[PATCH v2 04/12] platform/apple-gmux: Fix Interrupts for MMIO systems

[Atharva Tiwari <atharvatiwarilinuxdev@gmail.com>]

on MMIO systems, we need check to for failure in interrupts,
and we have implimented display hotplug to wake up the gpu.

Tested-by: Sebastian Zygadlo <szgit@icloud.com>
Tested-by: Yossef Osman <yossef.osman@proton.me>
Co-developed-by: Andre Eikmeyer <dev@deq.rocks>
Signed-off-by: Andre Eikmeyer <dev@deq.rocks>
Signed-off-by: Atharva Tiwari <atharvatiwarilinuxdev@gmail.com>
---
 drivers/platform/x86/apple-gmux.c | 101 ++++++++++++++++++++++++++----
 1 file changed, 88 insertions(+), 13 deletions(-)

diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c
index 9625551e5..37ba20779 100644
--- a/drivers/platform/x86/apple-gmux.c
+++ b/drivers/platform/x86/apple-gmux.c
@@ -6,6 +6,8 @@
  *  Copyright (C) 2010-2012 Andreas Heider <andreas@meetr.de>
  *  Copyright (C) 2015 Lukas Wunner <lukas@wunner.de>
  *  Copyright (C) 2023 Orlando Chamberlain <orlandoch.dev@gmail.com>
+ *  Copyright (C) 2026 Atharva Tiwari <atharvatiwarilinuxdev@gmail.com>
+ *  Copyright (C) 2026 Andre Eikmeyer <dev@deq.rocks>
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
@@ -22,6 +24,8 @@
 #include <linux/pci.h>
 #include <linux/vga_switcheroo.h>
 #include <linux/debugfs.h>
+#include <linux/workqueue.h>
+#include <linux/pm_runtime.h>
 #include <acpi/video.h>
 #include <asm/io.h>
 
@@ -65,6 +69,10 @@ struct apple_gmux_data {
 
 	struct backlight_device *bdev;
 
+	/* interrupt handling data */
+	u8 external_state;
+	struct work_struct interrupt_work;
+
 	/* power handling data */
 	struct pci_dev *discrete_pdev;
 	enum apple_gmux_type type;
@@ -103,6 +111,7 @@ struct apple_gmux_config {
 
 #define GMUX_INTERRUPT_STATUS_ACTIVE	0
 #define GMUX_INTERRUPT_STATUS_DISPLAY	(1 << 0)
+#define GMUX_INTERRUPT_STATUS_FAILED	(1 << 1)
 #define GMUX_INTERRUPT_STATUS_POWER	(1 << 2)
 #define GMUX_INTERRUPT_STATUS_HOTPLUG	(1 << 3)
 
@@ -412,8 +421,8 @@ static const struct backlight_ops gmux_bl_ops = {
  * the discrete GPU can then be woken to drive the newly connected display.
  * The ability to switch AUX on these generations could be used to improve
  * reliability of hotplug detection by having the integrated GPU poll the
- * ports while the discrete GPU is asleep, but currently we do not make use
- * of this feature.
+ * ports while the discrete GPU is asleep, but currently we only make use of
+ * this feature on MMIO/T2 Macs.
  *
  * Our switching policy for the external port is that on those generations
  * which are able to switch it fully, the port is switched together with the
@@ -777,9 +786,10 @@ static const struct apple_gmux_config apple_gmux_mmio = {
  * value is read and then inverted.
  *
  * Because Linux masquerades as Darwin, it ends up in the notification-only code
- * path. On MMIO gmux's, this seems to lead to us being unable to clear interrupts,
- * unless we call GMSP(0). Without this, there is a flood of status=0 interrupts
- * that can't be cleared. This issue seems to be unique to MMIO gmux's.
+ * path. On MMIO gmux's, The Polarity is initally left in a undefined state leading
+ * to lots of interrupts, that we can't clear, to fix this we set the polarity to 0
+ * everytime we enable interrupts, On MMIO gmux's, GMLV reads the same GPIO pin as
+ * GMSP, and setting the polarity to 1, stops the Interrupts completely.
  */
 
 static inline void gmux_disable_interrupts(struct apple_gmux_data *gmux_data)
@@ -788,8 +798,11 @@ static inline void gmux_disable_interrupts(struct apple_gmux_data *gmux_data)
 		    GMUX_INTERRUPT_DISABLE);
 }
 
-static inline void gmux_enable_interrupts(struct apple_gmux_data *gmux_data)
+static inline void gmux_enable_interrupts(struct apple_gmux_data *gmux_data, bool do_gmsp)
 {
+	if (gmux_data->type == APPLE_GMUX_TYPE_MMIO && do_gmsp)
+		acpi_execute_simple_method(gmux_data->dhandle, "GMSP", 0);
+
 	gmux_write8(gmux_data, GMUX_PORT_INTERRUPT_ENABLE,
 		    GMUX_INTERRUPT_ENABLE);
 }
@@ -806,23 +819,78 @@ static void gmux_clear_interrupts(struct apple_gmux_data *gmux_data)
 	/* to clear interrupts write back current status */
 	status = gmux_interrupt_get_status(gmux_data);
 	gmux_write8(gmux_data, GMUX_PORT_INTERRUPT_STATUS, status);
-	/* Prevent flood of status=0 interrupts */
-	if (gmux_data->config == &apple_gmux_mmio)
-		acpi_execute_simple_method(gmux_data->dhandle, "GMSP", 0);
 }
 
+static void gmux_notify_work(struct work_struct *work)
+{
+	struct apple_gmux_data *gmux_data =
+		container_of(work, struct apple_gmux_data, interrupt_work);
+	u8 status;
+	bool turn_on_gpu = false;
+
+	status = gmux_interrupt_get_status(gmux_data);
+	if (!status)
+		return;
+
+	gmux_disable_interrupts(gmux_data);
+	pr_debug("Notify handler called: status %d\n", status);
+	acpi_execute_simple_method(gmux_data->dhandle, "GMSP", 0);
+
+	status = gmux_interrupt_get_status(gmux_data);
+	while (status) {
+		gmux_write8(gmux_data, GMUX_PORT_INTERRUPT_STATUS, status);
+		if (status & GMUX_INTERRUPT_STATUS_FAILED) {
+			pr_warn_ratelimited("interrupt failed: status: 0x%x\n", status);
+			status = gmux_interrupt_get_status(gmux_data);
+			continue;
+		}
+		if (status & GMUX_INTERRUPT_STATUS_POWER)
+			complete(&gmux_data->powerchange_done);
+
+		if (status & GMUX_INTERRUPT_STATUS_HOTPLUG) {
+			/*
+			 * We get an interrupt every time a display connects or disconnects, but
+			 * the GET_DISPLAY port only tells us if a display is connected or not,
+			 * so we resume every time a display is connected or disconnected.
+			 */
+			u8 external_state = gmux_read8(gmux_data,
+						GMUX_PORT_SWITCH_GET_DISPLAY);
+			if (external_state != gmux_data->external_state) {
+				gmux_data->external_state = external_state;
+				if (external_state)
+					pr_debug("A display has been connected\n");
+				else
+					pr_debug("All displays has been disconnected\n");
+			}
+			turn_on_gpu = true;
+		}
+		status = gmux_interrupt_get_status(gmux_data);
+	}
+
+	gmux_enable_interrupts(gmux_data, 0);
+
+	if (turn_on_gpu && !gmux_data->external_switchable && gmux_data->discrete_pdev &&
+			    pm_runtime_enabled(&gmux_data->discrete_pdev->dev))
+		pm_request_resume(&gmux_data->discrete_pdev->dev);
+
+}
 static void gmux_notify_handler(acpi_handle device, u32 value, void *context)
 {
 	u8 status;
 	struct pnp_dev *pnp = (struct pnp_dev *)context;
 	struct apple_gmux_data *gmux_data = pnp_get_drvdata(pnp);
 
+	if (gmux_data->type == APPLE_GMUX_TYPE_MMIO) {
+		schedule_work(&gmux_data->interrupt_work);
+		return;
+	}
+
 	status = gmux_interrupt_get_status(gmux_data);
 	gmux_disable_interrupts(gmux_data);
 	pr_debug("Notify handler called: status %d\n", status);
 
 	gmux_clear_interrupts(gmux_data);
-	gmux_enable_interrupts(gmux_data);
+	gmux_enable_interrupts(gmux_data, 0);
 
 	if (status & GMUX_INTERRUPT_STATUS_POWER)
 		complete(&gmux_data->powerchange_done);
@@ -916,7 +984,7 @@ static int gmux_resume(struct device *dev)
 	struct pnp_dev *pnp = to_pnp_dev(dev);
 	struct apple_gmux_data *gmux_data = pnp_get_drvdata(pnp);
 
-	gmux_enable_interrupts(gmux_data);
+	gmux_enable_interrupts(gmux_data, 1);
 	gmux_write_switch_state(gmux_data);
 	if (gmux_data->power_state == VGA_SWITCHEROO_OFF)
 		gmux_set_discrete_state(gmux_data, gmux_data->power_state);
@@ -1072,6 +1140,8 @@ static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
 			goto err_notify;
 		}
 
+		if (type == APPLE_GMUX_TYPE_MMIO)
+			INIT_WORK(&gmux_data->interrupt_work, gmux_notify_work);
 		status = acpi_enable_gpe(NULL, gmux_data->gpe);
 		if (ACPI_FAILURE(status)) {
 			pr_err("Cannot enable gpe: %s\n",
@@ -1094,7 +1164,7 @@ static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
 
 	apple_gmux_data = gmux_data;
 	init_completion(&gmux_data->powerchange_done);
-	gmux_enable_interrupts(gmux_data);
+	gmux_enable_interrupts(gmux_data, 1);
 	gmux_read_switch_state(gmux_data);
 
 	/*
@@ -1124,6 +1194,9 @@ static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
 		acpi_remove_notify_handler(gmux_data->dhandle,
 					   ACPI_DEVICE_NOTIFY,
 					   &gmux_notify_handler);
+
+	if (gmux_data->type == APPLE_GMUX_TYPE_MMIO)
+		cancel_work_sync(&gmux_data->interrupt_work);
 err_notify:
 	backlight_device_unregister(bdev);
 err_unmap:
@@ -1145,7 +1218,6 @@ static void gmux_remove(struct pnp_dev *pnp)
 
 	gmux_fini_debugfs(gmux_data);
 	vga_switcheroo_unregister_handler();
-	pci_dev_put(gmux_data->discrete_pdev);
 	gmux_disable_interrupts(gmux_data);
 	if (gmux_data->gpe >= 0) {
 		acpi_disable_gpe(NULL, gmux_data->gpe);
@@ -1154,6 +1226,9 @@ static void gmux_remove(struct pnp_dev *pnp)
 					   &gmux_notify_handler);
 	}
 
+	if (gmux_data->type == APPLE_GMUX_TYPE_MMIO)
+		cancel_work_sync(&gmux_data->interrupt_work);
+	pci_dev_put(gmux_data->discrete_pdev);
 	backlight_device_unregister(gmux_data->bdev);
 
 	if (gmux_data->iomem_base) {
-- 
2.55.0