linux-imx

/*

 * CPU frequency scaling for Broadcom SoCs with AVS firmware that

 * supports DVS or DVFS

 *

 * Copyright (c) 2016 Broadcom

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of the GNU General Public License as

 * published by the Free Software Foundation version 2.

 *

 * This program is distributed "as is" WITHOUT ANY WARRANTY of any

 * kind, whether express or implied; without even the implied warranty

 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 */

​

/*

 * "AVS" is the name of a firmware developed at Broadcom. It derives

 * its name from the technique called "Adaptive Voltage Scaling".

 * Adaptive voltage scaling was the original purpose of this firmware.

 * The AVS firmware still supports "AVS mode", where all it does is

 * adaptive voltage scaling. However, on some newer Broadcom SoCs, the

 * AVS Firmware, despite its unchanged name, also supports DFS mode and

 * DVFS mode.

 *

 * In the context of this document and the related driver, "AVS" by

 * itself always means the Broadcom firmware and never refers to the

 * technique called "Adaptive Voltage Scaling".

 *

 * The Broadcom STB AVS CPUfreq driver provides voltage and frequency

 * scaling on Broadcom SoCs using AVS firmware with support for DFS and

 * DVFS. The AVS firmware is running on its own co-processor. The

 * driver supports both uniprocessor (UP) and symmetric multiprocessor

 * (SMP) systems which share clock and voltage across all CPUs.

 *

 * Actual voltage and frequency scaling is done solely by the AVS

 * firmware. This driver does not change frequency or voltage itself.

 * It provides a standard CPUfreq interface to the rest of the kernel

 * and to userland. It interfaces with the AVS firmware to effect the

 * requested changes and to report back the current system status in a

 * way that is expected by existing tools.

 */

​

#include <linux/cpufreq.h>

#include <linux/interrupt.h>

#include <linux/io.h>

#include <linux/module.h>

#include <linux/of_address.h>

#include <linux/platform_device.h>

#include <linux/semaphore.h>

​

/* Max number of arguments AVS calls take */

#define AVS_MAX_CMD_ARGS    4

/*

 * This macro is used to generate AVS parameter register offsets. For

 * x >= AVS_MAX_CMD_ARGS, it returns 0 to protect against accidental memory

 * access outside of the parameter range. (Offset 0 is the first parameter.)

 */

#define AVS_PARAM_MULT(x)   ((x) < AVS_MAX_CMD_ARGS ? (x) : 0)

​

/* AVS Mailbox Register offsets */

#define AVS_MBOX_COMMAND    0x00

#define AVS_MBOX_STATUS     0x04