linux-kernel - Re: [PATCHv2] net: moxart: use correct accessors for DMA memory

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Message-Id: <20160129.194021.1464359327401868408.davem@davemloft.net>
Date:	Fri, 29 Jan 2016 19:40:21 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	arnd@...db.de
Cc:	linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
	romieu@...zoreil.com, linux-kernel@...r.kernel.org,
	David.Laight@...lab.com
Subject: Re: [PATCHv2] net: moxart: use correct accessors for DMA memory

From: Arnd Bergmann <arnd@...db.de>
Date: Thu, 28 Jan 2016 17:54:33 +0100

> The moxart ethernet driver confuses coherent DMA buffers with
> MMIO registers.
> 
> moxart_ether.c: In function 'moxart_mac_setup_desc_ring':
> moxart_ether.c:146:428: error: passing argument 1 of '__fswab32' makes integer from pointer without a cast [-Werror=int-conversion]
> moxart_ether.c:74:39: warning: incorrect type in argument 3 (different address spaces)
> moxart_ether.c:74:39:    expected void *cpu_addr
> moxart_ether.c:74:39:    got void [noderef] <asn:2>*tx_desc_base
> 
> This leaves the basic logic alone and uses normal pointers for
> the virtual address of the descriptor. As we cannot use readl/writel
> to access them, we also introduce our own moxart_desc_read
> moxart_desc_write helpers that perform the same endianess swap
> as the original code, but without the address space conversion.
> 
> The barriers are made explicit here where needed: Even in the worst-case
> scenario, we just have to use a rmb() after checking ownership so
> we don't read any input data before we are sure it is value, and we
> use wmb() before transferring ownership back to the device.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Applied, thanks.