linux-kernel - Re: [PATCH net-next v2 16/18] MIPS: mobileye: add EyeQ5 DMA IOCU support

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Message-ID: <20250627191555.GD1776@horms.kernel.org>
Date: Fri, 27 Jun 2025 20:15:55 +0100
From: Simon Horman <horms@...nel.org>
To: Théo Lebrun <theo.lebrun@...tlin.com>
Cc: Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Nicolas Ferre <nicolas.ferre@...rochip.com>,
	Claudiu Beznea <claudiu.beznea@...on.dev>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>,
	Samuel Holland <samuel.holland@...ive.com>,
	Richard Cochran <richardcochran@...il.com>,
	Russell King <linux@...linux.org.uk>,
	Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
	Vladimir Kondratiev <vladimir.kondratiev@...ileye.com>,
	Gregory CLEMENT <gregory.clement@...tlin.com>,
	Cyrille Pitchen <cyrille.pitchen@...el.com>,
	Harini Katakam <harini.katakam@...inx.com>,
	Rafal Ozieblo <rafalo@...ence.com>,
	Haavard Skinnemoen <hskinnemoen@...el.com>,
	Jeff Garzik <jeff@...zik.org>, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org, linux-mips@...r.kernel.org,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	Tawfik Bayouk <tawfik.bayouk@...ileye.com>
Subject: Re: [PATCH net-next v2 16/18] MIPS: mobileye: add EyeQ5 DMA IOCU
 support

On Fri, Jun 27, 2025 at 11:09:02AM +0200, Théo Lebrun wrote:
> Both Cadence GEM Ethernet controllers on EyeQ5 are hardwired through CM3
> IO Coherency Units (IOCU). For DMA coherent accesses, BIT(36) must be
> set in DMA addresses.
> 
> Implement that in platform-specific dma_map_ops which get attached to
> both instances of `cdns,eyeq5-gem` through a notifier block.
> 
> Signed-off-by: Théo Lebrun <theo.lebrun@...tlin.com>

...

> diff --git a/arch/mips/mobileye/eyeq5-iocu-dma.c b/arch/mips/mobileye/eyeq5-iocu-dma.c

...

> +const struct dma_map_ops eyeq5_iocu_ops = {
> +	.alloc			= eyeq5_iocu_alloc,
> +	.free			= eyeq5_iocu_free,
> +	.alloc_pages_op		= dma_direct_alloc_pages,
> +	.free_pages		= dma_direct_free_pages,
> +	.mmap			= eyeq5_iocu_mmap,
> +	.get_sgtable		= eyeq5_iocu_get_sgtable,
> +	.map_page		= eyeq5_iocu_map_page,
> +	.unmap_page		= eyeq5_iocu_unmap_page,
> +	.map_sg			= eyeq5_iocu_map_sg,
> +	.unmap_sg		= eyeq5_iocu_unmap_sg,
> +	.get_required_mask	= dma_direct_get_required_mask,
> +};
> +EXPORT_SYMBOL(eyeq5_iocu_ops);

Hi Théo,

Does eyeq5_iocu_ops need to be exported?
If so it should probably be declared in a header file somewhere.
But I if not probably the EXPORT_SYMBOL line should be
dropped, and the structure made static.

Flagged by Sparse.

> +
> +static int eyeq5_iocu_notifier(struct notifier_block *nb,
> +			       unsigned long event,
> +			       void *data)
> +{
> +	struct device *dev = data;
> +
> +	/*
> +	 * IOCU routing is hardwired; we must use our above custom
> +	 * routines for cache-coherent DMA on ethernet interfaces.
> +	 */
> +	if (event == BUS_NOTIFY_ADD_DEVICE &&
> +	    device_is_compatible(dev, "mobileye,eyeq5-gem")) {
> +		set_dma_ops(dev, &eyeq5_iocu_ops);
> +		return NOTIFY_OK;
> +	}
> +
> +	return NOTIFY_DONE;
> +}

...