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/pinctrl/qcom/pinctrl-spmi-gpio.c b/drivers/pinctrl/qcom/pinctrl-spmi-gpio.c
index fd5fff9adff0..3be2a08ae3a6 100644
--- a/drivers/pinctrl/qcom/pinctrl-spmi-gpio.c
+++ b/drivers/pinctrl/qcom/pinctrl-spmi-gpio.c
@@ -966,16 +966,13 @@ static int pmic_gpio_child_to_parent_hwirq(struct gpio_chip *chip,
 	return 0;
 }
 
-static void *pmic_gpio_populate_parent_fwspec(struct gpio_chip *chip,
-					     unsigned int parent_hwirq,
-					     unsigned int parent_type)
+static int pmic_gpio_populate_parent_fwspec(struct gpio_chip *chip,
+					    union gpio_irq_fwspec *gfwspec,
+					    unsigned int parent_hwirq,
+					    unsigned int parent_type)
 {
 	struct pmic_gpio_state *state = gpiochip_get_data(chip);
-	struct irq_fwspec *fwspec;
-
-	fwspec = kzalloc(sizeof(*fwspec), GFP_KERNEL);
-	if (!fwspec)
-		return NULL;
+	struct irq_fwspec *fwspec = &gfwspec->fwspec;
 
 	fwspec->fwnode = chip->irq.parent_domain->fwnode;
 
@@ -985,7 +982,7 @@ static void *pmic_gpio_populate_parent_fwspec(struct gpio_chip *chip,
 	/* param[2] must be left as 0 */
 	fwspec->param[3] = parent_type;
 
-	return fwspec;
+	return 0;
 }
 
 static int pmic_gpio_probe(struct platform_device *pdev)