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

1 files changed, 18 insertions, 24 deletions

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);