linux-kernel - Re: [PATCH 1/2] smc91x: always use 8-bit access if necessary

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Date:   Thu, 25 Aug 2016 23:33:08 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Nicolas Pitre <nico@...xnic.net>,
        "David S. Miller" <davem@...emloft.net>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] smc91x: always use 8-bit access if necessary

On Thu, Aug 25, 2016 at 04:46:20PM +0200, Arnd Bergmann wrote:
> +#define SMC_out16(x, ioaddr, reg)					     \
> +do {									     \
> +	if (SMC_CAN_USE_8BIT && !SMC_16BIT(lp)) {			     \
> +		unsigned int __val16 = (x);				     \
> +		SMC_outb(__val16, ioaddr, reg );			     \
> +		SMC_outb(__val16 >> 8, ioaddr, reg + (1 << SMC_IO_SHIFT));   \
> +	} else {							     \
> +		SMC_outw(x, ioaddr, reg);				     \
> +	}								     \

This is insufficient.  If you look at how SMC_REG works, you'll notice
that it has side effects which can disrupt other accesses (it reads
the bank register if debugging is enabled.)

In any case, please wait for my tested patch for this.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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