Hi Gaele,
On Sun, Feb 14, 2016 at 12:39:12AM +0100, Lukas Wunner wrote:
> On dual GPU MacBook Pros, brightness is controlled by gmux.
> It is changed by writing to gmux' I/O port range, 0x700 - 0x7FF.
> gmux is located on the LPC bus, i.e. behind the southbridge.
>
> For communication with gmux to work, the above-mentioned I/O port
> range needs to be routed to bus 00, where the LPC bus bridge is
> located. Incidentally the integrated GPU is also located on that
> same bus, whereas the discrete GPU is on a different bus. (It is
> directly connected to the PCI Root Complex in the CPU.)
FWIW, I've cobbled together an experimental patch (included below)
which locks I/O to the LPC bridge instead of the integrated GPU.
This requires a modification to vgaarb.c to deal with not just
PCI_CLASS_DISPLAY_VGA, but also PCI_CLASS_BRIDGE_ISA devices.
As to the justification, well it *could* be argued that back in
the 1990s we had mainboards with PCI + ISA slots and for backward
compatibility we need to support VGA devices in ISA slots located
behind a PCI/ISA bridge. ;-)
Seriously though, maybe you want to give this a try and see if
it solves the issue for you (apply with git am --scissors).
Best regards,
Lukas
-- >8 --
Subject: [PATCH] apple-gmux: Fix IO locking
Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
---
drivers/gpu/vga/vgaarb.c | 3 ++-
drivers/platform/x86/apple-gmux.c | 51 ++++++++++++++-------------------------
2 files changed, 20 insertions(+), 34 deletions(-)
diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c
index f17cb04..b23b471 100644
--- a/drivers/gpu/vga/vgaarb.c
+++ b/drivers/gpu/vga/vgaarb.c
@@ -529,7 +529,8 @@ static bool vga_arbiter_add_pci_device(struct pci_dev *pdev)
u16 cmd;
/* Only deal with VGA class devices */
- if ((pdev->class >> 8) != PCI_CLASS_DISPLAY_VGA)
+ if ((pdev->class >> 8) != PCI_CLASS_DISPLAY_VGA &&
+ (pdev->class >> 8) != PCI_CLASS_BRIDGE_ISA)
return false;
/* Allocate structure */
diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c
index f236250..999daad 100644
--- a/drivers/platform/x86/apple-gmux.c
+++ b/drivers/platform/x86/apple-gmux.c
@@ -48,10 +48,10 @@
struct apple_gmux_data {
unsigned long iostart;
unsigned long iolen;
+ struct pci_dev *lpc_bridge;
bool indexed;
struct mutex index_lock;
- struct pci_dev *pdev;
struct backlight_device *bdev;
/* switcheroo data */
@@ -530,34 +530,17 @@ static int gmux_resume(struct device *dev)
return 0;
}
-static struct pci_dev *gmux_get_io_pdev(void)
-{
- struct pci_dev *pdev = NULL;
-
- while ((pdev = pci_get_class(PCI_CLASS_DISPLAY_VGA << 8, pdev))) {
- u16 cmd;
-
- pci_read_config_word(pdev, PCI_COMMAND, &cmd);
- if (!(cmd & PCI_COMMAND_IO))
- continue;
-
- return pdev;
- }
-
- return NULL;
-}
-
static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
{
struct apple_gmux_data *gmux_data;
struct resource *res;
+ struct pci_dev *lpc_bridge;
struct backlight_properties props;
struct backlight_device *bdev;
u8 ver_major, ver_minor, ver_release;
int ret = -ENXIO;
acpi_status status;
unsigned long long gpe;
- struct pci_dev *pdev = NULL;
if (apple_gmux_data)
return -EBUSY;
@@ -622,16 +605,17 @@ static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
* disables IO/MEM used for backlight control on some systems.
* Lock IO+MEM to GPU with active IO to prevent switch.
*/
- pdev = gmux_get_io_pdev();
- if (pdev && vga_tryget(pdev,
- VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM)) {
- pr_err("IO+MEM vgaarb-locking for PCI:%s failed\n",
- pci_name(pdev));
+ lpc_bridge = pci_get_class(PCI_CLASS_BRIDGE_ISA << 8, NULL);
+ if (lpc_bridge &&
+ !vga_tryget(lpc_bridge, VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM)) {
+ pr_debug("Locked IO to %s\n", pci_name(lpc_bridge));
+ gmux_data->lpc_bridge = lpc_bridge;
+ } else {
+ pr_err("Failed to lock IO to %s\n", pci_name(lpc_bridge));
+ pci_dev_put(lpc_bridge);
ret = -EBUSY;
goto err_release;
- } else if (pdev)
- pr_info("locked IO for PCI:%s\n", pci_name(pdev));
- gmux_data->pdev = pdev;
+ }
memset(&props, 0, sizeof(props));
props.type = BACKLIGHT_PLATFORM;
@@ -725,10 +709,11 @@ err_enable_gpe:
err_notify:
backlight_device_unregister(bdev);
err_release:
- if (gmux_data->pdev)
- vga_put(gmux_data->pdev,
+ if (gmux_data->lpc_bridge) {
+ vga_put(gmux_data->lpc_bridge,
VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM);
- pci_dev_put(pdev);
+ pci_dev_put(gmux_data->lpc_bridge);
+ }
release_region(gmux_data->iostart, gmux_data->iolen);
err_free:
kfree(gmux_data);
@@ -748,10 +733,10 @@ static void gmux_remove(struct pnp_dev *pnp)
&gmux_notify_handler);
}
- if (gmux_data->pdev) {
- vga_put(gmux_data->pdev,
+ if (gmux_data->lpc_bridge) {
+ vga_put(gmux_data->lpc_bridge,
VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM);
- pci_dev_put(gmux_data->pdev);
+ pci_dev_put(gmux_data->lpc_bridge);
}
backlight_device_unregister(gmux_data->bdev);
--
2.1.0
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