[PATCH] MIPS: disabling CM regions deadlocks mt7621

[John Crispin]

While updating the mt7621 code to make use of the mips-cm i had to apply the
following patch to get the unit booting. With this patch applied the SoC boots
fine with and all 4 cores work.

The MT7621 has a broken iocu so i guess this might be related ? could someone that
actually knows what those registers do enlighten me please :)

Signed-off-by: John Crispin <***@openwrt.org>
---
arch/mips/kernel/mips-cm.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/mips/kernel/mips-cm.c b/arch/mips/kernel/mips-cm.c
index f76f7a0..38835c2 100644
--- a/arch/mips/kernel/mips-cm.c
+++ b/arch/mips/kernel/mips-cm.c
@@ -105,6 +105,7 @@ int mips_cm_probe(void)
write_gcr_base(base_reg);

/* disable CM regions */
+ /*
write_gcr_reg0_base(CM_GCR_REGn_BASE_BASEADDR_MSK);
write_gcr_reg0_mask(CM_GCR_REGn_MASK_ADDRMASK_MSK);
write_gcr_reg1_base(CM_GCR_REGn_BASE_BASEADDR_MSK);
@@ -113,7 +114,7 @@ int mips_cm_probe(void)
write_gcr_reg2_mask(CM_GCR_REGn_MASK_ADDRMASK_MSK);
write_gcr_reg3_base(CM_GCR_REGn_BASE_BASEADDR_MSK);
write_gcr_reg3_mask(CM_GCR_REGn_MASK_ADDRMASK_MSK);
-
+ */
/* probe for an L2-only sync region */
mips_cm_probe_l2sync();

[Andrew Bresticker]

Hi John,

Post by John Crispin
While updating the mt7621 code to make use of the mips-cm i had to apply the
following patch to get the unit booting. With this patch applied the SoC boots
fine with and all 4 cores work.

Hmm... where does it hang? Can you tell if it's the access to the GCR
registers causing the hang or some subsequent access?

Post by John Crispin
The MT7621 has a broken iocu so i guess this might be related ? could someone that
actually knows what those registers do enlighten me please :)

Adding Paul who probably knows more.

Do you know what the initial values of the GCR_REGn_{BASE,MASK}
registers are? Perhaps they're initially enabled and by writing the
base address first we screw up some translation? It looks like just
writing 0 to the mask register should also disable the region, at
least according to the interAptiv manual I have.