netdev - Re: [PATCH v2 05/10] net/fec: add dual fec support for mx28

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Message-ID: <20110105084513.GA26617@pengutronix.de>
Date:	Wed, 5 Jan 2011 09:45:13 +0100
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Shawn Guo <shawn.guo@...escale.com>
Cc:	Baruch Siach <baruch@...s.co.il>, gerg@...pgear.com,
	B32542@...escale.com, netdev@...r.kernel.org,
	u.kleine-koenig@...gutronix.de, w.sang@...gutronix.de,
	r64343@...escale.com, eric@...rea.com, bryan.wu@...onical.com,
	davem@...emloft.net, linux-arm-kernel@...ts.infradead.org,
	lw@...o-electronics.de
Subject: Re: [PATCH v2 05/10] net/fec: add dual fec support for mx28

On Tue, Jan 04, 2011 at 10:13:09PM +0800, Shawn Guo wrote:
> Hi Baruch,
> 
> On Tue, Jan 04, 2011 at 11:59:16AM +0200, Baruch Siach wrote:
> > Hi Shawn,
> > 
> > On Tue, Jan 04, 2011 at 05:24:11PM +0800, Shawn Guo wrote:
> > > This patch is to add mx28 dual fec support. Here are some key notes
> > > for mx28 fec controller.
> > > 
> > >  - mx28 fec design made an assumption that it runs on a
> > >    big-endian system, which is incorrect. As the result, the
> > >    driver has to swap every frame going to and coming from
> > >    the controller.
> > >  - external phys can only be configured by fec0, which means
> > >    fec1 can not work independently and both phys need to be
> > >    configured by mii_bus attached on fec0.
> > >  - mx28 fec reset will get mac address registers reset too.
> > >  - MII/RMII mode and 10M/100M speed are configured differently
> > >    from i.mx/mxs fec controller.
> > >  - ETHER_EN bit must be set to get interrupt work.
> > > 
> > > Signed-off-by: Shawn Guo <shawn.guo@...escale.com>
> > > ---
> > > Changes for v2:
> > >  - Use module parameter fec.macaddr over new kernel command line
> > >    fec_mac to pass mac address
> > 
> > Since you introduce this new kernel command line parameter in patch #3 of this 
> > series, why not just make it right in the first place? This should make both 
> > patches smaller and easier for review.
> > 
> > >  - Update comment in fec_get_mac() to stop using confusing word
> > >    "default"
> > >  - Fix copyright breakage in fec.h
> > 
> > Ditto.
> > 
> Sorry for rushing to send the patch set out. All these updates
> should happen on patch #3 than #5.  This is a serious problem,
> and I will fix it soon and resend as v3.
> 
> > >  drivers/net/Kconfig |    7 ++-
> > >  drivers/net/fec.c   |  139 ++++++++++++++++++++++++++++++++++++++++----------
> > >  drivers/net/fec.h   |    5 +-
> > >  include/linux/fec.h |    3 +-
> > >  4 files changed, 120 insertions(+), 34 deletions(-)
> > 
> > [snip]
> > 
> > > diff --git a/drivers/net/fec.c b/drivers/net/fec.c
> > > index f147508..b2b3e37 100644
> > > --- a/drivers/net/fec.c
> > > +++ b/drivers/net/fec.c
> > > @@ -17,6 +17,8 @@
> > >   *
> > >   * Bug fixes and cleanup by Philippe De Muyter (phdm@...qel.be)
> > >   * Copyright (c) 2004-2006 Macq Electronique SA.
> > > + *
> > > + * Copyright (C) 2010 Freescale Semiconductor, Inc.
> > >   */
> > >  
> > >  #include <linux/module.h>
> > > @@ -45,21 +47,34 @@
> > >  
> > >  #include <asm/cacheflush.h>
> > >  
> > > -#ifndef CONFIG_ARCH_MXC
> > > +#if !defined(CONFIG_ARCH_MXC) && !defined(CONFIG_SOC_IMX28)
> > >  #include <asm/coldfire.h>
> > >  #include <asm/mcfsim.h>
> > >  #endif
> > >  
> > >  #include "fec.h"
> > >  
> > > -#ifdef CONFIG_ARCH_MXC
> > > -#include <mach/hardware.h>
> > 
> > Since you now remove mach/hardware.h for ARCH_MXC, does this build for all 
> > i.MX variants?
> > 
> Did the test build for mx25, mx27, mx3 and mx51.
> 
> > > +#ifdef CONFIG_SOC_IMX28
> > > +/*
> > > + * mx28 does not have MIIGSK registers
> > > + */
> > > +#undef FEC_MIIGSK_ENR
> > > +#include <mach/mxs.h>
> > > +#else
> > > +#define cpu_is_mx28()	(0)
> > > +#endif
> > 
> > This breaks kernels for multiple archs (e.g. i.MX28 and i.MX25). Please use 
> > run-time detection of CPU type, and do the MII/RMII etc. configuration 
> > accordingly.
> > 
> I do not find a good way to detect cpu type.  Neither adding a new
> platform data field nor using __machine_arch_type to enumerate all
> mx28 based machine (though there is only one currently) seems to be
> good for me.
> 
> I will try to manipulate some mx28 unique register to identify mx28
> from other i.mx variants.  Hopefully, it will work.

There won't be a register which you can safely read on all i.MX
variants.
Why don't you implement it the same way the other i.MX do? They do not
need SoC detection and the macro expands to 0 at compile time when the
cpu is not enabled.

Sascha


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