[PATCH u-boot-marvell] ddr: marvell: a38x: fix BYTE_HOMOGENEOUS_SPLIT_OUT decision

Marek Behún kabel at kernel.org
Thu Feb 17 01:08:37 CET 2022

From: Marek Behún <marek.behun at nic.cz>

In commit 3fc92a215b69 ("ddr: marvell: a38x: fix SPLIT_OUT_MIX state
decision") I ported a cleaned up and changed version of patch
  mv_ddr: a380: fix SPLIT_OUT_MIX state decision

In the port we removed checking for BYTE_HOMOGENEOUS_SPLIT_OUT bit,
- the fix seemed to work without it
- the bit was checked for only at one place out of two, while the second
  bit, BYTE_SPLIT_OUT_MIX, was checked for in both cases
- without the removal it didn't work on Allied Telesis' x530 board

We recently had a chance to test on more boards, and it seems that the
change needs to be opposite: instead of removing the check for
BYTE_HOMOGENEOUS_SPLIT_OUT from the first if() statement, the check
needs to be added also to the second one - it needs to be at both

With this change all the Turris Omnia boards I have had available to
test seem to work, I didn't encounter not even one failed DDR training.

As last time, I am noting that I do not understand what this code is
actually doing, I haven't studied the DDR training algorithm and
I suspect that no one will be able to explain it to U-Boot contributors,
so we are left with this blind poking in the code with testing whether
it works on several boards and hoping it doesn't break anything for
anyone :-(.

Signed-off-by: Marek Behún <marek.behun at nic.cz>
Tested-by: Chris Packham <judge.packham at gmail.com>
Reviewed-by: Stefan Roese <sr at denx.de>
 drivers/ddr/marvell/a38x/ddr3_training_centralization.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/ddr/marvell/a38x/ddr3_training_centralization.c b/drivers/ddr/marvell/a38x/ddr3_training_centralization.c
index 42308b6965..be9f985f22 100644
--- a/drivers/ddr/marvell/a38x/ddr3_training_centralization.c
+++ b/drivers/ddr/marvell/a38x/ddr3_training_centralization.c
@@ -180,7 +180,8 @@ static int ddr3_tip_centralization(u32 dev_num, u32 mode)
 					if (current_byte_status &
-					    BYTE_SPLIT_OUT_MIX) {
+					    (BYTE_SPLIT_OUT_MIX |
 						if (cur_start_win[bit_id] >= 64)
 							cur_start_win[bit_id] -= 64;
@@ -197,7 +198,8 @@ static int ddr3_tip_centralization(u32 dev_num, u32 mode)
 					if (cur_end_win[bit_id] >= 64 &&
 					    (current_byte_status &
-					     BYTE_SPLIT_OUT_MIX)) {
+					     (BYTE_SPLIT_OUT_MIX |
 						cur_end_win[bit_id] -= 64;

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