linux-kernel - Re: [PATCH 3/5] net: add Hisilicon Network Subsystem MDIO support

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Message-ID: <20150817091750.GA134983@Turing-Arch-b>
Date:	Mon, 17 Aug 2015 17:17:50 +0800
From:	Kenneth Lee <liguozhu@...ilicon.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	<linux-arm-kernel@...ts.infradead.org>, <robh+dt@...nel.org>,
	<pawel.moll@....com>, <mark.rutland@....com>,
	<ijc+devicetree@...lion.org.uk>, <galak@...eaurora.org>,
	<catalin.marinas@....com>, <will.deacon@....com>,
	<Yisen.Zhuang@...wei.com>, <davem@...emloft.net>,
	<paul.gortmaker@...driver.com>, <dingtianhong@...wei.com>,
	<zhangfei.gao@...aro.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
	<linuxarm@...wei.com>, <salil.mehta@...wei.com>,
	<huangdaode@...ilicon.com>, Kenneth Lee <liguozhu@...wei.com>
Subject: Re: [PATCH 3/5] net: add Hisilicon Network Subsystem MDIO support

Thanks, Arnd, 

You are right. This is the same IP as hip04_mdio.c. We just mis-understand the
hardware design. We will merge them and re-submit the patches.

On Fri, Aug 14, 2015 at 10:57:28PM +0200, Arnd Bergmann wrote:
> On Friday 14 August 2015 18:30:20 Kenneth Lee wrote:
> 
> > +#define MDIO_BASE_ADDR                 0x403C0000
> 
> Does not belong in here (and is not used)
> 
> > +#define MDIO_COMMAND_REG               0x0
> > +#define MDIO_ADDR_REG                  0x4
> > +#define MDIO_WDATA_REG                 0x8
> > +#define MDIO_RDATA_REG                 0xc
> > +#define MDIO_STA_REG                   0x10
> 
> These look suspiciously similar to definitions from
> drivers/net/ethernet/hisilicon/hip04_mdio.c.
> 
> Could the hardware be related? If so, please try to share
> the common parts.
> 
> > +static inline void mdio_write_reg(void *base, u32 reg, u32 value)
> > +{
> > +       u8 __iomem *reg_addr = ACCESS_ONCE(base);
> > +
> > +       writel(value, reg_addr + reg);
> > +}
> > +
> > +#define MDIO_WRITE_REG(a, reg, value) \
> > +       mdio_write_reg((a)->vbase, (reg), (value))
> > 
> 
> Something seems wrong here: why do you have an ACCESS_ONCE() on a
> local variable? Doesn't this just make the code less efficient
> without providing lockless access to shared variables?
> 
> The types are inconsistent here, you should get a warning from
> running this through 'make C=1' because of the missing __iomem
> annotation of the pointer.
> 
> Also, why both a macro and an inline function? Just use an inline
> function.
> 
> 	Arnd
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