linux-kernel - Re: [PATCH 01/18] dmaengine: of-dma: Add support for optional router configuration callback

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Message-ID: <20201007054404.GR2968@vkoul-mobl>
Date:   Wed, 7 Oct 2020 11:14:04 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Peter Ujfalusi <peter.ujfalusi@...com>
Cc:     nm@...com, ssantosh@...nel.org, robh+dt@...nel.org,
        vigneshr@...com, dan.j.williams@...el.com, t-kristo@...com,
        lokeshvutla@...com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        dmaengine@...r.kernel.org
Subject: Re: [PATCH 01/18] dmaengine: of-dma: Add support for optional router
 configuration callback

Hi Peter,

On 30-09-20, 12:13, Peter Ujfalusi wrote:
> Additional configuration for the DMA event router might be needed for a
> channel which can not be done during device_alloc_chan_resources callback
> since the router information is not yet present for the drivers.
> 
> If there is a need for additional configuration for the channel if DMA
> router is in use, then the driver can implement the device_router_config
> callback.

So what is the additional information you need, I am looking at the code
below and xlate invokes device_router_config() which driver will
implement..

Are you using this to configure channels based on info from DT?

> 
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
> ---
>  drivers/dma/of-dma.c      | 10 ++++++++++
>  include/linux/dmaengine.h |  2 ++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/drivers/dma/of-dma.c b/drivers/dma/of-dma.c
> index 8a4f608904b9..ec00b20ae8e4 100644
> --- a/drivers/dma/of-dma.c
> +++ b/drivers/dma/of-dma.c
> @@ -75,8 +75,18 @@ static struct dma_chan *of_dma_router_xlate(struct of_phandle_args *dma_spec,
>  		ofdma->dma_router->route_free(ofdma->dma_router->dev,
>  					      route_data);
>  	} else {
> +		int ret = 0;
> +
>  		chan->router = ofdma->dma_router;
>  		chan->route_data = route_data;
> +
> +		if (chan->device->device_router_config)
> +			ret = chan->device->device_router_config(chan);
> +
> +		if (ret) {
> +			dma_release_channel(chan);
> +			chan = ERR_PTR(ret);
> +		}
>  	}
>  
>  	/*
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index dd357a747780..d6197fe875af 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -800,6 +800,7 @@ struct dma_filter {
>   *	by tx_status
>   * @device_alloc_chan_resources: allocate resources and return the
>   *	number of allocated descriptors
> + * @device_router_config: optional callback for DMA router configuration
>   * @device_free_chan_resources: release DMA channel's resources
>   * @device_prep_dma_memcpy: prepares a memcpy operation
>   * @device_prep_dma_xor: prepares a xor operation
> @@ -874,6 +875,7 @@ struct dma_device {
>  	enum dma_residue_granularity residue_granularity;
>  
>  	int (*device_alloc_chan_resources)(struct dma_chan *chan);
> +	int (*device_router_config)(struct dma_chan *chan);
>  	void (*device_free_chan_resources)(struct dma_chan *chan);
>  
>  	struct dma_async_tx_descriptor *(*device_prep_dma_memcpy)(
> -- 
> Peter
> 
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

-- 
~Vinod