tegra124: More improvements to the clock initialization macros.

Consolidate the register setting clrsetbits_le32 call to simplify the macros.
Add a check for bits of the divisor being dropped. The clock source registers
will throw away bits that aren't supported, so we can check for divisor
overflow by checking for dropped bits.

BUG=None
TEST=Purposefully tried to set a clock to a rate which overflows its divisor.
Verified that the check triggered. Booted on nyan. Verified the TPM i2c bus
frequency was still correct.
BRANCH=None

Original-Change-Id: I3b1b6ba57f6b7729f303d15a16b685a48751d41f
Original-Signed-off-by: Gabe Black <gabeblack@google.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/193348
Original-Reviewed-by: Gabe Black <gabeblack@chromium.org>
Original-Commit-Queue: Gabe Black <gabeblack@chromium.org>
Original-Tested-by: Gabe Black <gabeblack@chromium.org>
(cherry picked from commit 9cd79dd974d8a3c31398f8fbd62750b194867891)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: Id4d8ecfeff52737cdd68999028b37cbdedb0d116
Reviewed-on: http://review.coreboot.org/7738
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

1 files changed, 23 insertions, 9 deletions

diff --git a/src/soc/nvidia/tegra124/include/soc/clock.h b/src/soc/nvidia/tegra124/include/soc/clock.h
index 7038b87b7e16..10cf2d8679df 100644
--- a/src/soc/nvidia/tegra124/include/soc/clock.h
+++ b/src/soc/nvidia/tegra124/include/soc/clock.h
@@ -18,6 +18,10 @@
 #ifndef __SOC_NVIDIA_TEGRA124_CLOCK_H__
 #define __SOC_NVIDIA_TEGRA124_CLOCK_H__
 
+#include <arch/hlt.h>
+#include <arch/io.h>
+#include <console/console.h>
+#include <soc/nvidia/tegra124/clk_rst.h>
 #include <stdint.h>
 #include <stdlib.h>
 
@@ -218,11 +222,23 @@ enum {
  */
 #define CLK_FREQUENCY(REF, REG)	(((REF) * 2) / ((REG) + 2))
 
+static inline void _clock_set_div(u32 *reg, const char *name, u32 div,
+				  u32 div_mask, u32 src)
+{
+	// The I2C and UART divisors are 16 bit while all the others are 8 bit.
+	// The I2C clocks are handled by the specialized macro below, but the
+	// UART clocks aren't. Don't use this function on UART clocks.
+	if (div & ~div_mask) {
+		printk(BIOS_ERR, "%s clock divisor overflow!", name);
+		hlt();
+	}
+	clrsetbits_le32(reg, CLK_SOURCE_MASK | CLK_DIVISOR_MASK,
+			src << CLK_SOURCE_SHIFT | div);
+}
+
 #define clock_configure_irregular_source(device, src, freq, src_id) \
-	clrsetbits_le32(&clk_rst->clk_src_##device, \
-		CLK_SOURCE_MASK | CLK_DIVISOR_MASK, \
-		src_id << CLK_SOURCE_SHIFT | \
-		CLK_DIVIDER(TEGRA_##src##_KHZ, freq))
+	_clock_set_div(&clk_rst->clk_src_##device, #device, \
+		CLK_DIVIDER(TEGRA_##src##_KHZ, freq), 0xff, src_id)
 
 /* Warning: Some devices just use different bits for the same sources for no
  * apparent reason. *Always* double-check the TRM before trusting this macro. */
@@ -237,11 +253,9 @@ enum {
  * documentation.
  */
 #define clock_configure_i2c_scl_freq(device, src, freq) \
-	clrsetbits_le32(&clk_rst->clk_src_##device, \
-		CLK_SOURCE_MASK | CLK_DIVISOR_MASK, \
-		src << CLK_SOURCE_SHIFT | \
-		(div_round_up((TEGRA_##src##_KHZ), \
-			      ((freq) * (0x19 + 1) * 8)) - 1))
+	_clock_set_div(&clk_rst->clk_src_##device, #device, \
+		div_round_up(TEGRA_##src##_KHZ, (freq) * (0x19 + 1) * 8) - 1, \
+		0xffff, src)
 
 enum clock_source {  /* Careful: Not true for all sources, always check TRM! */
 	PLLP = 0,