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

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

[Grygorii Strashko]

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-u79uwXL29TY76Z2rM5mHXA@public.gmane.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

[RFC/RFT PATCH 1/3] gpio: tegra: remove gpio_to_irq() from hw irq handlers

[Grygorii Strashko]

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-tegra.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpio-tegra.c b/drivers/gpio/gpio-tegra.c
index 88529d3..31b9a86 100644
--- a/drivers/gpio/gpio-tegra.c
+++ b/drivers/gpio/gpio-tegra.c
@@ -389,7 +389,8 @@ static void tegra_gpio_irq_handler(struct irq_desc *desc)
 				chained_irq_exit(chip, desc);
 			}
 
-			generic_handle_irq(gpio_to_irq(gpio + pin));
+			generic_handle_irq(irq_find_mapping(tgi->irq_domain,
+							    gpio + pin));
 		}
 	}
 
-- 
2.10.1

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

[Grygorii Strashko]

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

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

[Grygorii Strashko]

Now IRQ mappings are always created for all (allowed) GPIOs in gpio irqchip in
gpiochip_irqchip_add_key() which 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().

[1] https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1435847.html
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
---
 drivers/gpio/gpiolib.c      | 29 ++++++-----------------------
 include/linux/gpio/driver.h |  1 -
 2 files changed, 6 insertions(+), 24 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 9568708..ee6ba07 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1605,6 +1605,9 @@ static int gpiochip_irq_map(struct irq_domain *d, unsigned int irq,
 {
 	struct gpio_chip *chip = d->host_data;
 
+	if (!gpiochip_irqchip_irq_valid(chip, hwirq))
+		return -ENXIO;
+
 	irq_set_chip_data(irq, chip);
 	/*
 	 * This lock class tells lockdep that GPIO irqs are in a different
@@ -1671,7 +1674,9 @@ static void gpiochip_irq_relres(struct irq_data *d)
 
 static int gpiochip_to_irq(struct gpio_chip *chip, unsigned offset)
 {
-	return irq_find_mapping(chip->irqdomain, offset);
+	if (!gpiochip_irqchip_irq_valid(chip, offset))
+		return -ENXIO;
+	return irq_create_mapping(chip->irqdomain, offset);
 }
 
 /**
@@ -1747,9 +1752,6 @@ int gpiochip_irqchip_add_key(struct gpio_chip *gpiochip,
 			     struct lock_class_key *lock_key)
 {
 	struct device_node *of_node;
-	bool irq_base_set = false;
-	unsigned int offset;
-	unsigned irq_base = 0;
 
 	if (!gpiochip || !irqchip)
 		return -EINVAL;
@@ -1806,25 +1808,6 @@ int gpiochip_irqchip_add_key(struct gpio_chip *gpiochip,
 		irqchip->irq_release_resources = gpiochip_irq_relres;
 	}
 
-	/*
-	 * Prepare the mapping since the irqchip shall be orthogonal to
-	 * any gpiochip calls. If the first_irq was zero, this is
-	 * necessary to allocate descriptors for all IRQs.
-	 */
-	for (offset = 0; offset < gpiochip->ngpio; offset++) {
-		if (!gpiochip_irqchip_irq_valid(gpiochip, offset))
-			continue;
-		irq_base = irq_create_mapping(gpiochip->irqdomain, offset);
-		if (!irq_base_set) {
-			/*
-			 * Store the base into the gpiochip to be used when
-			 * unmapping the irqs.
-			 */
-			gpiochip->irq_base = irq_base;
-			irq_base_set = true;
-		}
-	}
-
 	acpi_gpiochip_request_interrupts(gpiochip);
 
 	return 0;
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index af20369..a3e2e3e 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -165,7 +165,6 @@ struct gpio_chip {
 	 */
 	struct irq_chip		*irqchip;
 	struct irq_domain	*irqdomain;
-	unsigned int		irq_base;
 	irq_flow_handler_t	irq_handler;
 	unsigned int		irq_default_type;
 	unsigned int		irq_chained_parent;
-- 
2.10.1

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

[Linus Walleij]

On Sun, Jul 9, 2017 at 12:44 AM, Grygorii Strashko
<grygorii.strashko@ti.com> wrote:

> Now IRQ mappings are always created for all (allowed) GPIOs in gpio irqchip in
> gpiochip_irqchip_add_key() which 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().
>
> [1] https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1435847.html
> Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>

This is obviously better and what I should have done from the beginning
had I only been smart enough, so what better to do than to throw this in
now for -next and see what happens :)

Patch applied.

Yours,
Linus Walleij

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

[Linus Walleij]

On Sun, Jul 9, 2017 at 12:44 AM, Grygorii Strashko
<grygorii.strashko-l0cyMroinI0@public.gmane.org> wrote:

> 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-l0cyMroinI0@public.gmane.org>

Patch applied.

This is the right thing to do.

PXA developers: please test.

Yours,
Linus Walleij

Re: [RFC/RFT PATCH 1/3] gpio: tegra: remove gpio_to_irq() from hw irq handlers

[Linus Walleij]

On Sun, Jul 9, 2017 at 12:44 AM, Grygorii Strashko
<grygorii.strashko@ti.com> wrote:

> 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>

Patch applied.

This is obviously the right way to do it.

Tegra people: please test.

Yours,
Linus Walleij

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

[Robert Jarzmik]

Linus Walleij <linus.walleij-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> writes:

> On Sun, Jul 9, 2017 at 12:44 AM, Grygorii Strashko
> <grygorii.strashko-l0cyMroinI0@public.gmane.org> wrote:
>
>> 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-l0cyMroinI0@public.gmane.org>
>
> Patch applied.
>
> This is the right thing to do.
>
> PXA developers: please test.

Hi Linus,

Currently pxa25x and pxa27x are broken because of a .data section misalignment
(issue cross arm architectures), so testing is a bit hard for me right now. I'll
wait to have a working again tree to test, and then report.

Cheers.

--
Robert