ipq8064: Add work around for slow timer clock

Libpayload libc requires timer clock frequency to be at least 1MHz.
Ipq8064 code presently provides a single option of 32kHz. Pretend to
be running at 1 MHz without additional accuracy.

This is a hack which will be reverted as soon as the SOC is configured
to supply a faster running clock.

BUG=chrome-os-partner:27784, chrome-os-partner:28880
TEST=with other changes depthcharge boots to the CLI console

Original-Change-Id: I80ec6652bc5693a549668cd6e824e9cf5c26b182
Original-Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/201342
Original-Reviewed-by: David Hendricks <dhendrix@chromium.org>
(cherry picked from commit 466a59967b13986099106f8b44924648c1e6e6cd)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: I113689191db70710e7a45ccd02d672f482343e35
Reviewed-on: http://review.coreboot.org/8004
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Tested-by: build bot (Jenkins)

1 files changed, 20 insertions, 2 deletions

diff --git a/payloads/libpayload/drivers/timer/ipq806x.c b/payloads/libpayload/drivers/timer/ipq806x.c
index 4edbf8eda0..0d70a86813 100644
--- a/payloads/libpayload/drivers/timer/ipq806x.c
+++ b/payloads/libpayload/drivers/timer/ipq806x.c
@@ -29,13 +29,31 @@
 
 #include <libpayload.h>
 
+/*
+ * TODO(vbendeb): reverted this hack once proper timer code is in place (see
+ * http://crosbug.com/p/28880 for details.
+ */
+#define MIN_TIMER_FREQ 1000000
+
 uint64_t timer_hz(void)
 {
-	return CONFIG_LP_IPQ806X_TIMER_FREQ;
+	return (CONFIG_LP_IPQ806X_TIMER_FREQ >= MIN_TIMER_FREQ) ?
+		CONFIG_LP_IPQ806X_TIMER_FREQ : MIN_TIMER_FREQ;
 }
 
 uint64_t timer_raw_value(void)
 {
-	return readl((void *)CONFIG_LP_IPQ806X_TIMER_REG);
+	uint64_t rawv = readl((void *)CONFIG_LP_IPQ806X_TIMER_REG);
+
+	/*
+	 * This is extremely crude, but it kicks in only for the case when the
+	 * timer clock frequency is below 1MHz, which should never be the case
+	 * on a properly configured system. The compiler will eliminate the
+	 * check as long as config value exceeds 1MHz.
+	 */
+	if (CONFIG_LP_IPQ806X_TIMER_FREQ < MIN_TIMER_FREQ)
+		rawv *= (MIN_TIMER_FREQ / CONFIG_LP_IPQ806X_TIMER_FREQ);
+
+	return rawv;
 }