Commit e02328f4 authored by Lukas Wunner's avatar Lukas Wunner Committed by Dave Airlie
Browse files

vga_switcheroo: Drop client power state VGA_SWITCHEROO_INIT 

hda_intel.c:azx_probe() defers initialization of an audio controller
on the discrete GPU if the GPU is powered off. The power state of the
GPU is determined by calling vga_switcheroo_get_client_state().

vga_switcheroo_get_client_state() returns VGA_SWITCHEROO_INIT if
vga_switcheroo is not enabled, i.e. if no second GPU or no handler
has registered.

This can go wrong in the following scenario:
- Driver for the integrated GPU is not loaded.
- Driver for the discrete GPU registers with vga_switcheroo, uses driver
  power control to power down the GPU, handler cuts power to the GPU.
- Driver for the audio controller gets loaded after the GPU was powered
  down, calls vga_switcheroo_get_client_state() which returns
  VGA_SWITCHEROO_INIT instead of VGA_SWITCHEROO_OFF.
- Consequence: azx_probe() tries to initialize the audio controller even
  though the GPU is powered down.

The power state VGA_SWITCHEROO_INIT was introduced by c8e9cf7b
("vga_swit...
parent b26eae93

drivers/gpu/vga/vga_switcheroo.c

+0 −2
Original line number Diff line number Diff line
@@ -356,8 +356,6 @@ enum vga_switcheroo_state vga_switcheroo_get_client_state(struct pci_dev *pdev) 
	client = find_client_from_pci(&vgasr_priv.clients, pdev);

	if (!client)

		ret = VGA_SWITCHEROO_NOT_FOUND;

	else if (!vgasr_priv.active)

		ret = VGA_SWITCHEROO_INIT;

	else

		ret = client->pwr_state;

	mutex_unlock(&vgasr_mutex);

include/linux/vga_switcheroo.h

+0 −5
Original line number Diff line number Diff line
@@ -39,10 +39,6 @@ struct pci_dev; 
 * enum vga_switcheroo_state - client power state

 * @VGA_SWITCHEROO_OFF: off

 * @VGA_SWITCHEROO_ON: on

 * @VGA_SWITCHEROO_INIT: client has registered with vga_switcheroo but

 * 	vga_switcheroo is not enabled, i.e. no second client or no handler

 * 	has registered. Only used in vga_switcheroo_get_client_state() which

 * 	in turn is only called from hda_intel.c

 * @VGA_SWITCHEROO_NOT_FOUND: client has not registered with vga_switcheroo.

 * 	Only used in vga_switcheroo_get_client_state() which in turn is only

 * 	called from hda_intel.c
@@ -53,7 +49,6 @@ enum vga_switcheroo_state { 
	VGA_SWITCHEROO_OFF,

	VGA_SWITCHEROO_ON,

	/* below are referred only from vga_switcheroo_get_client_state() */

	VGA_SWITCHEROO_INIT,

	VGA_SWITCHEROO_NOT_FOUND,

};