Date:   Sat, 29 Dec 2018 20:25:38 +0100
From:   Andreas Färber <afaerber@...e.de>
To:     Ben Whitten <ben.whitten@...il.com>
Cc:     starnight@...cu.edu.tw, netdev@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org,
        "linux-lpwan@...ts.infradead.org" <linux-lpwan@...ts.infradead.org>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Michael Turquette <mturquette@...libre.com>,
        linux-clk <linux-clk@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>
Subject: Re: [PATCH v3 lora-next 5/5] net: lora: sx125x sx1301: allow radio to
 register as a clk provider

Hi Ben,

+ linux-lpwan, linux-clk, devicetree

Am 12.10.18 um 18:26 schrieb Ben Whitten:
> From: Ben Whitten <ben.whitten@...il.com>
> 
> The 32M is run from the radio, before we just enabled it based on
> the radio number but now we can use the clk framework to request the
> clk is started when we need it.
> 
> The 32M clock produced from the radio is really a gated version of
> tcxo which is a fixed clock provided by hardware, and isn't captured
> in this patch.
> 
> The sx1301 brings the clock up prior to calibration once the radios
> have probed themselves.
> 
> A sample dts showing the clk link:
> 	sx1301: sx1301@0 {

Nit: Node names should not duplicate model from compatible or label.
I've been using "lora" for both concentrator and radios.

> 		...
>                 clocks = <&radio1 0>;

Since you use #clock-cells of zero below, you are specifying two clocks
here, surely unintentional.

>                 clock-names = "clk32m";
> 
>                 radio-spi {
>                         radio0: radio-a@0 {

-a/-b in node names duplicates the unit address. I've been using "lora",
but we might also go for just "radio" or "transceiver"?

>                                 ...
>                         };
> 
>                         radio1: radio-b@1 {

Should add "..." here, too, for clarity.

>                                 #clock-cells = <0>;
>                                 clock-output-names = "clk32m";

Personally I'd reorder those two lines to have #foo-cells last.

But more importantly, in my testing this is lacking, e.g.,
clocks = <&clk32m>;
and an appropriate fixed-clock node in the root node. See inline.

>                         };
>                 };
> 	};

This issue is making me think we should start properly documenting our
dt-bindings in a preceding patch, even if just for my linux-lora staging
tree. Be it in the old .txt format or Rob's newly proposed YAML.

The more cooks are working on SX130x, the better we need to explain what
changes people need to make to their DT to keep things working - if I
stumble as original author, then new testers are even more likely to!

> 
> Signed-off-by: Ben Whitten <ben.whitten@...il.com>
> ---
>  drivers/net/lora/sx125x.c | 112 ++++++++++++++++++++++++++++++++++++++++++----
>  drivers/net/lora/sx1301.c |  13 ++++++
>  drivers/net/lora/sx1301.h |   2 +
>  3 files changed, 119 insertions(+), 8 deletions(-)

In general I'd appreciate if you would prepare, e.g., the clock output
in a preceding sx125x-only patch. Exposing (and consuming) clocks in the
radio driver should be independent of consuming them in the concentrator
driver. That'll make things easier to review for us and also helps avoid
the unusual "sx125x sx1301" in the subject, here and elsewhere.

> 
> diff --git a/drivers/net/lora/sx125x.c b/drivers/net/lora/sx125x.c
> index 36b61b1..b7ca782 100644
> --- a/drivers/net/lora/sx125x.c
> +++ b/drivers/net/lora/sx125x.c
> @@ -9,6 +9,8 @@
>   * Copyright (c) 2013 Semtech-Cycleo
>   */
>  
> +#include <linux/clk.h>
> +#include <linux/clk-provider.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
>  #include <linux/of_device.h>
> @@ -42,10 +44,16 @@ static const struct reg_field sx125x_regmap_fields[] = {
>  };
>  
>  struct sx125x_priv {
> +	struct clk		*clkout;
> +	struct clk_hw		clkout_hw;

The 0-day bots have reported this to break on sparc64, as you've seen.
We'll need to squash a Kconfig or .c based solution here.

> +
> +	struct device		*dev;
>  	struct regmap		*regmap;
>  	struct regmap_field     *regmap_fields[ARRAY_SIZE(sx125x_regmap_fields)];
>  };
>  
> +#define to_clkout(_hw) container_of(_hw, struct sx125x_priv, clkout_hw)
> +
>  static struct regmap_config __maybe_unused sx125x_regmap_config = {
>  	.reg_bits = 8,
>  	.val_bits = 8,
> @@ -64,6 +72,96 @@ static int sx125x_field_write(struct sx125x_priv *priv,
>  	return regmap_field_write(priv->regmap_fields[field_id], val);
>  }
>  
> +static int sx125x_field_read(struct sx125x_priv *priv,
> +		enum sx125x_fields field_id, unsigned int *val)
> +{
> +	return regmap_field_read(priv->regmap_fields[field_id], val);
> +}

Nit: Given how trivial this is, we might make it static inline?

> +
> +static int sx125x_clkout_enable(struct clk_hw *hw)
> +{
> +	struct sx125x_priv *priv = to_clkout(hw);
> +
> +	dev_info(priv->dev, "enabling clkout\n");
> +	return sx125x_field_write(priv, F_CLK_OUT, 1);
> +}
> +
> +static void sx125x_clkout_disable(struct clk_hw *hw)
> +{
> +	struct sx125x_priv *priv = to_clkout(hw);
> +	int ret;
> +
> +	dev_info(priv->dev, "disabling clkout\n");
> +	ret = sx125x_field_write(priv, F_CLK_OUT, 0);
> +	if (ret)
> +		dev_err(priv->dev, "error disabling clkout\n");
> +}
> +
> +static int sx125x_clkout_is_enabled(struct clk_hw *hw)
> +{
> +	struct sx125x_priv *priv = to_clkout(hw);
> +	unsigned int enabled;
> +	int ret;
> +
> +	ret = sx125x_field_read(priv, F_CLK_OUT, &enabled);
> +	if (ret) {
> +		dev_err(priv->dev, "error reading clk enable\n");
> +		return 0;
> +	}
> +	return enabled;
> +}
> +
> +static const struct clk_ops sx125x_clkout_ops = {
> +	.enable = sx125x_clkout_enable,
> +	.disable = sx125x_clkout_disable,
> +	.is_enabled = sx125x_clkout_is_enabled,
> +};
> +
> +static int sx125x_register_clock_provider(struct sx125x_priv *priv)
> +{
> +	struct device *dev = priv->dev;
> +	struct clk_init_data init;
> +	const char *parent;
> +	int ret;
> +
> +	/* Disable CLKOUT */
> +	ret = sx125x_field_write(priv, F_CLK_OUT, 0);
> +	if (ret) {
> +		dev_err(dev, "unable to disable clkout\n");
> +		return ret;
> +	}
> +
> +	/* Register clock provider if expected in DTB */
> +	if (!of_find_property(dev->of_node, "#clock-cells", NULL))
> +		return 0;
> +
> +	dev_info(dev, "registering clkout\n");
> +
> +	parent = of_clk_get_parent_name(dev->of_node, 0);
> +	if (!parent) {
> +		dev_err(dev, "Unable to find parent clk\n");
> +		return -ENODEV;

I got stuck here testing:

[233875.731268] sx1301 spi0.0: SX1301 module probed
[233876.520801] sx1301 spi1.0: SX1301 module probed
[233876.543460] sx125x_con spi0.0-b: SX125x version: 21
[233876.550866] sx125x_con spi0.0-b: registering clkout
[233876.555852] sx125x_con spi0.0-b: Unable to find parent clk
[233876.561491] sx125x_con spi0.0-b: failed to register clkout provider: -19
[233876.569914] sx125x_con spi0.0-a: SX125x version: 21
[233876.582915] sx125x_con spi0.0-a: SX125x module probed
[233876.589100] sx125x_con spi1.0-b: SX125x version: 21
[233876.595981] sx125x_con spi1.0-b: registering clkout
[233876.600986] sx125x_con spi1.0-b: Unable to find parent clk
[233876.606557] sx125x_con spi1.0-b: failed to register clkout provider: -19
[233876.614559] sx125x_con spi1.0-a: SX125x version: 21
[233876.625047] sx125x_con spi1.0-a: SX125x module probed

Your DT example above does not use any parent clock for the radios. It
seems adding any clocks = <> reference helps resolve that error.

I don't spot any code dealing with enabling that parent either. With a
fixed-clock we appear to get around that, except for reference counting:

# cat /sys/kernel/debug/clk/clk_summary
[...]
 rak831-clk32m                        0        0        0    32000000
       0     0  50000
    rak831_clk32m                     0        0        0    32000000
       0     0  50000
 rg186-clk32m                         0        0        0    32000000
       0     0  50000
    rg186_clk32m                      0        0        0    32000000
       0     0  50000

But it might just as well be a gpio-gate-clock or some PMIC providing
it, needing prepare+enable ops.

> +	}
> +
> +	init.ops = &sx125x_clkout_ops;
> +	init.flags = CLK_IS_BASIC;

I don't think that's really true.

> +	init.parent_names = &parent;
> +	init.num_parents = 1;
> +	priv->clkout_hw.init = &init;
> +
> +	of_property_read_string_index(dev->of_node, "clock-output-names", 0,
> +			&init.name);

Error handling for this was in your style cleanup patch. I'd prefer to
squash that hunk here.

However, clock-output-names is documented as an optional property, so we
shouldn't rely on it here, please.

> +
> +	priv->clkout = devm_clk_register(dev, &priv->clkout_hw);
> +	if (IS_ERR(priv->clkout)) {
> +		dev_err(dev, "failed to register clkout\n");

Would be nice to output the error code, but then again the caller does.

> +		return PTR_ERR(priv->clkout);
> +	}
> +	ret = of_clk_add_hw_provider(dev->of_node, of_clk_hw_simple_get,
> +			&priv->clkout_hw);


Don't we need to unregister the provider on remove? Using the devm_
variant would seem to handle that for us.

> +	return ret;
> +}

I wonder whether we may want to split (some of) this off into a _clk.c
for Makefile-based optional compilation? We could then provide a static
inline version of sx125x_register_clock_provider() as alternative and
have this file not care.

> +
>  static int __maybe_unused sx125x_regmap_probe(struct device *dev, struct regmap *regmap, unsigned int radio)
>  {
>  	struct sx125x_priv *priv;
> @@ -76,6 +174,7 @@ static int __maybe_unused sx125x_regmap_probe(struct device *dev, struct regmap
>  		return -ENOMEM;
>  
>  	dev_set_drvdata(dev, priv);
> +	priv->dev = dev;
>  	priv->regmap = regmap;
>  	for (i = 0; i < ARRAY_SIZE(sx125x_regmap_fields); i++) {
>  		const struct reg_field *reg_fields = sx125x_regmap_fields;
> @@ -99,16 +198,13 @@ static int __maybe_unused sx125x_regmap_probe(struct device *dev, struct regmap
>  		dev_info(dev, "SX125x version: %02x\n", val);
>  	}
>  
> -	if (radio == 1) { /* HACK */
> -		ret = sx125x_field_write(priv, F_CLK_OUT, 1);
> -		if (ret) {
> -			dev_err(dev, "enabling clock output failed\n");
> -			return ret;
> -		}
> -
> -		dev_info(dev, "enabling clock output\n");
> +	ret = sx125x_register_clock_provider(priv);
> +	if (ret) {
> +		dev_err(dev, "failed to register clkout provider: %d\n", ret);
> +		return ret;
>  	}
>  
> +	/* TODO Only needs setting on radio on the TX path */

Slightly unrelated, but thanks for documenting. :)

>  	ret = sx125x_field_write(priv, F_TX_DAC_CLK_SEL, 1);
>  	if (ret) {
>  		dev_err(dev, "clock select failed\n");
> diff --git a/drivers/net/lora/sx1301.c b/drivers/net/lora/sx1301.c
> index 339f8d9..23cbddc3 100644
> --- a/drivers/net/lora/sx1301.c
> +++ b/drivers/net/lora/sx1301.c
> @@ -10,6 +10,7 @@
>   */
>  
>  #include <linux/bitops.h>
> +#include <linux/clk.h>
>  #include <linux/delay.h>
>  #include <linux/firmware.h>
>  #include <linux/lora.h>
> @@ -378,6 +379,18 @@ static int sx130x_loradev_open(struct net_device *netdev)
>  		return -ENXIO;
>  	}
>  
> +	priv->clk32m = devm_clk_get(priv->dev, "clk32m");
> +	if (IS_ERR(priv->clk32m)) {
> +		dev_err(priv->dev, "failed to get clk32m\n");
> +		return PTR_ERR(priv->clk32m);
> +	}
> +
> +	ret = clk_prepare_enable(priv->clk32m);

Does this cope with an absent/NULL clock?

> +	if (ret) {
> +		dev_err(priv->dev, "failed to enable clk32m: %d\n", ret);
> +		return ret;
> +	}
> +
>  	ret = sx1301_field_write(priv, F_GLOBAL_EN, 1);
>  	if (ret) {
>  		dev_err(priv->dev, "enable global clocks failed\n");
> diff --git a/drivers/net/lora/sx1301.h b/drivers/net/lora/sx1301.h
> index 0bbd948..a1a2e38 100644
> --- a/drivers/net/lora/sx1301.h
> +++ b/drivers/net/lora/sx1301.h
> @@ -9,6 +9,7 @@
>  #ifndef _SX1301_
>  #define _SX1301_
>  
> +#include <linux/clk.h>
>  #include <linux/regmap.h>
>  #include <linux/gpio/consumer.h>
>  #include <linux/lora/dev.h>
> @@ -108,6 +109,7 @@ static const struct reg_field sx1301_regmap_fields[] = {
>  struct sx1301_priv {
>  	struct lora_dev_priv lora;
>  	struct device		*dev;
> +	struct clk		*clk32m;
>  	struct gpio_desc *rst_gpio;
>  	struct regmap		*regmap;
>  	struct regmap_field     *regmap_fields[ARRAY_SIZE(sx1301_regmap_fields)];

Thanks again for contributing this cleanup series!
(already staged in linux-lora.git)

Regards,
Andreas

-- 
SUSE Linux GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)

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