drm/apple, PCI: apple: Studio Display brightness through DCP, and a PCIe-C replug fix

drivers/gpu/drm/apple/apple_drv.c

@@ -259,6 +259,16 @@ static void appledrm_connector_cleanup(struct drm_connector *connector)
 	kfree(apple_connector);
 }
 
+static int apple_connector_late_register(struct drm_connector *connector)
+{
+	return apple_connector_backlight_late_register(to_apple_connector(connector));
+}
+
+static void apple_connector_early_unregister(struct drm_connector *connector)
+{
+	apple_connector_backlight_early_unregister(to_apple_connector(connector));
+}
+
 static const struct drm_connector_funcs apple_connector_funcs = {
 	.fill_modes		= drm_helper_probe_single_connector_modes,
 	.destroy		= appledrm_connector_cleanup,
@@ -268,6 +278,8 @@ static const struct drm_connector_funcs apple_connector_funcs = {
 	.detect			= apple_connector_detect,
 	.debugfs_init		= apple_connector_debugfs_init,
 	.oob_hotplug_event	= apple_connector_oob_hotplug,
+	.late_register		= apple_connector_late_register,
+	.early_unregister	= apple_connector_early_unregister,
 };
 
 /*
@@ -325,6 +337,7 @@ static int apple_connector_create(struct drm_device *drm,
 		return -ENOMEM;
 
 	mutex_init(&connector->chunk_lock);
+	apple_connector_backlight_init(connector);
 	drm_connector_helper_add(&connector->base,
 				 &apple_connector_helper_funcs);
 	if (attach_fwnode)
@@ -466,6 +479,7 @@ static int apple_probe_typec_ports(struct drm_device *drm,
 			return -ENOMEM;
 
 		mutex_init(&connector->chunk_lock);
+		apple_connector_backlight_init(connector);
 		drm_connector_helper_add(&connector->base,
 					 &apple_connector_helper_funcs);
 

drivers/gpu/drm/apple/connector.h

@@ -17,6 +17,11 @@ struct apple_connector;
 void dcp_hotplug(struct work_struct *work);
 void dcp_retrain_oob(struct apple_connector *connector);
 
+void apple_connector_backlight_init(struct apple_connector *connector);
+void apple_connector_backlight_sync(struct apple_connector *connector);
+int apple_connector_backlight_late_register(struct apple_connector *connector);
+void apple_connector_backlight_early_unregister(struct apple_connector *connector);
+
 /*
  * How many DCP pipelines may offer a route to one Type-C port.  The Type-C mux
  * class caps the mode-switch providers per connector (TYPEC_MUX_MAX_DEVS) and
@@ -53,6 +58,16 @@ struct apple_connector {
 	struct dcp_chunks timing_elements;
 	struct dcp_chunks display_attributes;
 	struct dcp_chunks transport;
+
+	/*
+	 * Backlight of an external display that DCP can drive, registered
+	 * while such a display is connected.  bl_lock serialises
+	 * registration against the connector's sysfs lifetime.
+	 */
+	struct mutex bl_lock;
+	struct backlight_device *bl_dev;
+	bool bl_allowed;	/* between late_register and early_unregister */
+	int bl_level;		/* kept across replug, applied on every power-on */
 };
 
 #define to_apple_connector(x) container_of(x, struct apple_connector, base)

drivers/gpu/drm/apple/dcp-internal.h

@@ -250,6 +250,8 @@ struct apple_dcp {
 
 	/* Attributes of the connected display */
 	int width_mm, height_mm;
+	/* an external display whose backlight DCP can drive */
+	bool ext_backlight;
 
 	unsigned notch_height;
 
@@ -345,6 +347,7 @@ void dcp_handle_hotplug_actions(struct apple_dcp *dcp, unsigned int action);
 
 int dcp_backlight_register(struct apple_dcp *dcp);
 int dcp_backlight_update(struct apple_dcp *dcp);
+s32 dcp_ext_backlight_value(struct apple_dcp *dcp);
 bool dcp_has_panel(struct apple_dcp *dcp);
 
 #define DCP_AUDIO_MAX_CHANS 15

drivers/gpu/drm/apple/dcp.c

@@ -2193,6 +2193,8 @@ static void disconnected_hpd_event(struct apple_connector *con)
 		drm_edid_free(con->drm_edid);
 		con->drm_edid = NULL;
 		drm_kms_helper_connector_hotplug_event(&con->base);
+		/* drops the display's backlight, outside the caller's locks */
+		schedule_work(&con->hotplug_wq);
 	}
 }
 

drivers/gpu/drm/apple/dcp_backlight.c

@@ -5,12 +5,15 @@
 #include <drm/drm_crtc.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_modeset_lock.h>
+#include <drm/drm_print.h>
 
 #include <linux/backlight.h>
+#include <linux/math64.h>
 #include <linux/completion.h>
 #include <linux/delay.h>
 #include "linux/jiffies.h"
 
+#include "connector.h"
 #include "dcp.h"
 #include "dcp-internal.h"
 
@@ -256,3 +259,130 @@ int dcp_backlight_register(struct apple_dcp *dcp)
 
 	return 0;
 }
+
+/*
+ * External displays that report SupportsBacklightControl, such as the Apple
+ * Studio Display, take the same swap backlight fields as an integrated
+ * panel.  bl_value is then a signed 32-bit level from 0 (dimmest) to S32_MAX
+ * (brightest); DCP converts it for the display.  The backlight device belongs
+ * to the connector, so userspace can tell which output it dims.
+ */
+#define DCP_EXT_BL_MAX	1000
+
+/* The bl_value for the display on this DCP, or -1 if it has no backlight. */
+s32 dcp_ext_backlight_value(struct apple_dcp *dcp)
+{
+	struct apple_connector *connector = READ_ONCE(dcp->connector);
+
+	if (!connector || !READ_ONCE(dcp->ext_backlight))
+		return -1;
+
+	return div_u64((u64)READ_ONCE(connector->bl_level) * S32_MAX,
+		       DCP_EXT_BL_MAX);
+}
+
+static int dcp_ext_backlight_update_status(struct backlight_device *bd)
+{
+	struct apple_connector *connector = bl_get_data(bd);
+	struct platform_device *pdev;
+	struct apple_dcp *dcp;
+
+	WRITE_ONCE(connector->bl_level, backlight_get_brightness(bd));
+
+	/* An unrouted port picks the level up when it powers on again. */
+	pdev = READ_ONCE(connector->dcp);
+	if (!pdev)
+		return 0;
+
+	dcp = platform_get_drvdata(pdev);
+	/* pairs with the xchg() in iomfb_flush: it sees the level or leaves update set */
+	smp_store_release(&dcp->brightness.update, true);
+
+	return dcp_backlight_update(dcp);
+}
+
+static const struct backlight_ops dcp_ext_backlight_ops = {
+	.update_status = dcp_ext_backlight_update_status,
+};
+
+static void apple_connector_backlight_register(struct apple_connector *connector)
+{
+	struct backlight_properties props = {
+		.type = BACKLIGHT_RAW,
+		.max_brightness = DCP_EXT_BL_MAX,
+		.brightness = connector->bl_level,
+	};
+	struct backlight_device *bd;
+	char name[32];
+
+	snprintf(name, sizeof(name), "apple-%s-bl", connector->base.name);
+	bd = backlight_device_register(name, connector->base.kdev, connector,
+				       &dcp_ext_backlight_ops, &props);
+	if (IS_ERR(bd)) {
+		drm_warn(connector->base.dev,
+			 "%s: failed to register backlight: %pe\n",
+			 connector->base.name, bd);
+		return;
+	}
+
+	connector->bl_dev = bd;
+}
+
+static void apple_connector_backlight_unregister(struct apple_connector *connector)
+{
+	backlight_device_unregister(connector->bl_dev);
+	connector->bl_dev = NULL;
+}
+
+void apple_connector_backlight_init(struct apple_connector *connector)
+{
+	mutex_init(&connector->bl_lock);
+	connector->bl_level = DCP_EXT_BL_MAX;
+}
+
+/*
+ * Register the backlight while a display that supports it is connected, and
+ * drop it otherwise.  Called from the connector's hotplug work.
+ */
+void apple_connector_backlight_sync(struct apple_connector *connector)
+{
+	struct platform_device *pdev;
+	bool want = false;
+
+	mutex_lock(&connector->bl_lock);
+
+	pdev = READ_ONCE(connector->dcp);
+	if (connector->bl_allowed && READ_ONCE(connector->connected) && pdev) {
+		struct apple_dcp *dcp = platform_get_drvdata(pdev);
+
+		want = READ_ONCE(dcp->ext_backlight);
+	}
+
+	if (want && !connector->bl_dev)
+		apple_connector_backlight_register(connector);
+	else if (!want && connector->bl_dev)
+		apple_connector_backlight_unregister(connector);
+
+	mutex_unlock(&connector->bl_lock);
+}
+
+int apple_connector_backlight_late_register(struct apple_connector *connector)
+{
+	mutex_lock(&connector->bl_lock);
+	connector->bl_allowed = true;
+	mutex_unlock(&connector->bl_lock);
+
+	/* a display may have connected before the connector was registered */
+	apple_connector_backlight_sync(connector);
+
+	return 0;
+}
+
+void apple_connector_backlight_early_unregister(struct apple_connector *connector)
+{
+	mutex_lock(&connector->bl_lock);
+	connector->bl_allowed = false;
+	if (connector->bl_dev)
+		apple_connector_backlight_unregister(connector);
+	mutex_unlock(&connector->bl_lock);
+}

drivers/gpu/drm/apple/iomfb.c

@@ -292,6 +292,8 @@ void dcp_hotplug(struct work_struct *work)
 
 	connector = container_of(work, struct apple_connector, hotplug_wq);
 
+	apple_connector_backlight_sync(connector);
+
 	pdev = READ_ONCE(connector->dcp);
 	if (!pdev) {	/* a Type-C port unrouted after this was queued */
 		drm_kms_helper_connector_hotplug_event(&connector->base);

drivers/gpu/drm/apple/iomfb_template.c

@@ -592,14 +592,18 @@ static bool dcpep_process_chunks(struct apple_dcp *dcp,
 		if (dcp->nr_modes == 0)
 			dev_warn(dcp->dev, "TimingElements without valid modes!\n");
 	} else if (!strcmp(req->key, "DisplayAttributes")) {
+		bool backlight_control;
+
 		ret = parse_display_attributes(&ctx, &dcp->width_mm,
-					&dcp->height_mm);
+					&dcp->height_mm, &backlight_control);
 
 		if (ret) {
 			dev_warn(dcp->dev, "failed to parse display attribs\n");
 			return false;
 		}
 
+		WRITE_ONCE(dcp->ext_backlight,
+			   backlight_control && !dcp_has_panel(dcp));
 		dcp_set_dimensions(dcp);
 	}
 
@@ -1486,6 +1490,15 @@ void DCP_FW_NAME(iomfb_flush)(struct apple_dcp *dcp, struct drm_crtc *crtc, stru
 		req->swap.bl_value = dcp->brightness.dac;
 		req->swap.bl_power = 0x40;
 		dcp->brightness.update = false;
+	} else if (!dcp_has_panel(dcp) && xchg(&dcp->brightness.update, false)) {
+		/* read after clearing: a newer level sets update again and commits */
+		s32 bl = dcp_ext_backlight_value(dcp);
+
+		if (bl >= 0) {
+			req->swap.bl_unk = 1;
+			req->swap.bl_value = bl;
+			req->swap.bl_power = 0x40;
+		}
 	}
 
 	if (crtc_state->color_mgmt_changed) {

drivers/gpu/drm/apple/parser.c

@@ -615,12 +615,14 @@ struct dcp_display_mode *enumerate_modes(struct dcp_parse_ctx *handle,
 }
 
 int parse_display_attributes(struct dcp_parse_ctx *handle, int *width_mm,
-			     int *height_mm)
+			     int *height_mm, bool *backlight_control)
 {
 	int ret = 0;
 	struct iterator it;
 	s64 width_cm = 0, height_cm = 0;
 
+	*backlight_control = false;
+
 	dcp_parse_foreach_in_dict(handle, it) {
 		char *key = parse_string(it.handle);
 
@@ -630,6 +632,8 @@ int parse_display_attributes(struct dcp_parse_ctx *handle, int *width_mm,
 			ret = parse_int(it.handle, &width_cm);
 		else if (!strcmp(key, "MaxVerticalImageSize"))
 			ret = parse_int(it.handle, &height_cm);
+		else if (!strcmp(key, "SupportsBacklightControl"))
+			ret = parse_bool(it.handle, backlight_control);
 		else
 			skip(it.handle);
 

drivers/gpu/drm/apple/parser.h

@@ -107,7 +107,7 @@ struct dcp_display_mode *enumerate_modes(struct dcp_parse_ctx *handle,
 					 int height_mm, unsigned notch_height,
 					 bool internal);
 int parse_display_attributes(struct dcp_parse_ctx *handle, int *width_mm,
-			     int *height_mm);
+			     int *height_mm, bool *backlight_control);
 int parse_epic_service_init(struct dcp_parse_ctx *handle, const char **name,
 			    const char **class, s64 *unit);
 

drivers/pci/controller/pcie-apple.c

@@ -2191,6 +2191,11 @@ static int apple_pcie_tunnel_add_link(struct apple_pcie *pcie,
  * that suspends before a power-cycled display's hub reconnects never sees
  * the hub. Hold a runtime PM reference for as long as each function exists,
  * so that neither its driver nor power/control can suspend it.
+ *
+ * Keep the root port's link out of ASPM L1, too. Pulling the cable while
+ * the link idles in L1 wedges the root port: every later cold init leaves
+ * it unable to train, until the SoC is reset. The root port is added before
+ * the bus behind it is scanned, so ASPM never enables L1 on its link.
  */
 static int apple_pcie_tunnel_pci_notify(struct notifier_block *nb,
 					unsigned long action, void *data)
@@ -2205,6 +2210,8 @@ static int apple_pcie_tunnel_pci_notify(struct notifier_block *nb,
 	switch (action) {
 	case BUS_NOTIFY_ADD_DEVICE:
 		pm_runtime_get_noresume(&pdev->dev);
+		if (pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT)
+			pcie_aspm_remove_cap(pdev, PCI_EXP_LNKCAP_ASPM_L1);
 		break;
 	case BUS_NOTIFY_DEL_DEVICE:
 		pm_runtime_put_noidle(&pdev->dev);

drivers/pci/pcie/aspm.c

@@ -1545,6 +1545,7 @@ void pcie_aspm_remove_cap(struct pci_dev *pdev, u32 lnkcap)
 		 lnkcap & PCI_EXP_LNKCAP_ASPM_L1 ? " L1" : "");
 
 }
+EXPORT_SYMBOL_GPL(pcie_aspm_remove_cap);
 
 static int pcie_aspm_set_policy(const char *val,
 				const struct kernel_param *kp)