linux-kernel - Re: [PATCH 1/2] of: device: Allow DMA range map to be set before of_dma_configure

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Message-ID: <YBFkRGMlcyPGKKNT@aptenodytes>
Date:   Wed, 27 Jan 2021 14:01:56 +0100
From:   Paul Kocialkowski <paul.kocialkowski@...tlin.com>
To:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Cc:     Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 1/2] of: device: Allow DMA range map to be set before
 of_dma_configure_id

Hi,

On Fri 15 Jan 21, 18:58, Paul Kocialkowski wrote:
> A mechanism was recently introduced for the sunxi architecture where
> the DMA offset for specific devices (under the MBUS) is set by a common
> driver (sunxi_mbus). This driver calls dma_direct_set_offset to set
> the device's dma_range_map manually.
> 
> However this information was overwritten by of_dma_configure_id, which
> obtains the map from of_dma_get_range (or keeps it NULL when it fails
> and the force_dma argument is true, which is the case for platform
> devices).
> 
> As a result, the dma_range_map was always overwritten and the mechanism
> could not correctly take effect.
> 
> This adds a check to ensure that no previous DMA range map is
> overwritten and prints a warning when the map was already set while
> also being available from dt. In this case, the map that was already
> set is kept.

FYI this patch has been superseded by the following:
https://patchwork.kernel.org/project/linux-mediatek/patch/20210119105203.15530-1-yong.wu@mediatek.com/

Paul

> Fixes: b4bdc4fbf8d0 ("soc: sunxi: Deal with the MBUS DMA offsets in a central place")
> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>
> ---
>  drivers/of/device.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/of/device.c b/drivers/of/device.c
> index aedfaaafd3e7..db1b8634c2c7 100644
> --- a/drivers/of/device.c
> +++ b/drivers/of/device.c
> @@ -181,7 +181,14 @@ int of_dma_configure_id(struct device *dev, struct device_node *np,
>  
>  	arch_setup_dma_ops(dev, dma_start, size, iommu, coherent);
>  
> -	dev->dma_range_map = map;
> +	if (!dev->dma_range_map) {
> +		dev->dma_range_map = map;
> +	} else if (map) {
> +		dev_warn(dev,
> +			 "DMA range map was already set, ignoring range map from dt\n");
> +		kfree(map);
> +	}
> +
>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(of_dma_configure_id);
> -- 
> 2.30.0
> 

-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com

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