[coreboot-gerrit] New patch to review for coreboot: ec/google/chromeec: Add minimum delay between SPI CS assertions

[Patrick Georgi]

Patrick Georgi ([e-mail]) just uploaded a new patch set to gerrit, which you can find at https://review.coreboot.org/16885

-gerrit

commit 65692da37ff59603a2b679fc4137486a6c0a14a8
Author: Julius Werner 
Date:   Mon Oct 3 12:52:55 2016 -0700

ec/google/chromeec: Add minimum delay between SPI CS assertions

Some Chrome OS ECs require a small amount of time after a SPI
    transaction to reset their controllers before they can service the next
    CS assertion. The kernel and depthcharge have always enforced a 200us
    minimum delay for this... coreboot should've done the same.

BRANCH=gru
    BUG=chrome-os-partner:58046
    TEST=Booted Kevin in recovery mode, confirmed that recovery events got
    logged with correct timestamps in eventlog.

Change-Id: I32ec343f3293ac93729d3e6e2f43d7605a396cdb
    Signed-off-by: Patrick Georgi 
    Original-Commit-Id: b9e4696533d4318ae7c8715b71ab963d8897c16c
    Original-Change-Id: I6a7baf7859d5d50e299495d118e7890dcaa2c1b0
    Original-Signed-off-by: Julius Werner 
    Original-Reviewed-on: https://chromium-review.googlesource.com/392206
    Original-Tested-by: Shawn N 
    Original-Reviewed-by: Shawn N 
---
 src/ec/google/chromeec/ec_spi.c | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/src/ec/google/chromeec/ec_spi.c b/src/ec/google/chromeec/ec_spi.c
index e93d038..a0049c6 100644
--- a/src/ec/google/chromeec/ec_spi.c
+++ b/src/ec/google/chromeec/ec_spi.c
@@ -20,6 +20,11 @@
 #include <spi-generic.h>
 #include <timer.h>

+/* This is assuming that this driver is not used on x86. If that changes, this
+   might need to become a CAR_GLOBAL or maybe even more complicated. */
+static struct stopwatch cs_cooldown_sw;
+static const long cs_cooldown_us = 200;
+
 static const uint8_t EcFramingByte = 0xec;

#define PROTO3_MAX_PACKET_SIZE 268
@@ -44,7 +49,10 @@ void *crosec_get_buffer(size_t size, int req)
 static int crosec_spi_io(size_t req_size, size_t resp_size, void *context)
 {
    struct spi_slave *slave = (struct spi_slave *)context;
+	int ret = 0;

+	while (!stopwatch_expired(&cs_cooldown_sw))
+		/* Wait minimum delay between CS assertions. */;
    spi_claim_bus(slave);

/* Allow EC to ramp up clock after being awaken.
@@ -53,8 +61,8 @@ static int crosec_spi_io(size_t req_size, size_t resp_size, void *context)

if (spi_xfer(slave, req_buf, req_size, NULL, 0)) {
    	printk(BIOS_ERR, "%s: Failed to send request.\n", __func__);
-		spi_release_bus(slave);
-		return -1;
+		ret = -1;
+		goto out;
    }

uint8_t byte;
@@ -65,8 +73,8 @@ static int crosec_spi_io(size_t req_size, size_t resp_size, void *context)
    	if (spi_xfer(slave, NULL, 0, &byte, sizeof(byte))) {
    		printk(BIOS_ERR, "%s: Failed to receive byte.\n",
    		       __func__);
-			spi_release_bus(slave);
-			return -1;
+			ret = -1;
+			goto out;
    	}
    	if (byte == EcFramingByte)
    		break;
@@ -75,28 +83,30 @@ static int crosec_spi_io(size_t req_size, size_t resp_size, void *context)
    		printk(BIOS_ERR,
    		       "%s: Timeout waiting for framing byte.\n",
    		       __func__);
-			spi_release_bus(slave);
-			return -1;
+			ret = -1;
+			goto out;
    	}
    }

if (spi_xfer(slave, NULL, 0, resp_buf, resp_size)) {
    	printk(BIOS_ERR, "%s: Failed to receive response.\n", __func__);
-		spi_release_bus(slave);
-		return -1;
+		ret = -1;
    }

+out:
    spi_release_bus(slave);
-
-	return 0;
+	stopwatch_init_usecs_expire(&cs_cooldown_sw, cs_cooldown_us);
+	return ret;
 }

int google_chromeec_command(struct chromeec_command *cec_command)
 {
    static struct spi_slave *slave = NULL;
-	if (!slave)
+	if (!slave) {
    	slave = spi_setup_slave(CONFIG_EC_GOOGLE_CHROMEEC_SPI_BUS,
    				CONFIG_EC_GOOGLE_CHROMEEC_SPI_CHIP);
+		stopwatch_init(&cs_cooldown_sw);
+	}
    return crosec_command_proto(cec_command, crosec_spi_io, slave);
 }