linux-kernel - Re: [PATCH v5 3/4] clk: introduce the common clock framework

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Message-ID: <20120309075720.GC16608@lunn.ch>
Date:	Fri, 9 Mar 2012 08:57:20 +0100
From:	Andrew Lunn <andrew@...n.ch>
To:	Sascha Hauer <s.hauer@...gutronix.de>
Cc:	"Turquette, Mike" <mturquette@...com>,
	Andrew Lunn <andrew@...n.ch>, Paul Walmsley <paul@...an.com>,
	linaro-dev@...ts.linaro.org,
	Linus Walleij <linus.walleij@...ricsson.com>,
	patches@...aro.org, Stephen Boyd <sboyd@...eaurora.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Magnus Damm <magnus.damm@...il.com>,
	linux-kernel@...r.kernel.org,
	Rob Herring <rob.herring@...xeda.com>,
	Richard Zhao <richard.zhao@...aro.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Deepak Saxena <dsaxena@...aro.org>,
	Saravana Kannan <skannan@...eaurora.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Shawn Guo <shawn.guo@...escale.com>,
	Amit Kucheria <amit.kucheria@...aro.org>,
	Russell King <linux@....linux.org.uk>,
	Jeremy Kerr <jeremy.kerr@...onical.com>,
	Arnd Bergman <arnd.bergmann@...aro.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v5 3/4] clk: introduce the common clock framework

> I'd say use the nonstatic ones. I think using the static initializers
> will cause us much pain in the future. I've been through several rebases
> on the i.MX clock rework and everytime I wish my sed foo would be
> better. Now imagine what happens when it turns out that the internal
> struct clk layout or the structs for the muxes/dividers/gates have to
> be changed.

/*****************************************************************************
 * CLK tree
 ****************************************************************************/
static DEFINE_SPINLOCK(gating_lock);

#define DEFINE_KIRKWOOD_CLK_GATE(_name, _bit)                           \
        DEFINE_CLK_GATE(_name, "tclk", NULL, 0,                         \
                        (void __iomem *)CLOCK_GATING_CTRL,              \
                        _bit, 0, &gating_lock)

DEFINE_KIRKWOOD_CLK_GATE(clk_ge0,    CGC_BIT_GE0);
DEFINE_KIRKWOOD_CLK_GATE(clk_pex0,   CGC_BIT_PEX0);
DEFINE_KIRKWOOD_CLK_GATE(clk_usb0,   CGC_BIT_USB0);
DEFINE_KIRKWOOD_CLK_GATE(clk_sdio,   CGC_BIT_SDIO);
DEFINE_KIRKWOOD_CLK_GATE(clk_tsu,    CGC_BIT_TSU);
DEFINE_KIRKWOOD_CLK_GATE(clk_dunit,  CGC_BIT_DUNIT);
DEFINE_KIRKWOOD_CLK_GATE(clk_runit,  CGC_BIT_RUNIT);

I've so far not had any problems, and not needed an sed foo.  I do
only have a dozen or so clocks, which helps. But even so, all the real
pain is hidden inside DEFINE_CLK_GATE() which Mike maintains.

I guess the problem comes when you are not using the basic clk
providers, but your own provider. What might help is if
linux/clk-provider.h could provide some macros to do most of the
generic definitions. Something like:

#define DEFINE_CLK_GENERIC(_name, _flags, _ops)                 \
        static struct clk _name;                                \
        static char *_name##_parent_names[] = {};               \
        static struct clk _name = {                             \
                .name = #_name,                                 \
                .ops = &_ops,                                   \
                .hw = &_name##_hw.hw,                           \
                .parent_names = _name##_parent_names,           \
                .num_parents =                                  \
                        ARRAY_SIZE(_name##_parent_names),       \
                .flags = _flags,                                \
        };

and then you have something like

#define DEFINE_CLK_IMX(_name, _flags, _foo, _bar)               \
        static struct clk_imx _name##_hw = {                    \
                .hw = {                                         \
                        .clk = &_name,                          \
                },                                              \
                .foo = _foo,                                    \
                .bar = _bar,                                    \
        };                                                      \
	DEFINE_CLK_GENERIC(_name, _flags, clk_imx_ops)           

	Andrew
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