gpio: Remove dynamic allocation from populate_parent_alloc_arg()

The gpiolib is unique in the way it uses intermediate fwspecs
when feeding an interrupt specifier to the parent domain, as it
relies on the populate_parent_alloc_arg() callback to perform
a dynamic allocation.

This is pretty inefficient (we free the structure almost immediately),
and the only reason this isn't a stack allocation is that our
ThunderX friend uses MSIs rather than a FW-constructed structure.

Let's solve it by providing a new type composed of the union
of a struct irq_fwspec and a msi_info_t, which satisfies both
requirements. This allows us to use a stack allocation, and we
can move the handful of users to this new scheme.

Also perform some additional cleanup, such as getting rid of the
stub versions of the irq_domain_translate_*cell helpers, which
are never used when CONFIG_IRQ_DOMAIN_HIERARCHY isn't selected.

Tested on a Tegra186.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: Daniel Palmer <daniel@thingy.jp>
Cc: Romain Perier <romain.perier@gmail.com>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Jonathan Hunter <jonathanh@nvidia.com>
Cc: Robert Richter <rric@kernel.org>
Cc: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
Cc: Andy Gross <agross@kernel.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: Bartosz Golaszewski <brgl@bgdev.pl>
Link: https://lore.kernel.org/r/20220707182314.66610-2-prabhakar.mahadev-lad.rj@bp.renesas.com

6 files changed, 48 insertions, 69 deletions

diff --git a/drivers/gpio/gpio-msc313.c b/drivers/gpio/gpio-msc313.c
index b2c90bdd39d0..52d7b8d99170 100644
--- a/drivers/gpio/gpio-msc313.c
+++ b/drivers/gpio/gpio-msc313.c
@@ -550,15 +550,12 @@ static struct irq_chip msc313_gpio_irqchip = {
  * so we need to provide the fwspec. Essentially gpiochip_populate_parent_fwspec_twocell
  * that puts GIC_SPI into the first cell.
  */
-static void *msc313_gpio_populate_parent_fwspec(struct gpio_chip *gc,
-					     unsigned int parent_hwirq,
-					     unsigned int parent_type)
+static int msc313_gpio_populate_parent_fwspec(struct gpio_chip *gc,
+					      union gpio_irq_fwspec *gfwspec,
+					      unsigned int parent_hwirq,
+					      unsigned int parent_type)
 {
-	struct irq_fwspec *fwspec;
-
-	fwspec = kmalloc(sizeof(*fwspec), GFP_KERNEL);
-	if (!fwspec)
-		return NULL;
+	struct irq_fwspec *fwspec = &gfwspec->fwspec;
 
 	fwspec->fwnode = gc->irq.parent_domain->fwnode;
 	fwspec->param_count = 3;
@@ -566,7 +563,7 @@ static void *msc313_gpio_populate_parent_fwspec(struct gpio_chip *gc,
 	fwspec->param[1] = parent_hwirq;
 	fwspec->param[2] = parent_type;
 
-	return fwspec;
+	return 0;
 }
 
 static int msc313e_gpio_child_to_parent_hwirq(struct gpio_chip *chip,
diff --git a/drivers/gpio/gpio-tegra.c b/drivers/gpio/gpio-tegra.c
index ff2d2a1f9c73..e4fb4cb38a0f 100644
--- a/drivers/gpio/gpio-tegra.c
+++ b/drivers/gpio/gpio-tegra.c
@@ -443,15 +443,12 @@ static int tegra_gpio_child_to_parent_hwirq(struct gpio_chip *chip,
 	return 0;
 }
 
-static void *tegra_gpio_populate_parent_fwspec(struct gpio_chip *chip,
-					       unsigned int parent_hwirq,
-					       unsigned int parent_type)
+static int tegra_gpio_populate_parent_fwspec(struct gpio_chip *chip,
+					     union gpio_irq_fwspec *gfwspec,
+					     unsigned int parent_hwirq,
+					     unsigned int parent_type)
 {
-	struct irq_fwspec *fwspec;
-
-	fwspec = kmalloc(sizeof(*fwspec), GFP_KERNEL);
-	if (!fwspec)
-		return NULL;
+	struct irq_fwspec *fwspec = &gfwspec->fwspec;
 
 	fwspec->fwnode = chip->irq.parent_domain->fwnode;
 	fwspec->param_count = 3;
@@ -459,7 +456,7 @@ static void *tegra_gpio_populate_parent_fwspec(struct gpio_chip *chip,
 	fwspec->param[1] = parent_hwirq;
 	fwspec->param[2] = parent_type;
 
-	return fwspec;
+	return 0;
 }
 
 #ifdef CONFIG_PM_SLEEP
diff --git a/drivers/gpio/gpio-tegra186.c b/drivers/gpio/gpio-tegra186.c
index de28a68daea0..54d9fa7da9c1 100644
--- a/drivers/gpio/gpio-tegra186.c
+++ b/drivers/gpio/gpio-tegra186.c
@@ -621,16 +621,13 @@ static int tegra186_gpio_irq_domain_translate(struct irq_domain *domain,
 	return 0;
 }
 
-static void *tegra186_gpio_populate_parent_fwspec(struct gpio_chip *chip,
-						 unsigned int parent_hwirq,
-						 unsigned int parent_type)
+static int tegra186_gpio_populate_parent_fwspec(struct gpio_chip *chip,
+						union gpio_irq_fwspec *gfwspec,
+						unsigned int parent_hwirq,
+						unsigned int parent_type)
 {
 	struct tegra_gpio *gpio = gpiochip_get_data(chip);
-	struct irq_fwspec *fwspec;
-
-	fwspec = kmalloc(sizeof(*fwspec), GFP_KERNEL);
-	if (!fwspec)
-		return NULL;
+	struct irq_fwspec *fwspec = &gfwspec->fwspec;
 
 	fwspec->fwnode = chip->irq.parent_domain->fwnode;
 	fwspec->param_count = 3;
@@ -638,7 +635,7 @@ static void *tegra186_gpio_populate_parent_fwspec(struct gpio_chip *chip,
 	fwspec->param[1] = parent_hwirq;
 	fwspec->param[2] = parent_type;
 
-	return fwspec;
+	return 0;
 }
 
 static int tegra186_gpio_child_to_parent_hwirq(struct gpio_chip *chip,
diff --git a/drivers/gpio/gpio-thunderx.c b/drivers/gpio/gpio-thunderx.c
index 9f66deab46ea..e1dedbca0c85 100644
--- a/drivers/gpio/gpio-thunderx.c
+++ b/drivers/gpio/gpio-thunderx.c
@@ -408,18 +408,15 @@ static int thunderx_gpio_child_to_parent_hwirq(struct gpio_chip *gc,
 	return 0;
 }
 
-static void *thunderx_gpio_populate_parent_alloc_info(struct gpio_chip *chip,
-						      unsigned int parent_hwirq,
-						      unsigned int parent_type)
+static int thunderx_gpio_populate_parent_alloc_info(struct gpio_chip *chip,
+						    union gpio_irq_fwspec *gfwspec,
+						    unsigned int parent_hwirq,
+						    unsigned int parent_type)
 {
-	msi_alloc_info_t *info;
-
-	info = kmalloc(sizeof(*info), GFP_KERNEL);
-	if (!info)
-		return NULL;
+	msi_alloc_info_t *info = &gfwspec->msiinfo;
 
 	info->hwirq = parent_hwirq;
-	return info;
+	return 0;
 }
 
 static int thunderx_gpio_probe(struct pci_dev *pdev,
diff --git a/drivers/gpio/gpio-visconti.c b/drivers/gpio/gpio-visconti.c
index e6534ea1eaa7..5e108ba9956a 100644
--- a/drivers/gpio/gpio-visconti.c
+++ b/drivers/gpio/gpio-visconti.c
@@ -103,15 +103,12 @@ static int visconti_gpio_child_to_parent_hwirq(struct gpio_chip *gc,
 	return -EINVAL;
 }
 
-static void *visconti_gpio_populate_parent_fwspec(struct gpio_chip *chip,
-						  unsigned int parent_hwirq,
-						  unsigned int parent_type)
+static int visconti_gpio_populate_parent_fwspec(struct gpio_chip *chip,
+						union gpio_irq_fwspec *gfwspec,
+						unsigned int parent_hwirq,
+						unsigned int parent_type)
 {
-	struct irq_fwspec *fwspec;
-
-	fwspec = kmalloc(sizeof(*fwspec), GFP_KERNEL);
-	if (!fwspec)
-		return NULL;
+	struct irq_fwspec *fwspec = &gfwspec->fwspec;
 
 	fwspec->fwnode = chip->irq.parent_domain->fwnode;
 	fwspec->param_count = 3;
@@ -119,7 +116,7 @@ static void *visconti_gpio_populate_parent_fwspec(struct gpio_chip *chip,
 	fwspec->param[1] = parent_hwirq;
 	fwspec->param[2] = parent_type;
 
-	return fwspec;
+	return 0;
 }
 
 static int visconti_gpio_probe(struct platform_device *pdev)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 9535f48e18d1..bfde94243752 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1107,7 +1107,7 @@ static int gpiochip_hierarchy_irq_domain_alloc(struct irq_domain *d,
 	irq_hw_number_t hwirq;
 	unsigned int type = IRQ_TYPE_NONE;
 	struct irq_fwspec *fwspec = data;
-	void *parent_arg;
+	union gpio_irq_fwspec gpio_parent_fwspec = {};
 	unsigned int parent_hwirq;
 	unsigned int parent_type;
 	struct gpio_irq_chip *girq = &gc->irq;
@@ -1147,14 +1147,15 @@ static int gpiochip_hierarchy_irq_domain_alloc(struct irq_domain *d,
 	irq_set_probe(irq);
 
 	/* This parent only handles asserted level IRQs */
-	parent_arg = girq->populate_parent_alloc_arg(gc, parent_hwirq, parent_type);
-	if (!parent_arg)
-		return -ENOMEM;
+	ret = girq->populate_parent_alloc_arg(gc, &gpio_parent_fwspec,
+					      parent_hwirq, parent_type);
+	if (ret)
+		return ret;
 
 	chip_dbg(gc, "alloc_irqs_parent for %d parent hwirq %d\n",
 		  irq, parent_hwirq);
 	irq_set_lockdep_class(irq, gc->irq.lock_key, gc->irq.request_key);
-	ret = irq_domain_alloc_irqs_parent(d, irq, 1, parent_arg);
+	ret = irq_domain_alloc_irqs_parent(d, irq, 1, &gpio_parent_fwspec);
 	/*
 	 * If the parent irqdomain is msi, the interrupts have already
 	 * been allocated, so the EEXIST is good.
@@ -1166,7 +1167,6 @@ static int gpiochip_hierarchy_irq_domain_alloc(struct irq_domain *d,
 			 "failed to allocate parent hwirq %d for hwirq %lu\n",
 			 parent_hwirq, hwirq);
 
-	kfree(parent_arg);
 	return ret;
 }
 
@@ -1230,34 +1230,28 @@ static bool gpiochip_hierarchy_is_hierarchical(struct gpio_chip *gc)
 	return !!gc->irq.parent_domain;
 }
 
-void *gpiochip_populate_parent_fwspec_twocell(struct gpio_chip *gc,
-					     unsigned int parent_hwirq,
-					     unsigned int parent_type)
+int gpiochip_populate_parent_fwspec_twocell(struct gpio_chip *gc,
+					    union gpio_irq_fwspec *gfwspec,
+					    unsigned int parent_hwirq,
+					    unsigned int parent_type)
 {
-	struct irq_fwspec *fwspec;
-
-	fwspec = kmalloc(sizeof(*fwspec), GFP_KERNEL);
-	if (!fwspec)
-		return NULL;
+	struct irq_fwspec *fwspec = &gfwspec->fwspec;
 
 	fwspec->fwnode = gc->irq.parent_domain->fwnode;
 	fwspec->param_count = 2;
 	fwspec->param[0] = parent_hwirq;
 	fwspec->param[1] = parent_type;
 
-	return fwspec;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(gpiochip_populate_parent_fwspec_twocell);
 
-void *gpiochip_populate_parent_fwspec_fourcell(struct gpio_chip *gc,
-					      unsigned int parent_hwirq,
-					      unsigned int parent_type)
+int gpiochip_populate_parent_fwspec_fourcell(struct gpio_chip *gc,
+					     union gpio_irq_fwspec *gfwspec,
+					     unsigned int parent_hwirq,
+					     unsigned int parent_type)
 {
-	struct irq_fwspec *fwspec;
-
-	fwspec = kmalloc(sizeof(*fwspec), GFP_KERNEL);
-	if (!fwspec)
-		return NULL;
+	struct irq_fwspec *fwspec = &gfwspec->fwspec;
 
 	fwspec->fwnode = gc->irq.parent_domain->fwnode;
 	fwspec->param_count = 4;
@@ -1266,7 +1260,7 @@ void *gpiochip_populate_parent_fwspec_fourcell(struct gpio_chip *gc,
 	fwspec->param[2] = 0;
 	fwspec->param[3] = parent_type;
 
-	return fwspec;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(gpiochip_populate_parent_fwspec_fourcell);