am33xx-restart.c

 1// SPDX-License-Identifier: GPL-2.0-only
 2/*
 3 * am33xx-restart.c - Code common to all AM33xx machines.
 4 */
 5#include <dt-bindings/pinctrl/am33xx.h>
 6#include <linux/delay.h>
 7#include <linux/kernel.h>
 8#include <linux/reboot.h>
 9
10#include "common.h"
11#include "control.h"
12#include "prm.h"
13
14/*
15 * Advisory 1.0.36 EMU0 and EMU1: Terminals Must be Pulled High Before
16 * ICEPick Samples
17 *
18 * If EMU0/EMU1 pins have been used as GPIO outputs and actively driving low
19 * level, the device might not reboot in normal mode. We are in a bad position
20 * to override GPIO state here, so just switch the pins into EMU input mode
21 * (that's what reset will do anyway) and wait a bit, because the state will be
22 * latched 190 ns after reset.
23 */
24static void am33xx_advisory_1_0_36(void)
25{
26	u32 emu0 = omap_ctrl_readl(AM335X_PIN_EMU0);
27	u32 emu1 = omap_ctrl_readl(AM335X_PIN_EMU1);
28
29	/* If both pins are in EMU mode, nothing to do */
30	if (!(emu0 & 7) && !(emu1 & 7))
31		return;
32
33	/* Switch GPIO3_7/GPIO3_8 into EMU0/EMU1 modes respectively */
34	omap_ctrl_writel(emu0 & ~7, AM335X_PIN_EMU0);
35	omap_ctrl_writel(emu1 & ~7, AM335X_PIN_EMU1);
36
37	/*
38	 * Give pull-ups time to load the pin/PCB trace capacity.
39	 * 5 ms shall be enough to load 1 uF (would be huge capacity for these
40	 * pins) with TI-recommended 4k7 external pull-ups.
41	 */
42	mdelay(5);
43}
44
45/**
46 * am33xx_restart - trigger a software restart of the SoC
47 * @mode: the "reboot mode", see arch/arm/kernel/{setup,process}.c
48 * @cmd: passed from the userspace program rebooting the system (if provided)
49 *
50 * Resets the SoC.  For @cmd, see the 'reboot' syscall in
51 * kernel/sys.c.  No return value.
52 */
53void am33xx_restart(enum reboot_mode mode, const char *cmd)
54{
55	am33xx_advisory_1_0_36();
56
57	/* TODO: Handle cmd if necessary */
58	prm_reboot_mode = mode;
59
60	omap_prm_reset_system();
61}