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, 19 insertions, 23 deletions

diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index b1e0f1f8ee2e..ad5b92b74ccf 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -12,6 +12,8 @@
 #include <linux/property.h>
 #include <linux/types.h>
 
+#include <asm/msi.h>
+
 struct gpio_desc;
 struct of_phandle_args;
 struct device_node;
@@ -23,6 +25,13 @@ enum gpio_lookup_flags;
 
 struct gpio_chip;
 
+union gpio_irq_fwspec {
+	struct irq_fwspec	fwspec;
+#ifdef CONFIG_GENERIC_MSI_IRQ_DOMAIN
+	msi_alloc_info_t	msiinfo;
+#endif
+};
+
 #define GPIO_LINE_DIRECTION_IN	1
 #define GPIO_LINE_DIRECTION_OUT	0
 
@@ -103,9 +112,10 @@ struct gpio_irq_chip {
 	 * variant named &gpiochip_populate_parent_fwspec_fourcell is also
 	 * available.
 	 */
-	void *(*populate_parent_alloc_arg)(struct gpio_chip *gc,
-				       unsigned int parent_hwirq,
-				       unsigned int parent_type);
+	int (*populate_parent_alloc_arg)(struct gpio_chip *gc,
+					 union gpio_irq_fwspec *fwspec,
+					 unsigned int parent_hwirq,
+					 unsigned int parent_type);
 
 	/**
 	 * @child_offset_to_irq:
@@ -646,28 +656,14 @@ struct bgpio_pdata {
 
 #ifdef CONFIG_IRQ_DOMAIN_HIERARCHY
 
-void *gpiochip_populate_parent_fwspec_twocell(struct gpio_chip *gc,
+int gpiochip_populate_parent_fwspec_twocell(struct gpio_chip *gc,
+					    union gpio_irq_fwspec *gfwspec,
+					    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);
-void *gpiochip_populate_parent_fwspec_fourcell(struct gpio_chip *gc,
-					      unsigned int parent_hwirq,
-					      unsigned int parent_type);
-
-#else
-
-static inline void *gpiochip_populate_parent_fwspec_twocell(struct gpio_chip *gc,
-						    unsigned int parent_hwirq,
-						    unsigned int parent_type)
-{
-	return NULL;
-}
-
-static inline void *gpiochip_populate_parent_fwspec_fourcell(struct gpio_chip *gc,
-						     unsigned int parent_hwirq,
-						     unsigned int parent_type)
-{
-	return NULL;
-}
 
 #endif /* CONFIG_IRQ_DOMAIN_HIERARCHY */