New patch to review for coreboot: c2ccc1c chromeec: Add wakeup delay after SPI /CS assertion

[Stefan Reinauer]

Stefan Reinauer ([e-mail]) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/9217

-gerrit

commit c2ccc1ca2ac904ae31b79f73b303886fc98aae09
Author: David Hendricks 
Date:   Sat Sep 27 20:04:49 2014 -0700

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 
    Original-Commit-Id: ec6b10e4e3f0362dea0dc8046cfd4e4615a42585
    Original-Change-Id: Ibba356e4af18f80a7da73c96dadfda0f25251381
    Original-Signed-off-by: David Hendricks 
    Original-Reviewed-on: https://chromium-review.googlesource.com/220242
    Original-Reviewed-by: Julius Werner 
    Original-Reviewed-by: Alexandru Stan 
---
 src/ec/google/chromeec/Kconfig  | 7 +++++++
 src/ec/google/chromeec/ec_spi.c | 5 +++++
 2 files changed, 12 insertions(+)

diff --git a/src/ec/google/chromeec/Kconfig b/src/ec/google/chromeec/Kconfig
index bec12fb..32a4213 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 4b3e587..d11348c 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);