Re: [alsa-devel] [PATCH v3 3/9] clk: at91: add audio pll clock drivers

Hi Stephen,

On 22/07/2017 00:20, Stephen Boyd wrote:

On 07/13, Quentin Schulz wrote:

...

diff --git a/drivers/clk/at91/clk-audio-pll-pad.c b/drivers/clk/at91/clk-audio-pll-pad.c new file mode 100644 index 000000000000..10dd6d625696 --- /dev/null +++ b/drivers/clk/at91/clk-audio-pll-pad.c @@ -0,0 +1,206 @@ +/*

• • Copyright (C) 2016 Atmel Corporation,

• •                 Nicolas Ferre <nicolas.ferre@atmel.com>
    

• • Copyright (C) 2017 Free Electrons,

• •        Quentin Schulz <quentin.schulz@free-electrons.com>
    

• • This program is free software; you can redistribute it and/or modify
• • it under the terms of the GNU General Public License as published by
• • the Free Software Foundation; either version 2 of the License, or
• • (at your option) any later version.
• */

+#include <linux/clk.h> +#include <linux/clk-provider.h> +#include <linux/clkdev.h>

Used?

Not really, I need slab.h for kzalloc tough which was included by clkdev.

[...]

...

+static int clk_audio_pll_pad_set_rate(struct clk_hw *hw, unsigned long rate,

• 		      unsigned long parent_rate)
  

+{

• struct clk_audio_pad *apad_ck = to_clk_audio_pad(hw);
• u8 tmp_div;
• pr_debug("A PLL/PAD: %s, rate = %lu (parent_rate = %lu)\n", __func__,

•  rate, parent_rate);
  

• if (!rate)

• return -EINVAL;
  

This happens?

I don't know, but it's better to do this quick check rather than being exposed to a division by zero IMHO. Nothing in clk_ops states that the rate given to set_rate is non-zero, so I made sure this can't happen.

...

• tmp_div = parent_rate / rate;
• if (tmp_div % 3 == 0) {

• apad_ck->qdaudio = tmp_div / 3;
  

• apad_ck->div = 3;
  

• } else {

• apad_ck->qdaudio = tmp_div / 2;
  

• apad_ck->div = 2;
  

• }[...]

+static void __init of_sama5d2_clk_audio_pll_pad_setup(struct device_node *np) +{

• struct clk_audio_pad *apad_ck;
• struct clk_init_data init;

Best to initialize to { } just in case we add something later.

ACK.

...

• struct regmap *regmap;
• const char *parent_name;
• const char *name = np->name;
• int ret;
• parent_name = of_clk_get_parent_name(np, 0);
• of_property_read_string(np, "clock-output-names", &name);
• regmap = syscon_node_to_regmap(of_get_parent(np));
• if (IS_ERR(regmap))

• return;
  

• apad_ck = kzalloc(sizeof(*apad_ck), GFP_KERNEL);
• if (!apad_ck)

• return;
  

• init.name = name;
• init.ops = &audio_pll_pad_ops;
• init.parent_names = (parent_name ? &parent_name : NULL);

Use of_clk_parent_fill()?

[Deleting `parent_name = of_clk_get_parent_name(np, 0);`] [Deleting `init.parent_names = (parent_name ? &parent_name : NULL);`]

+ const char *parent_names[1]; [...] + of_clk_parent_fill(np, parent_names, 1); + init.parent_names = parent_names;

Is it what you're asking?

...

• init.num_parents = 1;
• init.flags = CLK_SET_RATE_GATE | CLK_SET_PARENT_GATE |

• CLK_SET_RATE_PARENT;
  

• apad_ck->hw.init = &init;
• apad_ck->regmap = regmap;
• ret = clk_hw_register(NULL, &apad_ck->hw);
• if (ret)

• kfree(apad_ck);
  

• else

• of_clk_add_hw_provider(np, of_clk_hw_simple_get, &apad_ck->hw);
  

Maybe we should make this register sequence a helper function. Seems common.

I can put such an helper in an header if this is what you meant.

...

+}

+CLK_OF_DECLARE(of_sama5d2_clk_audio_pll_pad_setup,

•       "atmel,sama5d2-clk-audio-pll-pad",
  

•       of_sama5d2_clk_audio_pll_pad_setup);
  

We can't have a device driver for this?

Could you elaborate please?

...

diff --git a/drivers/clk/at91/clk-audio-pll-pmc.c b/drivers/clk/at91/clk-audio-pll-pmc.c new file mode 100644 index 000000000000..7b0847ed7a4b --- /dev/null +++ b/drivers/clk/at91/clk-audio-pll-pmc.c

[...]

...

+static int clk_audio_pll_pmc_set_rate(struct clk_hw *hw, unsigned long rate,

• 		      unsigned long parent_rate)
  

+{

• struct clk_audio_pmc *apmc_ck = to_clk_audio_pmc(hw);
• if (!rate)

• return -EINVAL;
  

• pr_debug("A PLL/PMC: %s, rate = %lu (parent_rate = %lu)\n", __func__,

•  rate, parent_rate);
  

• apmc_ck->qdpmc = parent_rate / rate - 1;

Hopefully rate isn't 1 or that goes undefined.

Thanks to operator precedence, the only check to do is rate != 0 (done few lines above). Division has precedence over substraction.

[...]

...

+static void __init of_sama5d2_clk_audio_pll_pmc_setup(struct device_node *np) +{

• struct clk_audio_pmc *apmc_ck;
• struct clk_init_data init;
• struct regmap *regmap;
• const char *parent_name;
• const char *name = np->name;
• int ret;
• parent_name = of_clk_get_parent_name(np, 0);
• of_property_read_string(np, "clock-output-names", &name);
• regmap = syscon_node_to_regmap(of_get_parent(np));
• if (IS_ERR(regmap))

• return;
  

• apmc_ck = kzalloc(sizeof(*apmc_ck), GFP_KERNEL);
• if (!apmc_ck)

• return;
  

• init.name = name;
• init.ops = &audio_pll_pmc_ops;
• init.parent_names = (parent_name ? &parent_name : NULL);

This feels repetitive.

...

• init.num_parents = 1;
• init.flags = CLK_SET_RATE_GATE | CLK_SET_PARENT_GATE |

• CLK_SET_RATE_PARENT;
  

• apmc_ck->hw.init = &init;
• apmc_ck->regmap = regmap;
• ret = clk_hw_register(NULL, &apmc_ck->hw);
• if (ret)

• kfree(apmc_ck);
  

• else

• of_clk_add_hw_provider(np, of_clk_hw_simple_get, &apmc_ck->hw);
  

+}

+CLK_OF_DECLARE(of_sama5d2_clk_audio_pll_pmc_setup,

•       "atmel,sama5d2-clk-audio-pll-pmc",
  

•       of_sama5d2_clk_audio_pll_pmc_setup);
  

Very

Basically, both share almost the same code but have different formulae for the rate.

...

diff --git a/drivers/clk/at91/clk-audio-pll.c b/drivers/clk/at91/clk-audio-pll.c new file mode 100644 index 000000000000..efc2cb58da85 --- /dev/null +++ b/drivers/clk/at91/clk-audio-pll.c

[...]

...

+static unsigned long clk_audio_pll_fout(unsigned long parent_rate,

• 			unsigned long nd, unsigned long fracr)
  

+{

• unsigned long long fr = (unsigned long long)parent_rate *

• 				(unsigned long long)fracr;
  

We only need one cast here?

Indeed, I'll remove the casting of fracr.

[...]

...

+static long clk_audio_pll_round_rate(struct clk_hw *hw, unsigned long rate,

• 		     unsigned long *parent_rate)
  

+{

• long best_rate = -EINVAL;
• unsigned long fracr, nd;
• int ret;
• pr_debug("A PLL: %s, rate = %lu (parent_rate = %lu)\n", __func__, rate,

•  *parent_rate);
  

• if (rate < AUDIO_PLL_FOUT_MIN)

• rate = AUDIO_PLL_FOUT_MIN;
  

• else if (rate > AUDIO_PLL_FOUT_MAX)

• rate = AUDIO_PLL_FOUT_MAX;
  

Use clamp. Also, did you want to use determine_rate callback and clamp the requested rate range?

Didn't know this one, thanks!

I want determine_rate to return a valid rate for the pll so I clamp the requested rate range in this one. In set_rate, I just tell the user that any requested rate outside of the valid range is invalid. Does that answer your question?

[...]

...

+static void __init of_sama5d2_clk_audio_pll_setup(struct device_node *np) +{

• struct clk_audio_frac *fck;
• struct clk_init_data init;
• struct regmap *regmap;
• const char *parent_name;
• const char *name = np->name;
• int ret;
• parent_name = of_clk_get_parent_name(np, 0);
• of_property_read_string(np, "clock-output-names", &name);

Any way to not rely on clock-output-names?

I guess we could use the name of the DT node (as it's done in the variable initialization block above) and not override it by clock-output-names?

...

• regmap = syscon_node_to_regmap(of_get_parent(np));
• if (IS_ERR(regmap))

• return;
  

• fck = kzalloc(sizeof(*fck), GFP_KERNEL);

This variable name looks like f*ck, perhaps name it something else. frac?

Sure.

[...]

Thanks, Quentin