst->buffers[buffer_type];
>   	struct iris_core *core = inst->core;
>   	struct iris_buffer *buffer;
> +	struct device *dev;
>   
>   	if (!buffers->size)
>   		return 0;
> @@ -280,7 +281,11 @@ static int iris_create_internal_buffer(struct iris_inst *inst,
>   	buffer->dma_attrs = DMA_ATTR_WRITE_COMBINE | DMA_ATTR_NO_KERNEL_MAPPING;
>   	list_add_tail(&buffer->list, &buffers->list);
>   
> -	buffer->kvaddr = dma_alloc_attrs(core->dev, buffer->buffer_size,
> +	dev = core->np_dev ? core->np_dev : core->dev;
> +	if (buffer->type == BUF_DPB)
> +		dev = core->dev;
> +
> +	buffer->kvaddr = dma_alloc_attrs(dev, buffer->buffer_size,
>   					 &buffer->device_addr, GFP_KERNEL, buffer->dma_attrs);
>   	if (!buffer->kvaddr)
>   		return -ENOMEM;
> @@ -367,9 +372,15 @@ int iris_queue_internal_buffers(struct iris_inst *inst, u32 plane)
>   int iris_destroy_internal_buffer(struct iris_inst *inst, struct iris_buffer *buffer)
>   {
>   	struct iris_core *core = inst->core;
> +	struct device *dev;
> +
> +	dev = core->np_dev ? core->np_dev : core->dev;
> +
> +	if (buffer->type == BUF_DPB)
> +		dev = core->dev;

Again I think the hooking of dev is clearer with if/else instead of 
ternary operators.

Its not against the coding standard to my knowledge ..

>   
>   	list_del(&buffer->list);
> -	dma_free_attrs(core->dev, buffer->buffer_size, buffer->kvaddr,
> +	dma_free_attrs(dev, buffer->buffer_size, buffer->kvaddr,
>   		       buffer->device_addr, buffer->dma_attrs);
>   	kfree(buffer);
>   
> 
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>