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authorDavid Hendricks <dhendrix@chromium.org>2014-09-27 20:04:49 -0700
committerPatrick Georgi <pgeorgi@google.com>2015-04-02 17:28:14 +0200
commit767d245ebf2d6d797bf759d23778553ed6f2a0b2 (patch)
tree247940814ab4844978218296b1e81409d9798d74
parent842978631580333becf635cc78f1901615d34929 (diff)
chromeec: Add wakeup delay after SPI /CS assertion
Some ECs may require a few microseconds to ramp up their clock after being awaken by /CS assertion. This adds a Kconfig variable that can be overridden at the mainboard-level which will force a delay between asserting /CS and beginning a transfer. BUG=chrome-os-partner:32223 BRANCH=none TEST=verified ~100us delay using logic analyzer Change-Id: I6d9b8beaa808252f008efb10e7448afdf96d2004 Signed-off-by: Stefan Reinauer <reinauer@chromium.org> Original-Commit-Id: ec6b10e4e3f0362dea0dc8046cfd4e4615a42585 Original-Change-Id: Ibba356e4af18f80a7da73c96dadfda0f25251381 Original-Signed-off-by: David Hendricks <dhendrix@chromium.org> Original-Reviewed-on: https://chromium-review.googlesource.com/220242 Original-Reviewed-by: Julius Werner <jwerner@chromium.org> Original-Reviewed-by: Alexandru Stan <amstan@chromium.org> Reviewed-on: http://review.coreboot.org/9217 Reviewed-by: David Hendricks <dhendrix@chromium.org> Tested-by: build bot (Jenkins)
-rw-r--r--src/ec/google/chromeec/Kconfig7
-rw-r--r--src/ec/google/chromeec/ec_spi.c5
2 files changed, 12 insertions, 0 deletions
diff --git a/src/ec/google/chromeec/Kconfig b/src/ec/google/chromeec/Kconfig
index bec12fb10a..32a42133f2 100644
--- a/src/ec/google/chromeec/Kconfig
+++ b/src/ec/google/chromeec/Kconfig
@@ -43,6 +43,13 @@ config EC_GOOGLE_CHROMEEC_SPI_BUS
depends on EC_GOOGLE_CHROMEEC_SPI
hex "SPI bus for Google's Chrome EC"
+config EC_GOOGLE_CHROMEEC_SPI_WAKEUP_DELAY_US
+ depends on EC_GOOGLE_CHROMEEC_SPI
+ int
+ default 0
+ help
+ Force delay after asserting /CS to allow EC to wakeup.
+
config EC_GOOGLE_CHROMEEC_SPI_CHIP
depends on EC_GOOGLE_CHROMEEC_SPI
hex
diff --git a/src/ec/google/chromeec/ec_spi.c b/src/ec/google/chromeec/ec_spi.c
index 4b3e587266..d11348cff7 100644
--- a/src/ec/google/chromeec/ec_spi.c
+++ b/src/ec/google/chromeec/ec_spi.c
@@ -18,6 +18,7 @@
*/
#include <console/console.h>
+#include <delay.h>
#include "ec.h"
#include "ec_commands.h"
#include <spi-generic.h>
@@ -50,6 +51,10 @@ static int crosec_spi_io(size_t req_size, size_t resp_size, void *context)
spi_claim_bus(slave);
+ /* Allow EC to ramp up clock after being awaken.
+ * See chrome-os-partner:32223 for more details. */
+ udelay(CONFIG_EC_GOOGLE_CHROMEEC_SPI_WAKEUP_DELAY_US);
+
if (spi_xfer(slave, req_buf, req_size, NULL, 0)) {
printk(BIOS_ERR, "%s: Failed to send request.\n", __func__);
spi_release_bus(slave);