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authorBernhard Froemel <froemel@vmars.tuwien.ac.at>2012-08-25 10:30:48 +0200
committerMatthew Garrett <mjg@redhat.com>2012-09-13 16:46:29 -0400
commitc5a5052923c55990e32a3d64bdb4779b01162646 (patch)
tree6ffd57a7eba842cd14d18479f540fefabe9eb44f /drivers/platform/x86/apple-gmux.c
parent07f377da7e8a7d3c3a6626333516f9c808637c9e (diff)
downloadlinux-linaro-stable-c5a5052923c55990e32a3d64bdb4779b01162646.tar.gz
apple-gmux: Fix index read functions
Study of Apple's binary driver revealed that the GMUX_READ_PORT should be written between calls to gmux_index_wait_ready and gmux_index_wait_complete (i.e., the new index protocol must be followed). If this is not done correctly, the indexed gmux device only partially accepts writes which lead to problems concerning GPU switching. Special thanks to Seth Forshee who helped greatly with identifying unnecessary changes. Signed-off-by: Bernhard Froemel <froemel@vmars.tuwien.ac.at> Signed-off-by: Matthew Garrett <mjg@redhat.com>
Diffstat (limited to 'drivers/platform/x86/apple-gmux.c')
-rw-r--r--drivers/platform/x86/apple-gmux.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c
index c9558d1ea88c..0e43477de337 100644
--- a/drivers/platform/x86/apple-gmux.c
+++ b/drivers/platform/x86/apple-gmux.c
@@ -142,8 +142,9 @@ static u8 gmux_index_read8(struct apple_gmux_data *gmux_data, int port)
u8 val;
mutex_lock(&gmux_data->index_lock);
- outb((port & 0xff), gmux_data->iostart + GMUX_PORT_READ);
gmux_index_wait_ready(gmux_data);
+ outb((port & 0xff), gmux_data->iostart + GMUX_PORT_READ);
+ gmux_index_wait_complete(gmux_data);
val = inb(gmux_data->iostart + GMUX_PORT_VALUE);
mutex_unlock(&gmux_data->index_lock);
@@ -166,8 +167,9 @@ static u32 gmux_index_read32(struct apple_gmux_data *gmux_data, int port)
u32 val;
mutex_lock(&gmux_data->index_lock);
- outb((port & 0xff), gmux_data->iostart + GMUX_PORT_READ);
gmux_index_wait_ready(gmux_data);
+ outb((port & 0xff), gmux_data->iostart + GMUX_PORT_READ);
+ gmux_index_wait_complete(gmux_data);
val = inl(gmux_data->iostart + GMUX_PORT_VALUE);
mutex_unlock(&gmux_data->index_lock);