Re: [RFC PATCH 3/5] drm/i915: register LVDS connector even if we can't get a panel mode

[Seth Forshee <seth.forshee@canonical.com>]

On Mon, Aug 06, 2012 at 07:44:16AM +1000, Dave Airlie wrote:
> >> The "correct" approach is clearly to just have the drm core change the
> >> i2c mux before requesting edid, but that's made difficult because of the
> >> absence of ordering guarantees in initialisation. I don't like quirking
> >> this, since we're then back to the situation of potentially having to
> >> add every new piece of related hardware to the quirk list.
> >
> > The "correct" approach of switching the mux before we fetch the edid is
> > actualy the one I fear will result in fragile code: Only run on few
> > machines, and as you say with tons of funky interactions with the init
> > sequence ordering. And I guess people will bitch&moan about the flickering
> > this will cause ;-)
> >
> > As long as it's only apple shipping multi-gpu machines with
> > broken/non-existing vbt, I'll happily stomach the quirk list entries.
> > They're bad, but imo the lesser evil.
> 
> Well in theory you can switch the ddc lines without switching the other lines,
> so we could do a mutex protected mux switch around edid retrival,
> 
> Of course someone would have to code it up first then we could see how
> ugly it would be.

I coded it up, and it's not really too bad. I've put a dump of my local
changes below. But there are a couple of problems.

First, I don't have a solution for the ordering of initialization. It
just happens to work out for me right now.

Even so, the code only works if I delay loading i915. apple-gmux is
definitely initializing first so the i2c mux should be getting switched,
but the transactions are failing.

[   19.445658] [drm:gmbus_xfer], GMBUS [i915 gmbus panel] timed out after NAK 
[   19.445672] [drm:gmbus_xfer], GMBUS [i915 gmbus panel] NAK for addr: 0050 r(1) 

But if I prevent i915 from being auto-loaded and load later on it works
fine. I haven't been able to figure out what's going on. Any ideas?

Thanks,
Seth


diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index a8743c3..3f18e8a 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -31,6 +31,7 @@
 #include <linux/slab.h>
 #include <linux/i2c.h>
 #include <linux/module.h>
+#include <linux/vga_switcheroo.h>
 #include "drmP.h"
 #include "drm_edid.h"
 #include "drm_edid_modes.h"
@@ -82,6 +83,8 @@ struct detailed_mode_closure {
 #define LEVEL_GTF2	2
 #define LEVEL_CVT	3
 
+static DEFINE_MUTEX(drm_edid_mutex);
+
 static struct edid_quirk {
 	char vendor[4];
 	int product_id;
@@ -395,12 +398,25 @@ struct edid *drm_get_edid(struct drm_connector *connector,
 			  struct i2c_adapter *adapter)
 {
 	struct edid *edid = NULL;
+	struct pci_dev *pdev = connector->dev->pdev;
+	struct pci_dev *active_pdev = NULL;
+
+	mutex_lock(&drm_edid_mutex);
+
+	if (pdev) {
+		active_pdev = vga_switcheroo_get_active_client();
+		vga_switcheroo_switch_ddc(pdev);
+	}
 
 	if (drm_probe_ddc(adapter))
 		edid = (struct edid *)drm_do_get_edid(connector, adapter);
 
+	if (active_pdev)
+		vga_switcheroo_switch_ddc(active_pdev);
+
 	connector->display_info.raw_edid = (char *)edid;
 
+	mutex_unlock(&drm_edid_mutex);
 	return edid;
 
 }
diff --git a/drivers/gpu/vga/vga_switcheroo.c b/drivers/gpu/vga/vga_switcheroo.c
index e25cf31..e53f67d 100644
--- a/drivers/gpu/vga/vga_switcheroo.c
+++ b/drivers/gpu/vga/vga_switcheroo.c
@@ -205,6 +205,20 @@ find_active_client(struct list_head *head)
 	return NULL;
 }
 
+struct pci_dev *vga_switcheroo_get_active_client(void)
+{
+	struct vga_switcheroo_client *client;
+	struct pci_dev *pdev = NULL;
+
+	mutex_lock(&vgasr_mutex);
+	client = find_active_client(&vgasr_priv.clients);
+	if (client)
+		pdev = client->pdev;
+	mutex_unlock(&vgasr_mutex);
+	return pdev;
+}
+EXPORT_SYMBOL(vga_switcheroo_get_active_client);
+
 int vga_switcheroo_get_client_state(struct pci_dev *pdev)
 {
 	struct vga_switcheroo_client *client;
@@ -252,6 +266,29 @@ void vga_switcheroo_client_fb_set(struct pci_dev *pdev,
 }
 EXPORT_SYMBOL(vga_switcheroo_client_fb_set);
 
+int vga_switcheroo_switch_ddc(struct pci_dev *pdev)
+{
+	int ret = 0;
+	int id;
+
+	mutex_lock(&vgasr_mutex);
+
+	if (!vgasr_priv.handler) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	if (vgasr_priv.handler->switch_ddc) {
+		id = vgasr_priv.handler->get_client_id(pdev);
+		ret = vgasr_priv.handler->switch_ddc(id);
+	}
+
+out:
+	mutex_unlock(&vgasr_mutex);
+	return ret;
+}
+EXPORT_SYMBOL(vga_switcheroo_switch_ddc);
+
 static int vga_switcheroo_show(struct seq_file *m, void *v)
 {
 	struct vga_switcheroo_client *client;
@@ -342,9 +379,15 @@ static int vga_switchto_stage2(struct vga_switcheroo_client *new_client)
 		fb_notifier_call_chain(FB_EVENT_REMAP_ALL_CONSOLE, &event);
 	}
 
+	if (vgasr_priv.handler->switch_ddc) {
+		ret = vgasr_priv.handler->switch_ddc(new_client->id);
+		if (ret)
+			return ret;
+	}
+
 	ret = vgasr_priv.handler->switchto(new_client->id);
 	if (ret)
-		return ret;
+		goto restore_ddc;
 
 	if (new_client->ops->reprobe)
 		new_client->ops->reprobe(new_client->pdev);
@@ -356,6 +399,14 @@ static int vga_switchto_stage2(struct vga_switcheroo_client *new_client)
 
 	new_client->active = true;
 	return 0;
+
+restore_ddc:
+	if (vgasr_priv.handler->switch_ddc) {
+		int id = (new_client->id == VGA_SWITCHEROO_IGD) ?
+				VGA_SWITCHEROO_DIS : VGA_SWITCHEROO_IGD;
+		ret = vgasr_priv.handler->switch_ddc(id);
+	}
+	return ret;
 }
 
 static bool check_can_switch(void)
diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c
index 8ea2640..38f49fb 100644
--- a/drivers/platform/x86/apple-gmux.c
+++ b/drivers/platform/x86/apple-gmux.c
@@ -122,14 +122,21 @@ static const struct backlight_ops gmux_bl_ops = {
 	.update_status = gmux_update_status,
 };
 
+static int gmux_switchddc(enum vga_switcheroo_client_id id)
+{
+	if (id == VGA_SWITCHEROO_IGD)
+		gmux_write8(apple_gmux_data, GMUX_PORT_SWITCH_DDC, 1);
+	else
+		gmux_write8(apple_gmux_data, GMUX_PORT_SWITCH_DDC, 2);
+	return 0;
+}
+
 static int gmux_switchto(enum vga_switcheroo_client_id id)
 {
 	if (id == VGA_SWITCHEROO_IGD) {
-		gmux_write8(apple_gmux_data, GMUX_PORT_SWITCH_DDC, 1);
 		gmux_write8(apple_gmux_data, GMUX_PORT_SWITCH_DISPLAY, 2);
 		gmux_write8(apple_gmux_data, GMUX_PORT_SWITCH_EXTERNAL, 2);
 	} else {
-		gmux_write8(apple_gmux_data, GMUX_PORT_SWITCH_DDC, 2);
 		gmux_write8(apple_gmux_data, GMUX_PORT_SWITCH_DISPLAY, 3);
 		gmux_write8(apple_gmux_data, GMUX_PORT_SWITCH_EXTERNAL, 3);
 	}
@@ -196,6 +203,7 @@ gmux_active_client(struct apple_gmux_data *gmux_data)
 }
 
 static struct vga_switcheroo_handler gmux_handler = {
+	.switch_ddc = gmux_switchddc,
 	.switchto = gmux_switchto,
 	.power_state = gmux_set_power_state,
 	.get_client_id = gmux_get_client_id,
diff --git a/include/linux/vga_switcheroo.h b/include/linux/vga_switcheroo.h
index ddb419c..e361858 100644
--- a/include/linux/vga_switcheroo.h
+++ b/include/linux/vga_switcheroo.h
@@ -29,6 +29,7 @@ enum vga_switcheroo_client_id {
 };
 
 struct vga_switcheroo_handler {
+	int (*switch_ddc)(enum vga_switcheroo_client_id id);
 	int (*switchto)(enum vga_switcheroo_client_id id);
 	int (*power_state)(enum vga_switcheroo_client_id id,
 			   enum vga_switcheroo_state state);
@@ -53,11 +54,14 @@ int vga_switcheroo_register_audio_client(struct pci_dev *pdev,
 void vga_switcheroo_client_fb_set(struct pci_dev *dev,
 				  struct fb_info *info);
 
+int vga_switcheroo_switch_ddc(struct pci_dev *pdev);
+
 int vga_switcheroo_register_handler(struct vga_switcheroo_handler *handler);
 void vga_switcheroo_unregister_handler(void);
 
 int vga_switcheroo_process_delayed_switch(void);
 
+struct pci_dev *vga_switcheroo_get_active_client(void);
 int vga_switcheroo_get_client_state(struct pci_dev *dev);
 
 #else
@@ -66,12 +70,14 @@ static inline void vga_switcheroo_unregister_client(struct pci_dev *dev) {}
 static inline int vga_switcheroo_register_client(struct pci_dev *dev,
 		const struct vga_switcheroo_client_ops *ops) { return 0; }
 static inline void vga_switcheroo_client_fb_set(struct pci_dev *dev, struct fb_info *info) {}
+static inline void vga_switcheroo_switch_ddc(struct pci_dev *pdev) { return NULL; }
 static inline int vga_switcheroo_register_handler(struct vga_switcheroo_handler *handler) { return 0; }
 static inline int vga_switcheroo_register_audio_client(struct pci_dev *pdev,
 	const struct vga_switcheroo_client_ops *ops,
 	int id, bool active) { return 0; }
 static inline void vga_switcheroo_unregister_handler(void) {}
 static inline int vga_switcheroo_process_delayed_switch(void) { return 0; }
+static inline struct pci_dev *vga_switcheroo_get_active_client(void) { return NULL; }
 static inline int vga_switcheroo_get_client_state(struct pci_dev *dev) { return VGA_SWITCHEROO_ON; }