Quoting Stephen Boyd (2014-01-08 18:11:40)

On 01/08/14 17:51, Mike Turquette wrote:

quoted

Quoting Stephen Boyd (2013-12-23 17:12:26)

quoted

Add support to the clock core so that drivers can pass in a
regmap. If no regmap is specified try to query the device that's
registering the clock for its regmap. This should allow drivers
to use the core regmap helpers. This is based on a similar design
in the regulator framework.

Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Stephen Boyd <redacted>
---
 drivers/clk/clk.c            | 8 ++++++++
 include/linux/clk-provider.h | 7 +++++++
 2 files changed, 15 insertions(+)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 9ad7b71..5e71f5c 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c

@@ -20,6 +20,7 @@
 #include <linux/device.h>
 #include <linux/init.h>
 #include <linux/sched.h>
+#include <linux/regmap.h>
 
 static DEFINE_SPINLOCK(enable_lock);
 static DEFINE_MUTEX(prepare_lock);

@@ -1834,6 +1835,13 @@ static int _clk_register(struct device *dev, struct clk_hw *hw, struct clk *clk)
        clk->num_parents = hw->init->num_parents;
        hw->clk = clk;
 
+       if (hw->init->regmap)
+               hw->regmap = hw->init->regmap;

Hi Stephen,

The whole series looks good to me except for the placement of the regmap
details inside struct clk_hw. That structure exists only to hide struct
clk from the hardware-specific clock structure and I'd not like to set
the precedent of shoving per-clock data into it.

As an alternative, how about finding a way to put these per-clock regmap
details into the hardware-specific clock structure? I understand that
you want to make these ops available to others, which is why they are in
the public struct clk_hw. I'm just wondering if that is the right way to
do it...

The regulator framework has gone this way. It seemed like a similar
approach in the clock framework would be the right way to go too.

quoted

Patch #3 illustrates the sort of struct-member-creep that worries me.
What is to stop someone from putting "unsigned int divider_reg" or
"unsigned int mux_reg", and then the thing just keeps growing.

I see two ways forward if you don't want these members in struct clk_hw.

1) Inheritance: struct clk_regmap wrapper struct and
clk_register_regmap() and devm_clk_register_regmap() and then another
wrapper struct around that.

 example:

struct clk_regmap {
        struct clk_hw hw;
        struct regmap *regmap;
        unsigned int enable_reg;
        unsigned int enable_mask;
        bool enable_is_inverted;
};

struct clk_branch {
        u32     hwcg_reg;
        u32     halt_reg;
        u8      hwcg_bit;
        u8      halt_bit;
        u8      halt_check;

        struct clk_regmap       clkr;
};

static struct clk_branch gsbi1_uart_clk = {
        .halt_reg = 0x2fcc,
        .halt_bit = 10,
        .clkr = {
                .enable_reg = 0x29d4,
                .enable_mask = BIT(9),
                .hw.init = &(struct clk_init_data){
                        .name = "gsbi1_uart_clk",
                        .parent_names = (const char *[]){
                                "gsbi1_uart_src",
                        },
                        .num_parents = 1,
                        .ops = &clk_branch_ops,
                        .flags = CLK_SET_RATE_PARENT,
                },
        },
};

If we're going to use these wrappers, why make it regmap specific? The
struct clk_desc patches[1][2] can achieve this, but in a more generic
way.

2) Interfaces: Add a void *data in struct clk_hw that can point to
whatever I want and still have the same clk_regmap_register() and
devm_clk_regmap_register()

Example:

struct clk_hw {
        struct clk *clk;
        const struct clk_init_data *init;
        void *data;
};

struct clk_regmap {
        struct regmap *regmap;
        unsigned int enable_reg;
        unsigned int enable_mask;
        bool enable_is_inverted;
};

struct clk_branch {
        u32     hwcg_reg;
        u32     halt_reg;
        u8      hwcg_bit;
        u8      halt_bit;
        u8      halt_check;

        struct clk_hw;
};

static struct clk_branch gsbi1_uart_clk = {
        .halt_reg = 0x2fcc,
        .halt_bit = 10,
        .hw = {
                .data = &(struct clk_regmap){
                        .enable_reg = 0x29d4,
                        .enable_mask = BIT(9),
                 };
                .init = &(struct clk_init_data){
                        .name = "gsbi1_uart_clk",
                        .parent_names = (const char *[]){
                                "gsbi1_uart_src",
                        },
                        .num_parents = 1,
                        .ops = &clk_branch_ops,
                        .flags = CLK_SET_RATE_PARENT,
                },
        },
};

I guess option 2 is less likely given your comment about clk_hw being
nothing more than a traversal mechanism.

Instead of private data, how about a .register() callback function that
can point to anything you like? The clk_desc patches implement this and
it would suffice for registering regmap ops or anything else, without
polluting struct clk_hw.

[1] http://www.spinics.net/lists/linux-omap/msg101822.html
[2] http://www.spinics.net/lists/linux-omap/msg101698.html

So you could statically define gsbi1_uart_clk with:

static struct clk_branch_desc gsbi1_uart_clk_desc = {
	.halt_reg = 0x2fcc,
	.halt_bit = 10,
	.enable_reg = 0x29d4,
	.enable_mask = BIT(9),
	.desc = {
		.name = "gsbi1_uart_clk",
		.parent_names = (const char *[]){
			"gsbi1_uart_src",
		},
		.num_parents = 1,
		.ops = &clk_branch_ops,
		.flags = CLK_SET_RATE_PARENT,
	},
};

And then register it with:

clk_register_desc(NULL, &gsbi1_uart_clk_desc.desc);

This is very analogous to the way that you use use &gsbi1_uart_clk.hw
but it is more generic and also doesn't pollute clk_hw any further. I
also think your static data is quite a bit prettier using this method.

Thoughts?

Regards,
Mike

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