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// SPDX-License-Identifier: GPL-2.0+
/*
* Power domain driver for Broadcom BCM2835
*
* Copyright (C) 2018 Broadcom
*/
#include <dt-bindings/soc/bcm2835-pm.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/mfd/bcm2835-pm.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/pm_domain.h>
#include <linux/reset-controller.h>
#include <linux/types.h>
#define PM_GNRIC 0x00
#define PM_AUDIO 0x04
#define PM_STATUS 0x18
#define PM_RSTC 0x1c
#define PM_RSTS 0x20
#define PM_WDOG 0x24
#define PM_PADS0 0x28
#define PM_PADS2 0x2c
#define PM_PADS3 0x30
#define PM_PADS4 0x34
#define PM_PADS5 0x38
#define PM_PADS6 0x3c
#define PM_CAM0 0x44
#define PM_CAM0_LDOHPEN BIT(2)
#define PM_CAM0_LDOLPEN BIT(1)
#define PM_CAM0_CTRLEN BIT(0)
#define PM_CAM1 0x48
#define PM_CAM1_LDOHPEN BIT(2)
#define PM_CAM1_LDOLPEN BIT(1)
#define PM_CAM1_CTRLEN BIT(0)
#define PM_CCP2TX 0x4c
#define PM_CCP2TX_LDOEN BIT(1)
#define PM_CCP2TX_CTRLEN BIT(0)
#define PM_DSI0 0x50
#define PM_DSI0_LDOHPEN BIT(2)
#define PM_DSI0_LDOLPEN BIT(1)
#define PM_DSI0_CTRLEN BIT(0)
#define PM_DSI1 0x54
#define PM_DSI1_LDOHPEN BIT(2)
#define PM_DSI1_LDOLPEN BIT(1)
#define PM_DSI1_CTRLEN BIT(0)
#define PM_HDMI 0x58
#define PM_HDMI_RSTDR BIT(19)
#define PM_HDMI_LDOPD BIT(1)
#define PM_HDMI_CTRLEN BIT(0)
#define PM_USB 0x5c
/* The power gates must be enabled with this bit before enabling the LDO in the
* USB block.
*/
#define PM_USB_CTRLEN BIT(0)
#define PM_PXLDO 0x60
#define PM_PXBG 0x64
#define PM_DFT 0x68
#define PM_SMPS 0x6c
#define PM_XOSC 0x70
#define PM_SPAREW 0x74
#define PM_SPARER 0x78
#define PM_AVS_RSTDR 0x7c
#define PM_AVS_STAT 0x80
#define PM_AVS_EVENT 0x84
#define PM_AVS_INTEN 0x88
#define PM_DUMMY 0xfc
#define PM_IMAGE 0x108
#define PM_GRAFX 0x10c
#define PM_PROC 0x110
#define PM_ENAB BIT(12)
#define PM_ISPRSTN BIT(8)
#define PM_H264RSTN BIT(7)
#define PM_PERIRSTN BIT(6)
#define PM_V3DRSTN BIT(6)
#define PM_ISFUNC BIT(5)
#define PM_MRDONE BIT(4)
#define PM_MEMREP BIT(3)
#define PM_ISPOW BIT(2)
#define PM_POWOK BIT(1)
#define PM_POWUP BIT(0)
#define PM_INRUSH_SHIFT 13
#define PM_INRUSH_3_5_MA 0
#define PM_INRUSH_5_MA 1
#define PM_INRUSH_10_MA 2
#define PM_INRUSH_20_MA 3
#define PM_INRUSH_MASK (3 << PM_INRUSH_SHIFT)
#define PM_PASSWORD 0x5a000000
#define PM_WDOG_TIME_SET 0x000fffff
#define PM_RSTC_WRCFG_CLR 0xffffffcf
#define PM_RSTS_HADWRH_SET 0x00000040
#define PM_RSTC_WRCFG_SET 0x00000030
#define PM_RSTC_WRCFG_FULL_RESET 0x00000020
#define PM_RSTC_RESET 0x00000102
#define PM_READ(reg) readl(power->base + (reg))
#define PM_WRITE(reg, val) writel(PM_PASSWORD | (val), power->base + (reg))
#define ASB_BRDG_VERSION 0x00
#define ASB_CPR_CTRL 0x04
#define ASB_V3D_S_CTRL 0x08
#define ASB_V3D_M_CTRL 0x0c
#define ASB_ISP_S_CTRL 0x10
#define ASB_ISP_M_CTRL 0x14
#define ASB_H264_S_CTRL 0x18
#define ASB_H264_M_CTRL 0x1c
#define ASB_REQ_STOP BIT(0)
#define ASB_ACK BIT(1)
#define ASB_EMPTY BIT(2)
#define ASB_FULL BIT(3)
#define ASB_AXI_BRDG_ID 0x20
#define BCM2835_BRDG_ID 0x62726467
struct bcm2835_power_domain {
struct generic_pm_domain base;
struct bcm2835_power *power;
u32 domain;
struct clk *clk;
};
struct bcm2835_power {
struct device *dev;
/* PM registers. */
void __iomem *base;
/* AXI Async bridge registers. */
void __iomem *asb;
/* RPiVid bridge registers. */
void __iomem *rpivid_asb;
struct genpd_onecell_data pd_xlate;
struct bcm2835_power_domain domains[BCM2835_POWER_DOMAIN_COUNT];
struct reset_controller_dev reset;
};
static int bcm2835_asb_control(struct bcm2835_power *power, u32 reg, bool enable)
{
void __iomem *base = power->asb;
u64 start;
u32 val;
switch (reg) {
case 0:
return 0;
case ASB_V3D_S_CTRL:
case ASB_V3D_M_CTRL:
if (power->rpivid_asb)
base = power->rpivid_asb;
break;
}
start = ktime_get_ns();
/* Enable the module's async AXI bridges. */
if (enable) {
val = readl(base + reg) & ~ASB_REQ_STOP;
} else {
val = readl(base + reg) | ASB_REQ_STOP;
}
writel(PM_PASSWORD | val, base + reg);
while (!!(readl(base + reg) & ASB_ACK) == enable) {
cpu_relax();
if (ktime_get_ns() - start >= 1000)
return -ETIMEDOUT;
}
return 0;
}
static int bcm2835_asb_enable(struct bcm2835_power *power, u32 reg)
{
return bcm2835_asb_control(power, reg, true);
}
static int bcm2835_asb_disable(struct bcm2835_power *power, u32 reg)
{
return bcm2835_asb_control(power, reg, false);
}
static int bcm2835_power_power_off(struct bcm2835_power_domain *pd, u32 pm_reg)
{
struct bcm2835_power *power = pd->power;
/* We don't run this on BCM2711 */
if (power->rpivid_asb)
return 0;
/* Enable functional isolation */
PM_WRITE(pm_reg, PM_READ(pm_reg) & ~PM_ISFUNC);
/* Enable electrical isolation */
PM_WRITE(pm_reg, PM_READ(pm_reg) & ~PM_ISPOW);
/* Open the power switches. */
PM_WRITE(pm_reg, PM_READ(pm_reg) & ~PM_POWUP);
return 0;
}
static int bcm2835_power_power_on(struct bcm2835_power_domain *pd, u32 pm_reg)
{
struct bcm2835_power *power = pd->power;
struct device *dev = power->dev;
u64 start;
int ret;
int inrush;
bool powok;
/* We don't run this on BCM2711 */
if (power->rpivid_asb)
return 0;
/* If it was already powered on by the fw, leave it that way. */
if (PM_READ(pm_reg) & PM_POWUP)
return 0;
/* Enable power. Allowing too much current at once may result
* in POWOK never getting set, so start low and ramp it up as
* necessary to succeed.
*/
powok = false;
for (inrush = PM_INRUSH_3_5_MA; inrush <= PM_INRUSH_20_MA; inrush++) {
PM_WRITE(pm_reg,
(PM_READ(pm_reg) & ~PM_INRUSH_MASK) |
(inrush << PM_INRUSH_SHIFT) |
PM_POWUP);
start = ktime_get_ns();
while (!(powok = !!(PM_READ(pm_reg) & PM_POWOK))) {
cpu_relax();
if (ktime_get_ns() - start >= 3000)
break;
}
}
if (!powok) {
dev_err(dev, "Timeout waiting for %s power OK\n",
pd->base.name);
ret = -ETIMEDOUT;
goto err_disable_powup;
}
/* Disable electrical isolation */
PM_WRITE(pm_reg, PM_READ(pm_reg) | PM_ISPOW);
/* Repair memory */
PM_WRITE(pm_reg, PM_READ(pm_reg) | PM_MEMREP);
start = ktime_get_ns();
while (!(PM_READ(pm_reg) & PM_MRDONE)) {
cpu_relax();
if (ktime_get_ns() - start >= 1000) {
dev_err(dev, "Timeout waiting for %s memory repair\n",
pd->base.name);
ret = -ETIMEDOUT;
goto err_disable_ispow;
}
}
/* Disable functional isolation */
PM_WRITE(pm_reg, PM_READ(pm_reg) | PM_ISFUNC);
return 0;
err_disable_ispow:
PM_WRITE(pm_reg, PM_READ(pm_reg) & ~PM_ISPOW);
err_disable_powup:
PM_WRITE(pm_reg, PM_READ(pm_reg) & ~(PM_POWUP | PM_INRUSH_MASK));
return ret;
}
static int bcm2835_asb_power_on(struct bcm2835_power_domain *pd,
u32 pm_reg,
u32 asb_m_reg,
u32 asb_s_reg,
u32 reset_flags)
{
struct bcm2835_power *power = pd->power;
int ret;
ret = clk_prepare_enable(pd->clk);
if (ret) {
dev_err(power->dev, "Failed to enable clock for %s\n",
pd->base.name);
return ret;
}
/* Wait 32 clocks for reset to propagate, 1 us will be enough */
udelay(1);
clk_disable_unprepare(pd->clk);
/* Deassert the resets. */
PM_WRITE(pm_reg, PM_READ(pm_reg) | reset_flags);
ret = clk_prepare_enable(pd->clk);
if (ret) {
dev_err(power->dev, "Failed to enable clock for %s\n",
pd->base.name);
goto err_enable_resets;
}
ret = bcm2835_asb_enable(power, asb_m_reg);
if (ret) {
dev_err(power->dev, "Failed to enable ASB master for %s\n",
pd->base.name);
goto err_disable_clk;
}
ret = bcm2835_asb_enable(power, asb_s_reg);
if (ret) {
dev_err(power->dev, "Failed to enable ASB slave for %s\n",
pd->base.name);
goto err_disable_asb_master;
}
return 0;
err_disable_asb_master:
bcm2835_asb_disable(power, asb_m_reg);
err_disable_clk:
clk_disable_unprepare(pd->clk);
err_enable_resets:
PM_WRITE(pm_reg, PM_READ(pm_reg) & ~reset_flags);
return ret;
}
static int bcm2835_asb_power_off(struct bcm2835_power_domain *pd,
u32 pm_reg,
u32 asb_m_reg,
u32 asb_s_reg,
u32 reset_flags)
{
struct bcm2835_power *power = pd->power;
int ret;
ret = bcm2835_asb_disable(power, asb_s_reg);
if (ret) {
dev_warn(power->dev, "Failed to disable ASB slave for %s\n",
pd->base.name);
return ret;
}
ret = bcm2835_asb_disable(power, asb_m_reg);
if (ret) {
dev_warn(power->dev, "Failed to disable ASB master for %s\n",
pd->base.name);
bcm2835_asb_enable(power, asb_s_reg);
return ret;
}
clk_disable_unprepare(pd->clk);
/* Assert the resets. */
PM_WRITE(pm_reg, PM_READ(pm_reg) & ~reset_flags);
return 0;
}
static int bcm2835_power_pd_power_on(struct generic_pm_domain *domain)
{
struct bcm2835_power_domain *pd =
container_of(domain, struct bcm2835_power_domain, base);
struct bcm2835_power *power = pd->power;
switch (pd->domain) {
case BCM2835_POWER_DOMAIN_GRAFX:
return bcm2835_power_power_on(pd, PM_GRAFX);
case BCM2835_POWER_DOMAIN_GRAFX_V3D:
return bcm2835_asb_power_on(pd, PM_GRAFX,
ASB_V3D_M_CTRL, ASB_V3D_S_CTRL,
PM_V3DRSTN);
case BCM2835_POWER_DOMAIN_IMAGE:
return bcm2835_power_power_on(pd, PM_IMAGE);
case BCM2835_POWER_DOMAIN_IMAGE_PERI:
return bcm2835_asb_power_on(pd, PM_IMAGE,
0, 0,
PM_PERIRSTN);
case BCM2835_POWER_DOMAIN_IMAGE_ISP:
return bcm2835_asb_power_on(pd, PM_IMAGE,
ASB_ISP_M_CTRL, ASB_ISP_S_CTRL,
PM_ISPRSTN);
case BCM2835_POWER_DOMAIN_IMAGE_H264:
return bcm2835_asb_power_on(pd, PM_IMAGE,
ASB_H264_M_CTRL, ASB_H264_S_CTRL,
PM_H264RSTN);
case BCM2835_POWER_DOMAIN_USB:
PM_WRITE(PM_USB, PM_USB_CTRLEN);
return 0;
case BCM2835_POWER_DOMAIN_DSI0:
PM_WRITE(PM_DSI0, PM_DSI0_CTRLEN);
PM_WRITE(PM_DSI0, PM_DSI0_CTRLEN | PM_DSI0_LDOHPEN);
return 0;
case BCM2835_POWER_DOMAIN_DSI1:
PM_WRITE(PM_DSI1, PM_DSI1_CTRLEN);
PM_WRITE(PM_DSI1, PM_DSI1_CTRLEN | PM_DSI1_LDOHPEN);
return 0;
case BCM2835_POWER_DOMAIN_CCP2TX:
PM_WRITE(PM_CCP2TX, PM_CCP2TX_CTRLEN);
PM_WRITE(PM_CCP2TX, PM_CCP2TX_CTRLEN | PM_CCP2TX_LDOEN);
return 0;
case BCM2835_POWER_DOMAIN_HDMI:
PM_WRITE(PM_HDMI, PM_READ(PM_HDMI) | PM_HDMI_RSTDR);
PM_WRITE(PM_HDMI, PM_READ(PM_HDMI) | PM_HDMI_CTRLEN);
PM_WRITE(PM_HDMI, PM_READ(PM_HDMI) & ~PM_HDMI_LDOPD);
usleep_range(100, 200);
PM_WRITE(PM_HDMI, PM_READ(PM_HDMI) & ~PM_HDMI_RSTDR);
return 0;
default:
dev_err(power->dev, "Invalid domain %d\n", pd->domain);
return -EINVAL;
}
}
static int bcm2835_power_pd_power_off(struct generic_pm_domain *domain)
{
struct bcm2835_power_domain *pd =
container_of(domain, struct bcm2835_power_domain, base);
struct bcm2835_power *power = pd->power;
switch (pd->domain) {
case BCM2835_POWER_DOMAIN_GRAFX:
return bcm2835_power_power_off(pd, PM_GRAFX);
case BCM2835_POWER_DOMAIN_GRAFX_V3D:
return bcm2835_asb_power_off(pd, PM_GRAFX,
ASB_V3D_M_CTRL, ASB_V3D_S_CTRL,
PM_V3DRSTN);
case BCM2835_POWER_DOMAIN_IMAGE:
return bcm2835_power_power_off(pd, PM_IMAGE);
case BCM2835_POWER_DOMAIN_IMAGE_PERI:
return bcm2835_asb_power_off(pd, PM_IMAGE,
0, 0,
PM_PERIRSTN);
case BCM2835_POWER_DOMAIN_IMAGE_ISP:
return bcm2835_asb_power_off(pd, PM_IMAGE,
ASB_ISP_M_CTRL, ASB_ISP_S_CTRL,
PM_ISPRSTN);
case BCM2835_POWER_DOMAIN_IMAGE_H264:
return bcm2835_asb_power_off(pd, PM_IMAGE,
ASB_H264_M_CTRL, ASB_H264_S_CTRL,
PM_H264RSTN);
case BCM2835_POWER_DOMAIN_USB:
PM_WRITE(PM_USB, 0);
return 0;
case BCM2835_POWER_DOMAIN_DSI0:
PM_WRITE(PM_DSI0, PM_DSI0_CTRLEN);
PM_WRITE(PM_DSI0, 0);
return 0;
case BCM2835_POWER_DOMAIN_DSI1:
PM_WRITE(PM_DSI1, PM_DSI1_CTRLEN);
PM_WRITE(PM_DSI1, 0);
return 0;
case BCM2835_POWER_DOMAIN_CCP2TX:
PM_WRITE(PM_CCP2TX, PM_CCP2TX_CTRLEN);
PM_WRITE(PM_CCP2TX, 0);
return 0;
case BCM2835_POWER_DOMAIN_HDMI:
PM_WRITE(PM_HDMI, PM_READ(PM_HDMI) | PM_HDMI_LDOPD);
PM_WRITE(PM_HDMI, PM_READ(PM_HDMI) & ~PM_HDMI_CTRLEN);
return 0;
default:
dev_err(power->dev, "Invalid domain %d\n", pd->domain);
return -EINVAL;
}
}
static int
bcm2835_init_power_domain(struct bcm2835_power *power,
int pd_xlate_index, const char *name)
{
struct device *dev = power->dev;
struct bcm2835_power_domain *dom = &power->domains[pd_xlate_index];
dom->clk = devm_clk_get(dev->parent, name);
if (IS_ERR(dom->clk)) {
int ret = PTR_ERR(dom->clk);
if (ret == -EPROBE_DEFER)
return ret;
/* Some domains don't have a clk, so make sure that we
* don't deref an error pointer later.
*/
dom->clk = NULL;
}
dom->base.name = name;
dom->base.power_on = bcm2835_power_pd_power_on;
dom->base.power_off = bcm2835_power_pd_power_off;
dom->domain = pd_xlate_index;
dom->power = power;
/* XXX: on/off at boot? */
pm_genpd_init(&dom->base, NULL, true);
power->pd_xlate.domains[pd_xlate_index] = &dom->base;
return 0;
}
/** bcm2835_reset_reset - Resets a block that has a reset line in the
* PM block.
*
* The consumer of the reset controller must have the power domain up
* -- there's no reset ability with the power domain down. To reset
* the sub-block, we just disable its access to memory through the
* ASB, reset, and re-enable.
*/
static int bcm2835_reset_reset(struct reset_controller_dev *rcdev,
unsigned long id)
{
struct bcm2835_power *power = container_of(rcdev, struct bcm2835_power,
reset);
struct bcm2835_power_domain *pd;
int ret;
switch (id) {
case BCM2835_RESET_V3D:
pd = &power->domains[BCM2835_POWER_DOMAIN_GRAFX_V3D];
break;
case BCM2835_RESET_H264:
pd = &power->domains[BCM2835_POWER_DOMAIN_IMAGE_H264];
break;
case BCM2835_RESET_ISP:
pd = &power->domains[BCM2835_POWER_DOMAIN_IMAGE_ISP];
break;
default:
dev_err(power->dev, "Bad reset id %ld\n", id);
return -EINVAL;
}
ret = bcm2835_power_pd_power_off(&pd->base);
if (ret)
return ret;
return bcm2835_power_pd_power_on(&pd->base);
}
static int bcm2835_reset_status(struct reset_controller_dev *rcdev,
unsigned long id)
{
struct bcm2835_power *power = container_of(rcdev, struct bcm2835_power,
reset);
switch (id) {
case BCM2835_RESET_V3D:
return !PM_READ(PM_GRAFX & PM_V3DRSTN);
case BCM2835_RESET_H264:
return !PM_READ(PM_IMAGE & PM_H264RSTN);
case BCM2835_RESET_ISP:
return !PM_READ(PM_IMAGE & PM_ISPRSTN);
default:
return -EINVAL;
}
}
static const struct reset_control_ops bcm2835_reset_ops = {
.reset = bcm2835_reset_reset,
.status = bcm2835_reset_status,
};
static const char *const power_domain_names[] = {
[BCM2835_POWER_DOMAIN_GRAFX] = "grafx",
[BCM2835_POWER_DOMAIN_GRAFX_V3D] = "v3d",
[BCM2835_POWER_DOMAIN_IMAGE] = "image",
[BCM2835_POWER_DOMAIN_IMAGE_PERI] = "peri_image",
[BCM2835_POWER_DOMAIN_IMAGE_H264] = "h264",
[BCM2835_POWER_DOMAIN_IMAGE_ISP] = "isp",
[BCM2835_POWER_DOMAIN_USB] = "usb",
[BCM2835_POWER_DOMAIN_DSI0] = "dsi0",
[BCM2835_POWER_DOMAIN_DSI1] = "dsi1",
[BCM2835_POWER_DOMAIN_CAM0] = "cam0",
[BCM2835_POWER_DOMAIN_CAM1] = "cam1",
[BCM2835_POWER_DOMAIN_CCP2TX] = "ccp2tx",
[BCM2835_POWER_DOMAIN_HDMI] = "hdmi",
};
static int bcm2835_power_probe(struct platform_device *pdev)
{
struct bcm2835_pm *pm = dev_get_drvdata(pdev->dev.parent);
struct device *dev = &pdev->dev;
struct bcm2835_power *power;
static const struct {
int parent, child;
} domain_deps[] = {
{ BCM2835_POWER_DOMAIN_GRAFX, BCM2835_POWER_DOMAIN_GRAFX_V3D },
{ BCM2835_POWER_DOMAIN_IMAGE, BCM2835_POWER_DOMAIN_IMAGE_PERI },
{ BCM2835_POWER_DOMAIN_IMAGE, BCM2835_POWER_DOMAIN_IMAGE_H264 },
{ BCM2835_POWER_DOMAIN_IMAGE, BCM2835_POWER_DOMAIN_IMAGE_ISP },
{ BCM2835_POWER_DOMAIN_IMAGE_PERI, BCM2835_POWER_DOMAIN_USB },
{ BCM2835_POWER_DOMAIN_IMAGE_PERI, BCM2835_POWER_DOMAIN_CAM0 },
{ BCM2835_POWER_DOMAIN_IMAGE_PERI, BCM2835_POWER_DOMAIN_CAM1 },
};
int ret = 0, i;
u32 id;
power = devm_kzalloc(dev, sizeof(*power), GFP_KERNEL);
if (!power)
return -ENOMEM;
platform_set_drvdata(pdev, power);
power->dev = dev;
power->base = pm->base;
power->asb = pm->asb;
power->rpivid_asb = pm->rpivid_asb;
id = readl(power->asb + ASB_AXI_BRDG_ID);
if (id != BCM2835_BRDG_ID /* "BRDG" */) {
dev_err(dev, "ASB register ID returned 0x%08x\n", id);
return -ENODEV;
}
if (power->rpivid_asb) {
id = readl(power->rpivid_asb + ASB_AXI_BRDG_ID);
if (id != BCM2835_BRDG_ID /* "BRDG" */) {
dev_err(dev, "RPiVid ASB register ID returned 0x%08x\n",
id);
return -ENODEV;
}
}
power->pd_xlate.domains = devm_kcalloc(dev,
ARRAY_SIZE(power_domain_names),
sizeof(*power->pd_xlate.domains),
GFP_KERNEL);
if (!power->pd_xlate.domains)
return -ENOMEM;
power->pd_xlate.num_domains = ARRAY_SIZE(power_domain_names);
for (i = 0; i < ARRAY_SIZE(power_domain_names); i++) {
ret = bcm2835_init_power_domain(power, i, power_domain_names[i]);
if (ret)
goto fail;
}
for (i = 0; i < ARRAY_SIZE(domain_deps); i++) {
pm_genpd_add_subdomain(&power->domains[domain_deps[i].parent].base,
&power->domains[domain_deps[i].child].base);
}
power->reset.owner = THIS_MODULE;
power->reset.nr_resets = BCM2835_RESET_COUNT;
power->reset.ops = &bcm2835_reset_ops;
power->reset.of_node = dev->parent->of_node;
ret = devm_reset_controller_register(dev, &power->reset);
if (ret)
goto fail;
of_genpd_add_provider_onecell(dev->parent->of_node, &power->pd_xlate);
dev_info(dev, "Broadcom BCM2835 power domains driver");
return 0;
fail:
for (i = 0; i < ARRAY_SIZE(power_domain_names); i++) {
struct generic_pm_domain *dom = &power->domains[i].base;
if (dom->name)
pm_genpd_remove(dom);
}
return ret;
}
static struct platform_driver bcm2835_power_driver = {
.probe = bcm2835_power_probe,
.driver = {
.name = "bcm2835-power",
},
};
module_platform_driver(bcm2835_power_driver);
MODULE_AUTHOR("Eric Anholt <eric@anholt.net>");
MODULE_DESCRIPTION("Driver for Broadcom BCM2835 PM power domains and reset");