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, 6 insertions, 9 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,