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-rw-r--r--drivers/gpu/vga/vga_switcheroo.c97
-rw-r--r--include/linux/vga_switcheroo.h8
2 files changed, 103 insertions, 2 deletions
diff --git a/drivers/gpu/vga/vga_switcheroo.c b/drivers/gpu/vga/vga_switcheroo.c
index e89f6ad5d83e..cbd7c986d926 100644
--- a/drivers/gpu/vga/vga_switcheroo.c
+++ b/drivers/gpu/vga/vga_switcheroo.c
@@ -74,9 +74,17 @@
* there can thus be up to three clients: Two vga clients (GPUs) and one audio
* client (on the discrete GPU). The code is mostly prepared to support
* machines with more than two GPUs should they become available.
+ *
* The GPU to which the outputs are currently switched is called the
* active client in vga_switcheroo parlance. The GPU not in use is the
- * inactive client.
+ * inactive client. When the inactive client's DRM driver is loaded,
+ * it will be unable to probe the panel's EDID and hence depends on
+ * VBIOS to provide its display modes. If the VBIOS modes are bogus or
+ * if there is no VBIOS at all (which is common on the MacBook Pro),
+ * a client may alternatively request that the DDC lines are temporarily
+ * switched to it, provided that the handler supports this. Switching
+ * only the DDC lines and not the entire output avoids unnecessary
+ * flickering.
*/
/**
@@ -127,6 +135,9 @@ static DEFINE_MUTEX(vgasr_mutex);
* @clients: list of registered clients
* @handler: registered handler
* @handler_flags: flags of registered handler
+ * @mux_hw_lock: protects mux state
+ * (in particular while DDC lines are temporarily switched)
+ * @old_ddc_owner: client to which DDC lines will be switched back on unlock
*
* vga_switcheroo private data. Currently only one vga_switcheroo instance
* per system is supported.
@@ -144,6 +155,8 @@ struct vgasr_priv {
const struct vga_switcheroo_handler *handler;
enum vga_switcheroo_handler_flags_t handler_flags;
+ struct mutex mux_hw_lock;
+ int old_ddc_owner;
};
#define ID_BIT_AUDIO 0x100
@@ -158,6 +171,7 @@ static void vga_switcheroo_debugfs_fini(struct vgasr_priv *priv);
/* only one switcheroo per system */
static struct vgasr_priv vgasr_priv = {
.clients = LIST_HEAD_INIT(vgasr_priv.clients),
+ .mux_hw_lock = __MUTEX_INITIALIZER(vgasr_priv.mux_hw_lock),
};
static bool vga_switcheroo_ready(void)
@@ -227,6 +241,7 @@ EXPORT_SYMBOL(vga_switcheroo_register_handler);
void vga_switcheroo_unregister_handler(void)
{
mutex_lock(&vgasr_mutex);
+ mutex_lock(&vgasr_priv.mux_hw_lock);
vgasr_priv.handler_flags = 0;
vgasr_priv.handler = NULL;
if (vgasr_priv.active) {
@@ -234,6 +249,7 @@ void vga_switcheroo_unregister_handler(void)
vga_switcheroo_debugfs_fini(&vgasr_priv);
vgasr_priv.active = false;
}
+ mutex_unlock(&vgasr_priv.mux_hw_lock);
mutex_unlock(&vgasr_mutex);
}
EXPORT_SYMBOL(vga_switcheroo_unregister_handler);
@@ -433,6 +449,76 @@ void vga_switcheroo_client_fb_set(struct pci_dev *pdev,
EXPORT_SYMBOL(vga_switcheroo_client_fb_set);
/**
+ * vga_switcheroo_lock_ddc() - temporarily switch DDC lines to a given client
+ * @pdev: client pci device
+ *
+ * Temporarily switch DDC lines to the client identified by @pdev
+ * (but leave the outputs otherwise switched to where they are).
+ * This allows the inactive client to probe EDID. The DDC lines must
+ * afterwards be switched back by calling vga_switcheroo_unlock_ddc(),
+ * even if this function returns an error.
+ *
+ * Return: Previous DDC owner on success or a negative int on error.
+ * Specifically, %-ENODEV if no handler has registered or if the handler
+ * does not support switching the DDC lines. Also, a negative value
+ * returned by the handler is propagated back to the caller.
+ * The return value has merely an informational purpose for any caller
+ * which might be interested in it. It is acceptable to ignore the return
+ * value and simply rely on the result of the subsequent EDID probe,
+ * which will be %NULL if DDC switching failed.
+ */
+int vga_switcheroo_lock_ddc(struct pci_dev *pdev)
+{
+ enum vga_switcheroo_client_id id;
+
+ mutex_lock(&vgasr_priv.mux_hw_lock);
+ if (!vgasr_priv.handler || !vgasr_priv.handler->switch_ddc) {
+ vgasr_priv.old_ddc_owner = -ENODEV;
+ return -ENODEV;
+ }
+
+ id = vgasr_priv.handler->get_client_id(pdev);
+ vgasr_priv.old_ddc_owner = vgasr_priv.handler->switch_ddc(id);
+ return vgasr_priv.old_ddc_owner;
+}
+EXPORT_SYMBOL(vga_switcheroo_lock_ddc);
+
+/**
+ * vga_switcheroo_unlock_ddc() - switch DDC lines back to previous owner
+ * @pdev: client pci device
+ *
+ * Switch DDC lines back to the previous owner after calling
+ * vga_switcheroo_lock_ddc(). This must be called even if
+ * vga_switcheroo_lock_ddc() returned an error.
+ *
+ * Return: Previous DDC owner on success (i.e. the client identifier of @pdev)
+ * or a negative int on error.
+ * Specifically, %-ENODEV if no handler has registered or if the handler
+ * does not support switching the DDC lines. Also, a negative value
+ * returned by the handler is propagated back to the caller.
+ * Finally, invoking this function without calling vga_switcheroo_lock_ddc()
+ * first is not allowed and will result in %-EINVAL.
+ */
+int vga_switcheroo_unlock_ddc(struct pci_dev *pdev)
+{
+ enum vga_switcheroo_client_id id;
+ int ret = vgasr_priv.old_ddc_owner;
+
+ if (WARN_ON_ONCE(!mutex_is_locked(&vgasr_priv.mux_hw_lock)))
+ return -EINVAL;
+
+ if (vgasr_priv.old_ddc_owner >= 0) {
+ id = vgasr_priv.handler->get_client_id(pdev);
+ if (vgasr_priv.old_ddc_owner != id)
+ ret = vgasr_priv.handler->switch_ddc(
+ vgasr_priv.old_ddc_owner);
+ }
+ mutex_unlock(&vgasr_priv.mux_hw_lock);
+ return ret;
+}
+EXPORT_SYMBOL(vga_switcheroo_unlock_ddc);
+
+/**
* DOC: Manual switching and manual power control
*
* In this mode of use, the file /sys/kernel/debug/vgaswitcheroo/switch
@@ -569,7 +655,9 @@ static int vga_switchto_stage2(struct vga_switcheroo_client *new_client)
console_unlock();
}
+ mutex_lock(&vgasr_priv.mux_hw_lock);
ret = vgasr_priv.handler->switchto(new_client->id);
+ mutex_unlock(&vgasr_priv.mux_hw_lock);
if (ret)
return ret;
@@ -684,7 +772,9 @@ vga_switcheroo_debugfs_write(struct file *filp, const char __user *ubuf,
vgasr_priv.delayed_switch_active = false;
if (just_mux) {
+ mutex_lock(&vgasr_priv.mux_hw_lock);
ret = vgasr_priv.handler->switchto(client_id);
+ mutex_unlock(&vgasr_priv.mux_hw_lock);
goto out;
}
@@ -896,8 +986,11 @@ static int vga_switcheroo_runtime_suspend(struct device *dev)
if (ret)
return ret;
mutex_lock(&vgasr_mutex);
- if (vgasr_priv.handler->switchto)
+ if (vgasr_priv.handler->switchto) {
+ mutex_lock(&vgasr_priv.mux_hw_lock);
vgasr_priv.handler->switchto(VGA_SWITCHEROO_IGD);
+ mutex_unlock(&vgasr_priv.mux_hw_lock);
+ }
vga_switcheroo_power_switch(pdev, VGA_SWITCHEROO_OFF);
mutex_unlock(&vgasr_mutex);
return 0;
diff --git a/include/linux/vga_switcheroo.h b/include/linux/vga_switcheroo.h
index a745f4f0f729..b39a5f3153bd 100644
--- a/include/linux/vga_switcheroo.h
+++ b/include/linux/vga_switcheroo.h
@@ -102,6 +102,9 @@ enum vga_switcheroo_client_id {
* Mandatory. For muxless machines this should be a no-op. Returning 0
* denotes success, anything else failure (in which case the switch is
* aborted)
+ * @switch_ddc: switch DDC lines to given client.
+ * Optional. Should return the previous DDC owner on success or a
+ * negative int on failure
* @power_state: cut or reinstate power of given client.
* Optional. The return value is ignored
* @get_client_id: determine if given pci device is integrated or discrete GPU.
@@ -113,6 +116,7 @@ enum vga_switcheroo_client_id {
struct vga_switcheroo_handler {
int (*init)(void);
int (*switchto)(enum vga_switcheroo_client_id id);
+ int (*switch_ddc)(enum vga_switcheroo_client_id id);
int (*power_state)(enum vga_switcheroo_client_id id,
enum vga_switcheroo_state state);
enum vga_switcheroo_client_id (*get_client_id)(struct pci_dev *pdev);
@@ -156,6 +160,8 @@ int vga_switcheroo_register_handler(const struct vga_switcheroo_handler *handler
enum vga_switcheroo_handler_flags_t handler_flags);
void vga_switcheroo_unregister_handler(void);
enum vga_switcheroo_handler_flags_t vga_switcheroo_handler_flags(void);
+int vga_switcheroo_lock_ddc(struct pci_dev *pdev);
+int vga_switcheroo_unlock_ddc(struct pci_dev *pdev);
int vga_switcheroo_process_delayed_switch(void);
@@ -179,6 +185,8 @@ static inline int vga_switcheroo_register_audio_client(struct pci_dev *pdev,
enum vga_switcheroo_client_id id) { return 0; }
static inline void vga_switcheroo_unregister_handler(void) {}
static inline enum vga_switcheroo_handler_flags_t vga_switcheroo_handler_flags(void) { return 0; }
+static inline int vga_switcheroo_lock_ddc(struct pci_dev *pdev) { return -ENODEV; }
+static inline int vga_switcheroo_unlock_ddc(struct pci_dev *pdev) { return -ENODEV; }
static inline int vga_switcheroo_process_delayed_switch(void) { return 0; }
static inline enum vga_switcheroo_state vga_switcheroo_get_client_state(struct pci_dev *dev) { return VGA_SWITCHEROO_ON; }