Subject: [PATCH 1/2] [v5] pinctrl: qcom: disable GPIO groups with no pins

From: [email-masked] (Timur Tabi)
Date: Thu, 7 Sep 2017 10:33:28 -0500

pinctrl-msm only accepts an array of GPIOs from 0 to n-1, and it expects
each group to support have only one pin (npins == 1).

We can support "sparse" GPIO maps if we allow for some groups to have zero
pins (npins == 0).  These pins are "hidden" from the rest of the driver
and gpiolib.

A new boolean 'sparse' indicates whether the GPIO map is sparse.  If any
GPIO has an 'npins' value of 0, then 'sparse' must be set to True.

Most access to unavailable GPIOs can be blocked via the gpio_chip.request
function.  The one exception is when gpiochip_add_data() scans all of
the GPIOs without "requesting" them.  To cover this case,
msm_gpio_get_direction() separately checks if the GPIO is available.

Signed-off-by: Timur Tabi <[email-masked]>
---
 drivers/pinctrl/qcom/pinctrl-msm.c | 110 +++++++++++++++++++++++++++++++++++--
 drivers/pinctrl/qcom/pinctrl-msm.h |   2 +
 2 files changed, 106 insertions(+), 6 deletions(-)

diff --git a/drivers/pinctrl/qcom/pinctrl-msm.c b/drivers/pinctrl/qcom/pinctrl-msm.c
index ff491da64dab..ca4ae3d76eb4 100644
--- a/drivers/pinctrl/qcom/pinctrl-msm.c
+++ b/drivers/pinctrl/qcom/pinctrl-msm.c
@@ -443,6 +443,14 @@ static int msm_gpio_get_direction(struct gpio_chip *chip, unsigned int offset)
 
 	g = &pctrl->soc->groups[offset];
 
+	/*
+	 * During initialization, gpiolib may query all GPIOs for their
+	 * initial direction, regardless if they exist, so block access
+	 * to those that are unavailable.
+	 */
+	if (!g->npins)
+		return -ENODEV;
+
 	val = readl(pctrl->regs + g->ctl_reg);
 
 	/* 0 = output, 1 = input */
@@ -507,6 +515,11 @@ static void msm_gpio_dbg_show_one(struct seq_file *s,
 	};
 
 	g = &pctrl->soc->groups[offset];
+
+	/* If the GPIO group has no pins, then don't show it. */
+	if (!g->npins)
+		return;
+
 	ctl_reg = readl(pctrl->regs + g->ctl_reg);
 
 	is_out = !!(ctl_reg & BIT(g->oe_bit));
@@ -516,7 +529,7 @@ static void msm_gpio_dbg_show_one(struct seq_file *s,
 
 	seq_printf(s, " %-8s: %-3s %d", g->name, is_out ? "out" : "in", func);
 	seq_printf(s, " %dmA", msm_regval_to_drive(drive));
-	seq_printf(s, " %s", pulls[pull]);
+	seq_printf(s, " %s\n", pulls[pull]);
 }
 
 static void msm_gpio_dbg_show(struct seq_file *s, struct gpio_chip *chip)
@@ -524,23 +537,36 @@ static void msm_gpio_dbg_show(struct seq_file *s, struct gpio_chip *chip)
 	unsigned gpio = chip->base;
 	unsigned i;
 
-	for (i = 0; i < chip->ngpio; i++, gpio++) {
+	for (i = 0; i < chip->ngpio; i++, gpio++)
 		msm_gpio_dbg_show_one(s, NULL, chip, i, gpio);
-		seq_puts(s, "\n");
-	}
 }
 
 #else
 #define msm_gpio_dbg_show NULL
 #endif
 
+/*
+ * If the requested GPIO has no pins, then treat it as unavailable.
+ * Otherwise, call the standard request function.
+ */
+static int msm_gpio_request(struct gpio_chip *chip, unsigned int offset)
+{
+	struct msm_pinctrl *pctrl = gpiochip_get_data(chip);
+	const struct msm_pingroup *g = &pctrl->soc->groups[offset];
+
+	if (!g->npins)
+		return -ENODEV;
+
+	return gpiochip_generic_request(chip, offset);
+}
+
 static const struct gpio_chip msm_gpio_template = {
 	.direction_input  = msm_gpio_direction_input,
 	.direction_output = msm_gpio_direction_output,
 	.get_direction    = msm_gpio_get_direction,
 	.get              = msm_gpio_get,
 	.set              = msm_gpio_set,
-	.request          = gpiochip_generic_request,
+	.request          = msm_gpio_request,
 	.free             = gpiochip_generic_free,
 	.dbg_show         = msm_gpio_dbg_show,
 };
@@ -808,11 +834,57 @@ static void msm_gpio_irq_handler(struct irq_desc *desc)
 	chained_irq_exit(chip, desc);
 }
 
+/**
+ * msm_gpio_get_next_range() - find next range of consecutive gpios
+ * @pctrl: msm_pinctrl object
+ * @pstart: pointer to index of next starting position
+ *
+ * In a sparse GPIO map, available GPIOs are typically collected into blocks.
+ * Given a starting index into the groups[] array, this function will scan all
+ * the gpios until it finds the next block of available GPIOs.
+ *
+ * If groups[*pstart] already points to an available GPIO, then assume that
+ * it is the start of a block.
+ *
+ * The caller is responsible for moving *pstart to after the end of the
+ * previous block so that it this function can find the next block.
+ *
+ * Return: The count of the block starting at @pstart, or 0 if there are no
+ *         more blocks.
+ */
+static unsigned int msm_gpio_get_next_range(struct msm_pinctrl *pctrl,
+					    unsigned int *pstart)
+{
+	const struct msm_pingroup *groups = pctrl->soc->groups;
+	unsigned int ngpio = pctrl->soc->ngpios;
+	unsigned int count = 0;
+	unsigned int start = *pstart;
+
+	/* Find the first available GPIO */
+	while (!groups[start].npins)
+		if (++start == ngpio)
+			/* None found, so just exit */
+			return 0;
+
+	*pstart = start;
+
+	/* Count the number of those GPIOs in a row */
+	while (groups[start].npins) {
+		count++;
+		if (++start == ngpio)
+			break;
+	}
+
+	return count;
+}
+
 static int msm_gpio_init(struct msm_pinctrl *pctrl)
 {
 	struct gpio_chip *chip;
 	int ret;
 	unsigned ngpio = pctrl->soc->ngpios;
+	const struct msm_pingroup *groups = pctrl->soc->groups;
+	unsigned int i, start = 0, count;
 
 	if (WARN_ON(ngpio > MAX_NR_GPIO))
 		return -EINVAL;
@@ -825,13 +897,39 @@ static int msm_gpio_init(struct msm_pinctrl *pctrl)
 	chip->owner = THIS_MODULE;
 	chip->of_node = pctrl->dev->of_node;
 
+	/* If the GPIO map is sparse, then we need to disable specific IRQs */
+	chip->irq_need_valid_mask = pctrl->soc->sparse;
+
 	ret = gpiochip_add_data(&pctrl->chip, pctrl);
 	if (ret) {
 		dev_err(pctrl->dev, "Failed register gpiochip\n");
 		return ret;
 	}
 
-	ret = gpiochip_add_pin_range(&pctrl->chip, dev_name(pctrl->dev), 0, 0, chip->ngpio);
+	/*
+	 * If irq_need_valid_mask is true, then gpiochip_add_data() will
+	 * initialize irq_valid_mask to all 1s.  We need to clear all the
+	 * GPIOs that are unavailable, and we need to find each block
+	 * of consecutive available GPIOs are add them as pin ranges.
+	 */
+	if (chip->irq_need_valid_mask) {
+		for (i = 0; i < ngpio; i++)
+			if (!groups[i].npins)
+				clear_bit(i, pctrl->chip.irq_valid_mask);
+
+		while ((count = msm_gpio_get_next_range(pctrl, &start))) {
+			ret = gpiochip_add_pin_range(&pctrl->chip,
+						     dev_name(pctrl->dev),
+						     start, start, count);
+			if (ret)
+				break;
+			start += count;
+		}
+	} else {
+		ret = gpiochip_add_pin_range(&pctrl->chip, dev_name(pctrl->dev),
+					     0, 0, ngpio);
+	}
+
 	if (ret) {
 		dev_err(pctrl->dev, "Failed to add pin range\n");
 		gpiochip_remove(&pctrl->chip);
diff --git a/drivers/pinctrl/qcom/pinctrl-msm.h b/drivers/pinctrl/qcom/pinctrl-msm.h
index 9b9feea540ff..70762bcb84cb 100644
--- a/drivers/pinctrl/qcom/pinctrl-msm.h
+++ b/drivers/pinctrl/qcom/pinctrl-msm.h
@@ -107,6 +107,7 @@ struct msm_pingroup {
  * @ngroups:	    The numbmer of entries in @groups.
  * @ngpio:	    The number of pingroups the driver should expose as GPIOs.
  * @pull_no_keeper: The SoC does not support keeper bias.
+ * @sparse:         The GPIO map is sparse (some GPIOs have npins == 0)
  */
 struct msm_pinctrl_soc_data {
 	const struct pinctrl_pin_desc *pins;
@@ -117,6 +118,7 @@ struct msm_pinctrl_soc_data {
 	unsigned ngroups;
 	unsigned ngpios;
 	bool pull_no_keeper;
+	bool sparse;
 };
 
 int msm_pinctrl_probe(struct platform_device *pdev,
-- 
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