edi: Add dummy read to ensure proper detection of ENE chips

ENE chips enable EDI by detecting a clock frequency between 1 MHz and 8 MHz.
In many cases, the chip won't be able to both detect the clock signal and
serve the associated request at the same time.

Thus, a dummy read has to be added to ensure that EDI is enabled and
operational starting from the next request.

Change-Id: I69ee71674649cd8ba4fc635f889cb39a1cd204b9
Signed-off-by: Mike Banon <mikebdp2@gmail.com>
Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
Reviewed-on: https://review.coreboot.org/23260
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/edi.c b/edi.c
index 0ca170428..9397a54eb 100644
--- a/edi.c
+++ b/edi.c
@@ -480,6 +480,18 @@ int edi_probe_kb9012(struct flashctx *flash)
 {
 	int probe;
 	int rc;
+	unsigned char hwversion;
+
+	/*
+	 * ENE chips enable EDI by detecting a clock frequency between 1 MHz and
+	 * 8 MHz. In many cases, the chip won't be able to both detect the clock
+	 * signal and serve the associated request at the same time.
+	 *
+	 * Thus, a dummy read has to be added to ensure that EDI is enabled and
+	 * operational starting from the next request. This dummy read below
+	 * draws the chip's attention and as result the chip enables its EDI.
+	 */
+	edi_read(flash, ENE_EC_HWVERSION, &hwversion);
 
 	probe = edi_chip_probe(flash, &ene_kb9012);
 	if (!probe)