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[RFC,3/9] apple-gmux: use first bit to check switch state

Message ID 20230210044826.9834-4-orlandoch.dev@gmail.com (mailing list archive)
State New, archived
Headers show
Series apple-gmux: support MMIO gmux type on T2 Macs | expand

Commit Message

Orlando Chamberlain Feb. 10, 2023, 4:48 a.m. UTC 
On T2 Macs with MMIO gmux, when GMUX_PORT_SWITCH_DISPLAY is read, it can
have values of 2, 3, 4, and 5. Odd values correspond to the discrete gpu,
and even values correspond to the integrated gpu. The current logic is
that only 2 corresponds to IGD, but this doesn't work for T2 Macs.
Instead, check the first bit to determine the connected gpu.

As T2 Macs with gmux only can switch the internal display, it is
untested if this change (or a similar change) would be applicable
to GMUX_PORT_SWITCH_DDC and GMUX_PORT_SWITCH_EXTERNAL.

Signed-off-by: Orlando Chamberlain <orlandoch.dev@gmail.com>
---
 drivers/platform/x86/apple-gmux.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c
index 67628104f31a..6109f4c2867c 100644
--- a/drivers/platform/x86/apple-gmux.c
+++ b/drivers/platform/x86/apple-gmux.c
@@ -332,10 +332,10 @@  static void gmux_read_switch_state(struct apple_gmux_data *gmux_data)
 	else
 		gmux_data->switch_state_ddc = VGA_SWITCHEROO_DIS;
 
-	if (gmux_read8(gmux_data, GMUX_PORT_SWITCH_DISPLAY) == 2)
-		gmux_data->switch_state_display = VGA_SWITCHEROO_IGD;
-	else
+	if (gmux_read8(gmux_data, GMUX_PORT_SWITCH_DISPLAY) & 1)
 		gmux_data->switch_state_display = VGA_SWITCHEROO_DIS;
+	else
+		gmux_data->switch_state_display = VGA_SWITCHEROO_IGD;
 
 	if (gmux_read8(gmux_data, GMUX_PORT_SWITCH_EXTERNAL) == 2)
 		gmux_data->switch_state_external = VGA_SWITCHEROO_IGD;