[PATCH] pinctrl: amd: Steer GPIO interrupt to low power/efficiency cores

[PATCH] pinctrl: amd: Steer GPIO interrupt to low power/efficiency cores

[Mario Limonciello]

On hybrid x86 systems the GPIO controller interrupt can be a frequent
wake and handler source.  Servicing it on a performance core can wake that
core unnecessarily.

Prefer routing it to low power cores, then to efficiency (dense) cores,
using the CPU type from the x86 topology information.  If the system has
neither core type (non-hybrid), leave the affinity untouched.

The placement is applied with irq_set_affinity(), so userspace is still
free to override it.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/pinctrl/pinctrl-amd.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/drivers/pinctrl/pinctrl-amd.c b/drivers/pinctrl/pinctrl-amd.c
index 30da75bb93b9a..3ae199cc93435 100644
--- a/drivers/pinctrl/pinctrl-amd.c
+++ b/drivers/pinctrl/pinctrl-amd.c
@@ -31,6 +31,8 @@
 #include <linux/pinctrl/pinmux.h>
 #include <linux/string_choices.h>
 #include <linux/suspend.h>
+#include <linux/cpumask.h>
+#include <linux/processor.h>
 
 #include "core.h"
 #include "pinctrl-utils.h"
@@ -1272,6 +1274,41 @@ static void __iomem *amd_get_named_res(struct device *dev, struct platform_devic
 	return base;
 }
 
+#ifdef CONFIG_X86_64
+/*
+ * On hybrid systems prefer to service the GPIO interrupt on low power cores,
+ * then on efficiency (dense) cores to save power.  Userspace can still
+ * override the placement.  Do nothing if neither core type exists.
+ */
+static void amd_gpio_set_irq_affinity(struct amd_gpio *gpio_dev)
+{
+	static const enum x86_topology_cpu_type types[] = {
+		TOPO_CPU_TYPE_LOW_POWER,
+		TOPO_CPU_TYPE_EFFICIENCY,
+	};
+	cpumask_var_t mask;
+	int cpu, i;
+
+	if (!zalloc_cpumask_var(&mask, GFP_KERNEL))
+		return;
+
+	for (i = 0; i < ARRAY_SIZE(types); i++) {
+		for_each_possible_cpu(cpu) {
+			if (cpu_data(cpu).topo.cpu_type == types[i])
+				cpumask_set_cpu(cpu, mask);
+		}
+		if (!cpumask_empty(mask)) {
+			irq_set_affinity(gpio_dev->irq, mask);
+			break;
+		}
+	}
+
+	free_cpumask_var(mask);
+}
+#else
+static void amd_gpio_set_irq_affinity(struct amd_gpio *gpio_dev) {}
+#endif
+
 static int amd_gpio_probe(struct platform_device *pdev)
 {
 	int ret = 0;
@@ -1377,6 +1414,8 @@ static int amd_gpio_probe(struct platform_device *pdev)
 	if (ret)
 		goto out2;
 
+	amd_gpio_set_irq_affinity(gpio_dev);
+
 	platform_set_drvdata(pdev, gpio_dev);
 	acpi_register_wakeup_handler(gpio_dev->irq, amd_gpio_check_wake, gpio_dev);
 	amd_gpio_register_s2idle_ops();

---
base-commit: 7475ea8b58616b33c04afb976cf0fbaad9dd63fb
change-id: 20261111-superm1-pinctrl-power-improvement-93440daeb293

Best regards,
--  
Mario Limonciello <mario.limonciello@amd.com>

Re: [PATCH] pinctrl: amd: Steer GPIO interrupt to low power/efficiency cores

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential
issues to consider:
- [Low] pinctrl: amd: offline low-power CPUs prevent fallback in
  amd_gpio_set_irq_affinity()
- [Low] pinctrl: amd: UML build failure in amd_gpio_set_irq_affinity()
  under CONFIG_X86_64
--

commit 9979566a45b6fdd26d48ee240bec752ee33586ba
Author: Mario Limonciello <mario.limonciello@amd.com>

pinctrl: amd: Steer GPIO interrupt to low power/efficiency cores

This commit steers the AMD GPIO controller interrupt to low power or
efficiency cores on hybrid x86 systems during probe using
irq_set_affinity().

> diff --git a/drivers/pinctrl/pinctrl-amd.c b/drivers/pinctrl/pinctrl-amd.c
> index 30da75bb93b9a..3ae199cc93435 100644
> --- a/drivers/pinctrl/pinctrl-amd.c
> +++ b/drivers/pinctrl/pinctrl-amd.c
[ ... ]
> @@ -1272,6 +1274,41 @@ static void __iomem *amd_get_named_res(struct device *dev, struct platform_devic
>  	return base;
>  }
>  
> +#ifdef CONFIG_X86_64
> +/*
> + * On hybrid systems prefer to service the GPIO interrupt on low power cores,
> + * then on efficiency (dense) cores to save power.  Userspace can still
> + * override the placement.  Do nothing if neither core type exists.
> + */
> +static void amd_gpio_set_irq_affinity(struct amd_gpio *gpio_dev)
> +{
> +	static const enum x86_topology_cpu_type types[] = {
> +		TOPO_CPU_TYPE_LOW_POWER,
> +		TOPO_CPU_TYPE_EFFICIENCY,
> +	};

[Severity: Low]
Does guarding amd_gpio_set_irq_affinity() with CONFIG_X86_64 break 64-bit
ARCH=um builds when CONFIG_COMPILE_TEST is enabled?

On 64-bit User Mode Linux, arch/x86/um/Kconfig defines CONFIG_X86_64=y
without CONFIG_X86, and the UML processor headers define struct cpuinfo_um
rather than enum x86_topology_cpu_type or per-CPU cpu_data(cpu).  Guarding
this with CONFIG_X86 (or excluding CONFIG_UML) would avoid the build
failure.

> +	cpumask_var_t mask;
> +	int cpu, i;
> +
> +	if (!zalloc_cpumask_var(&mask, GFP_KERNEL))
> +		return;
> +
> +	for (i = 0; i < ARRAY_SIZE(types); i++) {
> +		for_each_possible_cpu(cpu) {
> +			if (cpu_data(cpu).topo.cpu_type == types[i])
> +				cpumask_set_cpu(cpu, mask);
> +		}
> +		if (!cpumask_empty(mask)) {
> +			irq_set_affinity(gpio_dev->irq, mask);
> +			break;
> +		}
> +	}

[Severity: Low]
Can offline low-power CPUs prevent amd_gpio_set_irq_affinity() from falling
back to efficiency cores?

When a CPU is offlined via hotplug on x86, remove_siblinginfo() leaves
cpu_data(cpu).topo.cpu_type intact.  Because the loop iterates over
for_each_possible_cpu(cpu) and breaks unconditionally whenever mask is
non-empty, if all TOPO_CPU_TYPE_LOW_POWER CPUs are offline when
amd_gpio_probe() runs, irq_do_set_affinity() rejects the offline-only mask
with -EINVAL and TOPO_CPU_TYPE_EFFICIENCY is never tried.  Iterating over
for_each_online_cpu(cpu) (or checking the return value of
irq_set_affinity()) would allow the fallback to proceed.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261111-superm1-pinctrl-power-improvement-v1-1-4bbe6cdbd2e8@amd.com?part=1

Re: [PATCH] pinctrl: amd: Steer GPIO interrupt to low power/efficiency cores

[kernel test robot]

Hi Mario,

kernel test robot noticed the following build errors:

[auto build test ERROR on 7475ea8b58616b33c04afb976cf0fbaad9dd63fb]

url:    https://github.com/intel-lab-lkp/linux/commits/Mario-Limonciello/pinctrl-amd-Steer-GPIO-interrupt-to-low-power-efficiency-cores/20261111-100708
base:   7475ea8b58616b33c04afb976cf0fbaad9dd63fb
patch link:    https://lore.kernel.org/r/20261111-superm1-pinctrl-power-improvement-v1-1-4bbe6cdbd2e8%40amd.com
patch subject: [PATCH] pinctrl: amd: Steer GPIO interrupt to low power/efficiency cores
config: um-randconfig-1000-20261112 (https://download.01.org/0day-ci/archive/20261112/202611120840.VN9Z8N3s-lkp@intel.com/config)
compiler: clang version 18.1.8 (https://github.com/llvm/llvm-project 3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20261112/202611120840.VN9Z8N3s-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202611120840.VN9Z8N3s-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from drivers/pinctrl/pinctrl-amd.c:20:
   In file included from include/linux/io.h:12:
   In file included from arch/um/include/asm/io.h:24:
   include/asm-generic/io.h:1209:55: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
    1209 |         return (port > MMIO_UPPER_LIMIT) ? NULL : PCI_IOBASE + port;
         |                                                   ~~~~~~~~~~ ^
>> drivers/pinctrl/pinctrl-amd.c:1285:47: error: array has incomplete element type 'const enum x86_topology_cpu_type'
    1285 |         static const enum x86_topology_cpu_type types[] = {
         |                                                      ^
   drivers/pinctrl/pinctrl-amd.c:1285:20: note: forward declaration of 'enum x86_topology_cpu_type'
    1285 |         static const enum x86_topology_cpu_type types[] = {
         |                           ^
>> drivers/pinctrl/pinctrl-amd.c:1286:3: error: use of undeclared identifier 'TOPO_CPU_TYPE_LOW_POWER'
    1286 |                 TOPO_CPU_TYPE_LOW_POWER,
         |                 ^
>> drivers/pinctrl/pinctrl-amd.c:1287:3: error: use of undeclared identifier 'TOPO_CPU_TYPE_EFFICIENCY'
    1287 |                 TOPO_CPU_TYPE_EFFICIENCY,
         |                 ^
>> drivers/pinctrl/pinctrl-amd.c:1297:8: error: call to undeclared function 'cpu_data'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
    1297 |                         if (cpu_data(cpu).topo.cpu_type == types[i])
         |                             ^
>> drivers/pinctrl/pinctrl-amd.c:1297:21: error: member reference base type 'int' is not a structure or union
    1297 |                         if (cpu_data(cpu).topo.cpu_type == types[i])
         |                             ~~~~~~~~~~~~~^~~~~
   1 warning and 5 errors generated.


vim +1285 drivers/pinctrl/pinctrl-amd.c

  1276	
  1277	#ifdef CONFIG_X86_64
  1278	/*
  1279	 * On hybrid systems prefer to service the GPIO interrupt on low power cores,
  1280	 * then on efficiency (dense) cores to save power.  Userspace can still
  1281	 * override the placement.  Do nothing if neither core type exists.
  1282	 */
  1283	static void amd_gpio_set_irq_affinity(struct amd_gpio *gpio_dev)
  1284	{
> 1285		static const enum x86_topology_cpu_type types[] = {
> 1286			TOPO_CPU_TYPE_LOW_POWER,
> 1287			TOPO_CPU_TYPE_EFFICIENCY,
  1288		};
  1289		cpumask_var_t mask;
  1290		int cpu, i;
  1291	
  1292		if (!zalloc_cpumask_var(&mask, GFP_KERNEL))
  1293			return;
  1294	
  1295		for (i = 0; i < ARRAY_SIZE(types); i++) {
  1296			for_each_possible_cpu(cpu) {
> 1297				if (cpu_data(cpu).topo.cpu_type == types[i])
  1298					cpumask_set_cpu(cpu, mask);
  1299			}
  1300			if (!cpumask_empty(mask)) {
  1301				irq_set_affinity(gpio_dev->irq, mask);
  1302				break;
  1303			}
  1304		}
  1305	
  1306		free_cpumask_var(mask);
  1307	}
  1308	#else
  1309	static void amd_gpio_set_irq_affinity(struct amd_gpio *gpio_dev) {}
  1310	#endif
  1311	

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki