It looks like the AST2400 comes up with the DVO enable bit set,
which causes us to incorrectly assume we have a SIL164 regardless
of the value of the scratch registers setup by the BMC firmware.
So let's limit that test to the case where the chip has already
been setup by a BIOS.
Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/ast/ast_main.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/ast/ast_main.c b/drivers/gpu/drm/ast/ast_main.c
index 556d065..48998b2 100644
--- a/drivers/gpu/drm/ast/ast_main.c
+++ b/drivers/gpu/drm/ast/ast_main.c
@@ -158,16 +158,22 @@ static int ast_detect_chip(struct drm_device *dev, bool *need_post)
/*
* VGACRA3 Enhanced Color Mode Register, check if DVO is already
* enabled, in that case, assume we have a SIL164 TMDS transmitter
+ *
+ * Don't make that assumption if we the chip wasn't enabled and
+ * is at power-on reset, otherwise we'll incorrectly "detect" a
+ * SIL164 when there is none.
*/
- jreg = ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xa3, 0xff);
- if (jreg & 0x80)
- ast->tx_chip_type = AST_TX_SIL164;
+ if (!*need_post) {
+ jreg = ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xa3, 0xff);
+ if (jreg & 0x80)
+ ast->tx_chip_type = AST_TX_SIL164;
+ }
if ((ast->chip == AST2300) || (ast->chip == AST2400)) {
/*
* On AST2300 and 2400, look the configuration set by the SoC in
* the SOC scratch register #1 bits 11:8 (interestingly marked
- * as "reserved" in the spec
+ * as "reserved" in the spec)
*/
jreg = ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xd1, 0xff);
switch (jreg) {
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