On 2/20/2014 10:23 AM, Jiang Liu wrote:
Fix regression caused by commit b072e53, which breaks loading nouveau
driver on optimus laptops.
On some platforms, ACPI _DSM method (nouveau_op_dsm_muid, function 0)
has special requirements on the fourth parameter, which is different
from ACPI specifications. So revert to the private implementation
to check availability of _DSM functions instead of using common
acpi_check_dsm() interface.
Reported-and-Tested-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxx>
Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx>
I'm taking this, because the commit that introduced the regression went
in through my tree.
In the future I'll appreciate CCing ACPI-related patches to linux-acpi,
however.
Thanks,
Rafael
---
drivers/gpu/drm/nouveau/nouveau_acpi.c | 26 ++++++++++++++++++++++++--
1 file changed, 24 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_acpi.c b/drivers/gpu/drm/nouveau/nouveau_acpi.c
index 4ef83df..83face3 100644
--- a/drivers/gpu/drm/nouveau/nouveau_acpi.c
+++ b/drivers/gpu/drm/nouveau/nouveau_acpi.c
@@ -106,6 +106,29 @@ static int nouveau_optimus_dsm(acpi_handle handle, int func, int arg, uint32_t *
return 0;
}
+/*
+ * On some platforms, _DSM(nouveau_op_dsm_muid, func0) has special
+ * requirements on the fourth parameter, so a private implementation
+ * instead of using acpi_check_dsm().
+ */
+static int nouveau_check_optimus_dsm(acpi_handle handle)
+{
+ int result;
+
+ /*
+ * Function 0 returns a Buffer containing available functions.
+ * The args parameter is ignored for function 0, so just put 0 in it
+ */
+ if (nouveau_optimus_dsm(handle, 0, 0, &result))
+ return 0;
+
+ /*
+ * ACPI Spec v4 9.14.1: if bit 0 is zero, no function is supported.
+ * If the n-th bit is enabled, function n is supported
+ */
+ return result & 1 && result & (1 << NOUVEAU_DSM_OPTIMUS_CAPS);
+}
+
static int nouveau_dsm(acpi_handle handle, int func, int arg)
{
int ret = 0;
@@ -207,8 +230,7 @@ static int nouveau_dsm_pci_probe(struct pci_dev *pdev)
1 << NOUVEAU_DSM_POWER))
retval |= NOUVEAU_DSM_HAS_MUX;
- if (acpi_check_dsm(dhandle, nouveau_op_dsm_muid, 0x00000100,
- 1 << NOUVEAU_DSM_OPTIMUS_CAPS))
+ if (nouveau_check_optimus_dsm(dhandle))
retval |= NOUVEAU_DSM_HAS_OPT;
if (retval & NOUVEAU_DSM_HAS_OPT) {
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