Re: [PATCH 2/5] ASoC: madera: Add common support for Cirrus Logic Madera codecs

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On 24/05/19 15:56, Mark Brown wrote:
On Fri, May 24, 2019 at 11:41:55AM +0100, Charles Keepax wrote:

+	/*
+	 * Just read a register a few times to ensure the internal
+	 * oscillator sends out a few clocks.
+	 */
+	for (i = 0; i < 4; i++) {
+		ret = regmap_read(madera->regmap, MADERA_SOFTWARE_RESET, &val);
+		if (ret)
+			dev_err(madera->dev,
+				"%s Failed to read register: %d (%d)\n",
+				__func__, ret, i);

Why use %s to format the __func__ rather than just concatenate?

GCC docs say that it's a magic variable so cannot be concatenated with string literals. Though I
never tried concatenation to see if it works.


+	}
+
+	udelay(300);

So we read the register a few times then add a few hundred us of delay
after?  Surely that delay is going to be negligable compared to the time
spent on I/O?

The register reads are to create clock cycles in the silicon, not to generate delay.


+int madera_sysclk_ev(struct snd_soc_dapm_widget *w,
+		     struct snd_kcontrol *kcontrol, int event)
+{
+	struct snd_soc_component *component = snd_soc_dapm_to_component(w->dapm);
+	struct madera_priv *priv = snd_soc_component_get_drvdata(component);
+
+	madera_spin_sysclk(priv);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(madera_sysclk_ev);

This will delay both before and after every power up and power down.
Are you sure that makes sense?


I think that's correct but we can re-check with hardware people. It's not just a delay,
it needs to ensure there are always a certain number of SYSCLK cycles in the hardware to
avoid leaving certain state machines in limbo.

+
+	ret = madera_check_speaker_overheat(madera, &warn, &shutdown);
+	if (ret)
+		shutdown = true; /* for safety attempt to shutdown on error */
+
+	if (shutdown) {
+		dev_crit(madera->dev, "Thermal shutdown\n");
+		ret = regmap_update_bits(madera->regmap,
+					 MADERA_OUTPUT_ENABLES_1,
+					 MADERA_OUT4L_ENA |
+					 MADERA_OUT4R_ENA, 0);
+		if (ret != 0)
+			dev_crit(madera->dev,
+				 "Failed to disable speaker outputs: %d\n",
+				 ret);
+	} else if (warn) {
+		dev_crit(madera->dev, "Thermal warning\n");
+	}
+
+	return IRQ_HANDLED;

We will flag the interrupt as handled if there was neither a warning nor
a critical overheat?  I'd expect some warning about a spurious interrupt
at least.

+static int madera_get_variable_u32_array(struct madera_priv *priv,
+					 const char *propname,
+					 u32 *dest,
+					 int n_max,
+					 int multiple)
+{
+	struct madera *madera = priv->madera;
+	int n, ret;
+
+	n = device_property_read_u32_array(madera->dev, propname, NULL, 0);
+	if (n == -EINVAL) {
+		return 0;	/* missing, ignore */
+	} else if (n < 0) {
+		dev_warn(madera->dev, "%s malformed (%d)\n",
+			 propname, n);
+		return n;
+	} else if ((n % multiple) != 0) {
+		dev_warn(madera->dev, "%s not a multiple of %d entries\n",
+			 propname, multiple);
+		return -EINVAL;
+	}
+
+	if (n > n_max)
+		n = n_max;
+
+	ret = device_property_read_u32_array(madera->dev, propname, dest, n);
+
+	if (ret < 0)
+		return ret;
+	else
+		return n;
+}

This feels like it should perhaps be a generic OF helper function -
there's nothing driver specific I'm seeing here and arrays that need to
be a multiple of N entries aren't that uncommon I think.

+	mutex_lock(&priv->rate_lock);
+	cached_rate = priv->adsp_rate_cache[adsp_num];
+	mutex_unlock(&priv->rate_lock);

What's this lock protecting?  The value can we read can change as soon
as the lock is released and we're just reading a single word here rather
than traversing a data structure that might change under us or
something.

+void madera_destroy_bus_error_irq(struct madera_priv *priv, int dsp_num)
+{
+	struct madera *madera = priv->madera;
+
+	madera_free_irq(madera,
+			madera_dsp_bus_error_irqs[dsp_num],
+			&priv->adsp[dsp_num]);
+}
+EXPORT_SYMBOL_GPL(madera_destroy_bus_error_irq);

We use free rather than destroy normally?

+static const char * const madera_dfc_width_text[MADERA_DFC_WIDTH_ENUM_SIZE] = {
+	"8bit", "16bit", "20bit", "24bit", "32bit",
+};

Spaces might make these more readable.

+static void madera_sleep(unsigned int delay)
+{
+	if (delay < 20) {
+		delay *= 1000;
+		usleep_range(delay, delay + 500);
+	} else {
+		msleep(delay);
+	}
+}

This feels like it might make sense as a helper function as well - I
could've sworn there was one already but I can't immediately find it.





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