linux/drivers/gpu/drm/nouveau/nouveau_vga.c
Daniel Vetter fc8fd40eb2 drm: Rip out totally bogus vga_switcheroo->can_switch locking
So I just wanted to add a new field to struct drm_device and
accidentally stumbled over something. According to comments
dev->open_count is protected by dev->count_lock, but that's totally
not the case. It's protected by drm_global_mutex.

Unfortunately the vga switcheroo callbacks took this comment at face
value. The problem is that we can't just take the drm_global_mutex
because:
- It would lead to a locking inversion with the driver load/unload
  paths.
- It wouldn't actually protect anything, for that we'd need to wrap
  the entire vga switcheroo code in the drm_global_mutex. And I'm not
  sure whether that would actually solve anything.

What we probably want is a try_to_grab_switcheroo reference kind of
thing which is used in the driver's ->open callback. Then we could
move all that ->can_switch madness into the vga switcheroo core where
it really belongs.

But since that would amount to real work take the easy way out and
just add a comment. It's definitely not going to make anything worse
since doing switcheroo state changes while restarting X just isn't
recommended. Even though the delayed switching code does exactly that.

v2:
- Simplify the ->can_switch implementations more (Thierry)
- Fix comment about the dev->open_count locking (Thierry)

Cc: Thierry Reding <treding@nvidia.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> (v1)
Reviewed-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2014-04-23 10:32:33 +02:00

119 lines
3.1 KiB
C

#include <linux/vgaarb.h>
#include <linux/vga_switcheroo.h>
#include <drm/drmP.h>
#include <drm/drm_crtc_helper.h>
#include "nouveau_drm.h"
#include "nouveau_acpi.h"
#include "nouveau_fbcon.h"
#include "nouveau_vga.h"
static unsigned int
nouveau_vga_set_decode(void *priv, bool state)
{
struct nouveau_device *device = nouveau_dev(priv);
if (device->card_type == NV_40 && device->chipset >= 0x4c)
nv_wr32(device, 0x088060, state);
else if (device->chipset >= 0x40)
nv_wr32(device, 0x088054, state);
else
nv_wr32(device, 0x001854, state);
if (state)
return VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM |
VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM;
else
return VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM;
}
static void
nouveau_switcheroo_set_state(struct pci_dev *pdev,
enum vga_switcheroo_state state)
{
struct drm_device *dev = pci_get_drvdata(pdev);
if ((nouveau_is_optimus() || nouveau_is_v1_dsm()) && state == VGA_SWITCHEROO_OFF)
return;
if (state == VGA_SWITCHEROO_ON) {
printk(KERN_ERR "VGA switcheroo: switched nouveau on\n");
dev->switch_power_state = DRM_SWITCH_POWER_CHANGING;
nouveau_pmops_resume(&pdev->dev);
drm_kms_helper_poll_enable(dev);
dev->switch_power_state = DRM_SWITCH_POWER_ON;
} else {
printk(KERN_ERR "VGA switcheroo: switched nouveau off\n");
dev->switch_power_state = DRM_SWITCH_POWER_CHANGING;
drm_kms_helper_poll_disable(dev);
nouveau_switcheroo_optimus_dsm();
nouveau_pmops_suspend(&pdev->dev);
dev->switch_power_state = DRM_SWITCH_POWER_OFF;
}
}
static void
nouveau_switcheroo_reprobe(struct pci_dev *pdev)
{
struct drm_device *dev = pci_get_drvdata(pdev);
nouveau_fbcon_output_poll_changed(dev);
}
static bool
nouveau_switcheroo_can_switch(struct pci_dev *pdev)
{
struct drm_device *dev = pci_get_drvdata(pdev);
/*
* FIXME: open_count is protected by drm_global_mutex but that would lead to
* locking inversion with the driver load path. And the access here is
* completely racy anyway. So don't bother with locking for now.
*/
return dev->open_count == 0;
}
static const struct vga_switcheroo_client_ops
nouveau_switcheroo_ops = {
.set_gpu_state = nouveau_switcheroo_set_state,
.reprobe = nouveau_switcheroo_reprobe,
.can_switch = nouveau_switcheroo_can_switch,
};
void
nouveau_vga_init(struct nouveau_drm *drm)
{
struct drm_device *dev = drm->dev;
bool runtime = false;
/* only relevant for PCI devices */
if (!dev->pdev)
return;
vga_client_register(dev->pdev, dev, NULL, nouveau_vga_set_decode);
if (nouveau_runtime_pm == 1)
runtime = true;
if ((nouveau_runtime_pm == -1) && (nouveau_is_optimus() || nouveau_is_v1_dsm()))
runtime = true;
vga_switcheroo_register_client(dev->pdev, &nouveau_switcheroo_ops, runtime);
if (runtime && nouveau_is_v1_dsm() && !nouveau_is_optimus())
vga_switcheroo_init_domain_pm_ops(drm->dev->dev, &drm->vga_pm_domain);
}
void
nouveau_vga_fini(struct nouveau_drm *drm)
{
struct drm_device *dev = drm->dev;
vga_switcheroo_unregister_client(dev->pdev);
vga_client_register(dev->pdev, NULL, NULL, NULL);
}
void
nouveau_vga_lastclose(struct drm_device *dev)
{
vga_switcheroo_process_delayed_switch();
}