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[RFC/RFT PATCH 0/3] gpiolib: make gpio irqchip compatible with sparse_irq

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  [RFC/RFT PATCH 0/3] gpiolib: make gpio irqchip compatible with sparse_irq Grygorii Strashko <grygorii.strashko@ti.com> - 2017-07-09 00:50 +0200
    [RFC/RFT PATCH 2/3] gpio: pxa: remove gpio_to_irq() from hw irq handlers Grygorii Strashko <grygorii.strashko@ti.com> - 2017-07-09 00:50 +0200

#1683666 — [RFC/RFT PATCH 0/3] gpiolib: make gpio irqchip compatible with sparse_irq

The idea of this changes was inspired by discussion [1].

Now IRQ mappings are always created for all (allowed) GPIOs in GPIO irqchip in
gpiochip_irqchip_add_key() and this goes against the idea of SPARSE_IRQ and,
as result, leads to:
 - increasing of memory consumption because of allocated IRQ descriptors most
of which will never ever be used (especially on platform with a
high number of GPIOs).
 - imposibility to use GPIO irqchip APIs by gpio drivers when HW implements
GPIO IRQ functionality as IRQ crossbar/multiplexer which has only limited
number of IRQ outputs (example from [1], all GPIOs can be mapped on only 8
IRQs).

Hence, remove static IRQ mapping code from gpiochip_irqchip_add_key() and
instead replace irq_find_mapping() with irq_create_mapping() in
gpiochip_to_irq(). Also add additional gpiochip_irqchip_irq_valid() calls
in gpiochip_to_irq() and gpiochip_irq_map().

After this change gpio2irq mapping will happen the following way when GPIO
irqchip APIs are used by gpio driver:
 - IRQ mappings will be created statically if driver passes first_irq>0
vlaue in gpiochip_irqchip_add_key().
 - IRQ mappings will be created dynamically from gpio_to_irq() or
of_irq_get().

Tested on am335x-evm and dra72-evm-revc.
- dra72-evm-revc: number of created irq mappings decreased from 402 -> 135
- am335x-evm: number of created irq mappings decreased from 188 -> 63

It's good to have more testing feedbacks for these patches 
(personally I do not expect regressions, but who knows). One possible side 
effect is "Cannot allocate irq_descs @ IRQ%d, assuming pre-allocated\n" message
during boot, but in this case it might be good to take a look on such GPIO
drivers to understand why they need to allocate IRQ descriptors.

[1] https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1435847.html

Grygorii Strashko (3):
  gpio: tegra: remove gpio_to_irq() from hw irq handlers
  gpio: pxa: remove gpio_to_irq() from hw irq handlers
  gpiolib: make gpio irqchip compatible with sparse_irq

 drivers/gpio/gpio-pxa.c     |  8 +++++---
 drivers/gpio/gpio-tegra.c   |  3 ++-
 drivers/gpio/gpiolib.c      | 29 ++++++-----------------------
 include/linux/gpio/driver.h |  1 -
 4 files changed, 13 insertions(+), 28 deletions(-)

-- 
2.10.1

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#1683667 — [RFC/RFT PATCH 2/3] gpio: pxa: remove gpio_to_irq() from hw irq handlers

gpio_to_irq() API expected to be used by GPIO consumers and
not drivers and there are no guarantee that its gpiolib implementation
is irq safe.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
---
 drivers/gpio/gpio-pxa.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpio/gpio-pxa.c b/drivers/gpio/gpio-pxa.c
index 832f3e4..6029899 100644
--- a/drivers/gpio/gpio-pxa.c
+++ b/drivers/gpio/gpio-pxa.c
@@ -451,7 +451,9 @@ static irqreturn_t pxa_gpio_demux_handler(int in_irq, void *d)
 			for_each_set_bit(n, &gedr, BITS_PER_LONG) {
 				loop = 1;
 
-				generic_handle_irq(gpio_to_irq(gpio + n));
+				generic_handle_irq(
+					irq_find_mapping(pchip->irqdomain,
+							 gpio + n));
 			}
 		}
 		handled += loop;
@@ -465,9 +467,9 @@ static irqreturn_t pxa_gpio_direct_handler(int in_irq, void *d)
 	struct pxa_gpio_chip *pchip = d;
 
 	if (in_irq == pchip->irq0) {
-		generic_handle_irq(gpio_to_irq(0));
+		generic_handle_irq(irq_find_mapping(pchip->irqdomain, 0));
 	} else if (in_irq == pchip->irq1) {
-		generic_handle_irq(gpio_to_irq(1));
+		generic_handle_irq(irq_find_mapping(pchip->irqdomain, 1));
 	} else {
 		pr_err("%s() unknown irq %d\n", __func__, in_irq);
 		return IRQ_NONE;
-- 
2.10.1

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