[PATCH 1/2] arm: mvebu: a38x: serdes: fix serdes config for USB3

Stefan Eichenberger eichest at gmail.com
Thu Dec 9 11:19:33 CET 2021

The electrical serdes configuration for USB3 expects an array as data
argument. For USB3 the second value is used (see data_arr_idx = USB3 =
1). However, because only one value is inside the array mv_seq_exec is
accessing an invalid element and the serdes is configured wrongly.

This wrong initialization is leading to an unreliable detection
mechanism for some USB3 devices. We were able to reproduce the issue
regularly with an LTE modem from Sierra Wireless (SM7455) where it was
not detected as USB3 device in 1/3 of all tests.

This commit fixes the issue by setting data_arr_idx to 0. This is the
same value as the original U-Boot from Marvell is using. There it is
called FIRST_CELL which is a define for 0.
See: https://github.com/MarvellEmbeddedProcessors/u-boot-marvell
commit 56f963ce4c ("fix: serdes: a38x, a39x: Fix USB3 serdes DB

Signed-off-by: Stefan Eichenberger <eichest at gmail.com>
Signed-off-by: René Straub <rene.straub at netmodule.com>
 arch/arm/mach-mvebu/serdes/a38x/high_speed_env_spec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/mach-mvebu/serdes/a38x/high_speed_env_spec.c b/arch/arm/mach-mvebu/serdes/a38x/high_speed_env_spec.c
index d2bc3ab25c..11b5824232 100644
--- a/arch/arm/mach-mvebu/serdes/a38x/high_speed_env_spec.c
+++ b/arch/arm/mach-mvebu/serdes/a38x/high_speed_env_spec.c
@@ -1204,7 +1204,7 @@ int hws_serdes_seq_db_init(void)
 		    sizeof(usb3_electrical_config_serdes_rev2_params) /
 		    sizeof(struct op_params);
-	serdes_seq_db[USB3_ELECTRICAL_CONFIG_SEQ].data_arr_idx = USB3;
+	serdes_seq_db[USB3_ELECTRICAL_CONFIG_SEQ].data_arr_idx = 0;
 	/* USB3_TX_CONFIG_SEQ sequence init */
 	serdes_seq_db[USB3_TX_CONFIG_SEQ1].op_params_ptr =

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