linux-kernel - Re: [PATCH v2 1/2] ARM: kirkwood: retain MAC address for DT ethernet

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Date:	Thu, 3 Oct 2013 15:04:37 -0400
From:	Jason Cooper <jason@...edaemon.net>
To:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
Cc:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	Andrew Lunn <andrew@...n.ch>,
	Russell King <linux@....linux.org.uk>,
	Grant Likely <grant.likely@...aro.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Mike Turquette <mturquette@...aro.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] ARM: kirkwood: retain MAC address for DT
 ethernet

On Thu, Oct 03, 2013 at 04:02:02PM -0300, Ezequiel Garcia wrote:
> On Thu, Oct 03, 2013 at 08:56:08PM +0200, Sebastian Hesselbarth wrote:
> > Ethernet IP on Kirkwood SoCs loose their MAC address register content
> > if clock gated. To allow modular ethernet driver setups and gated clocks
> > also on non-DT capable bootloaders, we fixup port device nodes with no
> > valid MAC address property. This patch copies MAC address register
> > contents set up by bootloaders early, notably before ethernet clocks
> > are gated. While at it, also reorder call sequence in _dt_init.
> > 
> > Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
> > ---
> > Changelog:
> > v1->v2:
> > - check for gated clock before accessing eth registers
> >   (Suggested by Andrew Lunn)
> > 
> > TBH, as there is no "official" clk_is_enabled but just the __clk_is_enabled
> > one, this is close to abuse of CCF API. Actually, there should either be an
> > clk_is_enabled or we enable the clock, copy a possible invalid MAC address
> > and disable the clock again. (Added Mike, who might have an opinion about
> > clk_is_enabled)
> > 
> > Cc: Jason Cooper <jason@...edaemon.net>
> > Cc: Andrew Lunn <andrew@...n.ch>
> > Cc: Russell King <linux@....linux.org.uk>
> > Cc: Grant Likely <grant.likely@...aro.org>
> > Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> > Cc: Jason Gunthorpe <jgunthorpe@...idianresearch.com>
> > Cc: Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
> > Cc: Mike Turquette <mturquette@...aro.org>
> > Cc: linux-arm-kernel@...ts.infradead.org
> > Cc: linux-kernel@...r.kernel.org
> > ---
> >  arch/arm/mach-kirkwood/board-dt.c |   77 +++++++++++++++++++++++++++++++++++--
> >  1 file changed, 74 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/arm/mach-kirkwood/board-dt.c b/arch/arm/mach-kirkwood/board-dt.c
> > index 82d3ad8..f5f35bb 100644
> > --- a/arch/arm/mach-kirkwood/board-dt.c
> > +++ b/arch/arm/mach-kirkwood/board-dt.c
> > @@ -13,6 +13,8 @@
> >  #include <linux/kernel.h>
> >  #include <linux/init.h>
> >  #include <linux/of.h>
> > +#include <linux/of_address.h>
> > +#include <linux/of_net.h>
> >  #include <linux/of_platform.h>
> >  #include <linux/clk-provider.h>
> >  #include <linux/clocksource.h>
> > @@ -66,6 +68,76 @@ static void __init kirkwood_legacy_clk_init(void)
> >  	clk_prepare_enable(clk);
> >  }
> >  
> > +#define MV643XX_ETH_MAC_ADDR_LOW	0x0414
> > +#define MV643XX_ETH_MAC_ADDR_HIGH	0x0418
> > +
> > +static void __init kirkwood_dt_eth_fixup(void)
> > +{
> > +	struct device_node *np;
> > +
> > +	/*
> > +	 * The ethernet interfaces forget the MAC address assigned by u-boot
> > +	 * if the clocks are turned off. Usually, u-boot on kirkwood boards
> > +	 * has no DT support to properly set local-mac-address property.
> > +	 * As a workaround, we get the MAC address from mv643xx_eth registers
> > +	 * and update the port device node if no valid MAC address is set.
> > +	 */
> > +	for_each_compatible_node(np, NULL, "marvell,kirkwood-eth-port") {
> > +		struct device_node *pnp = of_get_parent(np);
> > +		struct clk *clk;
> > +		struct property *pmac;
> > +		void __iomem *io;
> > +		u8 *macaddr;
> > +		u32 reg;
> > +
> > +		if (!pnp || !of_device_is_available(pnp))
> > +			continue;
> > +
> > +		clk = of_clk_get(pnp, 0);
> > +		if (!__clk_is_enabled(clk) || of_get_mac_address(np)) {
> 
> Mm.. just as you say this usage of __clk_is_enabled is awkard to say the
> least.
> 
> I'm wondering: is the clock really disabled if the device is not
> available (i.e. status == 'ok')? In other words: isn't the
> !of_device_is_available() test enough?

Well, this stemmed from JasonG's scenario where the second iface is
shut off by the bootloader.  Although one could argue that the
bootloader should then update the dtb to mark that node as disabled...

thx,

Jason.
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