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

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Date:	Thu, 3 Oct 2013 16:02:02 -0300
From:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
To:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Cc:	Jason Cooper <jason@...edaemon.net>, 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 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?

Or maybe I'm missing something?
-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
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