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Date:   Mon, 7 Mar 2022 17:21:34 -0600
From:   Rob Herring <robh@kernel.org>
To:     Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
        Saravana Kannan <saravanak@google.com>
Cc:     devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org,
        linux-media@vger.kernel.org, Chen-Yu Tsai <wens@csie.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Samuel Holland <samuel@sholland.org>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Frank Rowand <frowand.list@gmail.com>,
        Maxime Ripard <mripard@kernel.org>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Subject: Re: [PATCH RFC v3 1/8] of: Mark interconnects property supplier as
 optional
Message-ID: <YiaTfsMDs7RGob2N@robh.at.kernel.org>
References: <20220302211100.65264-1-paul.kocialkowski@bootlin.com>
 <20220302211100.65264-2-paul.kocialkowski@bootlin.com>
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In-Reply-To: <20220302211100.65264-2-paul.kocialkowski@bootlin.com>
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+Saravana

On Wed, Mar 02, 2022 at 10:10:53PM +0100, Paul Kocialkowski wrote:
> In order to set their correct DMA address offset, some devices rely on
> the device-tree interconnects property which identifies an
> interconnect node that provides a dma-ranges property that can be used
> to set said offset.
> 
> Since that logic is all handled by the generic openfirmware and driver
> code, the device-tree description could be enough to properly set
> the offset.
> 
> However the interconnects property is currently not marked as
> optional, which implies that a driver for the corresponding node
> must be loaded as a requirement. When no such driver exists, this
> results in an endless EPROBE_DEFER which gets propagated to the
> calling driver. This ends up in the driver never loading.
> 
> Marking the interconnects property as optional makes it possible
> to load the driver in that situation, since the EPROBE_DEFER return
> code will no longer be propagated to the driver.
> 
> There might however be undesirable consequences with this change,
> which I do not fully grasp at this point.
> 
> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
> ---
>  drivers/of/property.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/of/property.c b/drivers/of/property.c
> index 8e90071de6ed..ef7c56b510e8 100644
> --- a/drivers/of/property.c
> +++ b/drivers/of/property.c
> @@ -1365,7 +1365,7 @@ static struct device_node *parse_interrupts(struct device_node *np,
>  
>  static const struct supplier_bindings of_supplier_bindings[] = {
>  	{ .parse_prop = parse_clocks, },
> -	{ .parse_prop = parse_interconnects, },
> +	{ .parse_prop = parse_interconnects, .optional = true,},
>  	{ .parse_prop = parse_iommus, .optional = true, },
>  	{ .parse_prop = parse_iommu_maps, .optional = true, },
>  	{ .parse_prop = parse_mboxes, },
> -- 
> 2.35.1
> 
>