diff options
Diffstat (limited to 'chip/g/jitter.c')
| -rw-r--r-- | chip/g/jitter.c | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/chip/g/jitter.c b/chip/g/jitter.c new file mode 100644 index 0000000000..db1859b0d4 --- /dev/null +++ b/chip/g/jitter.c @@ -0,0 +1,51 @@ +/* Copyright 2016 The Chromium OS Authors. All rights reserved. + * Use of this source code is governed by a BSD-style license that can be + * found in the LICENSE file. + */ + +#include "common.h" +#include "console.h" +#include "init_chip.h" +#include "registers.h" + +void init_jittery_clock(int highsec) +{ + unsigned trimfast = GR_FUSE(RC_JTR_OSC60_CC_TRIM); + unsigned trim48 = GR_FUSE(RC_JTR_OSC48_CC_TRIM); + unsigned delta = (trim48 - trimfast); + /* for metastability reasons, avoid clk_jtr ~= clk_timer, make + * a keepout region around 24MHz of about 0.75MHz, about 3/16 of the + * the delta from trimfast and trim48 */ + unsigned skiplow = (trim48 << 4) - (delta * 6); + unsigned skiphigh = (trim48 << 4) + (delta * 6); + unsigned setting = trimfast << 4; + unsigned stepx16; + unsigned bankval; + int bank; + + if (highsec) + stepx16 = 0xff - trimfast; + else + stepx16 = 2 * (trim48 - trimfast); + + for (bank = 0; bank < 16; bank++) { + /* saturate at 0xff */ + bankval = (setting > 0xfff) ? 0xff : (setting >> 4); + + GR_XO_JTR_JITTERY_TRIM_BANK(bank) = bankval; + + setting += stepx16; + if ((setting > skiplow) && (setting < skiphigh)) + setting = skiphigh; + } + + GWRITE_FIELD(XO, CLK_JTR_TRIM_CTRL, RC_COARSE_TRIM_SRC, 2); + GWRITE_FIELD(XO, CLK_JTR_TRIM_CTRL, RC_INITIAL_TRIM_PERIOD, 100); + GWRITE_FIELD(XO, CLK_JTR_TRIM_CTRL, RC_TRIM_EN, 1); + GREG32(XO, CLK_JTR_JITTERY_TRIM_EN) = 1; + GREG32(XO, CLK_JTR_SYNC_CONTENTS) = 0; + + /* Writing any value locks things until the next hard reboot */ + GREG32(XO, CFG_WR_EN) = 0; + GREG32(XO, JTR_CTRL_EN) = 0; +} |