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apple-gmux: Fix index read functions

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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>
This commit is contained in:
Bernhard Froemel 2012-08-25 10:30:48 +02:00 committed by Matthew Garrett
parent 07f377da7e
commit c5a5052923
1 changed files with 4 additions and 2 deletions
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6
drivers/platform/x86/apple-gmux.c
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@ -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);