[PATCH V3 0/3] clk: introduce clk_bulk_get accessories

[Dong Aisheng]

These helper function allows drivers to get several clk consumers in
one operation.  If any of the clk cannot be acquired then any clks
that were got will be put before returning to the caller.

The idea firstly came out when i wanted to clean up and optimize
imx6q-cpufreq driver which needs to handle a lot of clocks as it
becomes a bit mess.

e.g. drivers/cpufreq/imx6q-cpufreq.c

You will see we need get 7 clocks during driver probe.
(Add there will be more, e.g. pll1, pll1_bypass, pll1_bypass_src,
in the future when adding busfreq support).

static int imx6q_cpufreq_probe(struct platform_device *pdev)
{
....
	arm_clk = clk_get(cpu_dev, "arm");
	pll1_sys_clk = clk_get(cpu_dev, "pll1_sys");
	pll1_sw_clk = clk_get(cpu_dev, "pll1_sw");
	step_clk = clk_get(cpu_dev, "step");
	pll2_pfd2_396m_clk = clk_get(cpu_dev, "pll2_pfd2_396m");
	if (IS_ERR(arm_clk) || IS_ERR(pll1_sys_clk) || IS_ERR(pll1_sw_clk) ||
	    IS_ERR(step_clk) || IS_ERR(pll2_pfd2_396m_clk)) {
		dev_err(cpu_dev, "failed to get clocks\n");
		ret = -ENOENT;
		goto put_clk;
	}

	if (of_machine_is_compatible("fsl,imx6ul")) {
		pll2_bus_clk = clk_get(cpu_dev, "pll2_bus");
		secondary_sel_clk = clk_get(cpu_dev, "secondary_sel");
		if (IS_ERR(pll2_bus_clk) || IS_ERR(secondary_sel_clk)) {
			dev_err(cpu_dev, "failed to get clocks specific to imx6ul\n");
			ret = -ENOENT;
			goto put_clk;
		}
	}
....
put_clk: 
        if (!IS_ERR(arm_clk))
                clk_put(arm_clk);
        if (!IS_ERR(pll1_sys_clk))
                clk_put(pll1_sys_clk);
	...........
}

Together with the err path handling for each clocks, it does make
things a bit ugly.

Since we already have regulator_bulk_get accessories, i thought we
probably could introduce clk_bulk_get as well to handle such case to
ease the driver owners' life. 

Besides IMX cpufreq driver, there is also some similar cases
in kernel which could befinit from this api as well.
e.g.
drivers/cpufreq/tegra124-cpufreq.c
drivers/cpufreq/s3c2412-cpufreq.c
sound/soc/samsung/smdk_spdif.c
arch/arm/mach-omap1/serial.c
...

And actually, if we handle clocks more than 3, then it might be
worthy to try, which there is quite many manay in kernel and
that probably could save a lot codes.

Comments are welcome and appreciated!

Tested on MX6Q SabreSD board with CPUfreq stress.
Also ran IA64 and m68k compiling test:
make.cross ARCH=m68k 
make.cross ARCH=ia64

ChangeLog:
v2->v3:
 Only Patch 1 changed.
 * release resource in reversed order in case an error according to
   Geert Uytterhoeven's suggestion

v1->v2:
 * Most significant change is introducing clk-bulk.c to centrally
   handle bulk_clks and fix !CONFIG_CLKDEV_LOOKUP platforms build break.
   Other are comments fix, adding const annotation and etc.
   Refer to individual patches for details.

[v1] https://lkml.org/lkml/2017/4/11/335
[v2] https://lkml.org/lkml/2017/5/8/276

Dong Aisheng (3):
  clk: add clk_bulk_get accessories
  clk: add managed version of clk_bulk_get
  cpufreq: imx6q: refine clk operations

 drivers/clk/Makefile            |   2 +-
 drivers/clk/clk-bulk.c          | 157 ++++++++++++++++++++++++++++++++++++++++
 drivers/clk/clk-devres.c        |  36 +++++++++
 drivers/cpufreq/imx6q-cpufreq.c | 119 ++++++++++++++----------------
 include/linux/clk.h             | 132 +++++++++++++++++++++++++++++++++
 5 files changed, 379 insertions(+), 67 deletions(-)
 create mode 100644 drivers/clk/clk-bulk.c

-- 
2.7.4