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kernel-ark/drivers/leds/leds-renesas-tpu.c
Axel Lin 4d79833245 leds: renesas-tpu: Improve the readability to pick the lowest acceptable rate 
I spent a few minutes to understand why the code catching the mismatch case
by checking if k is 0 or not. And the code using "k - 1" as array index is
unusual.

This patch checks acceptable rate from the lowest rate, and then we don't need
to subtract k by 1. This change improves the readability.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>
2013-02-01 17:47:06 -08:00

337 lines
8.8 KiB
C
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/*
* LED control using Renesas TPU
*
* Copyright (C) 2011 Magnus Damm
*
* 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; either version 2 of the License
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/spinlock.h>
#include <linux/printk.h>
#include <linux/ioport.h>
#include <linux/io.h>
#include <linux/clk.h>
#include <linux/leds.h>
#include <linux/platform_data/leds-renesas-tpu.h>
#include <linux/gpio.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/pm_runtime.h>
#include <linux/workqueue.h>
enum r_tpu_pin { R_TPU_PIN_UNUSED, R_TPU_PIN_GPIO, R_TPU_PIN_GPIO_FN };
enum r_tpu_timer { R_TPU_TIMER_UNUSED, R_TPU_TIMER_ON };
struct r_tpu_priv {
struct led_classdev ldev;
void __iomem *mapbase;
struct clk *clk;
struct platform_device *pdev;
enum r_tpu_pin pin_state;
enum r_tpu_timer timer_state;
unsigned long min_rate;
unsigned int refresh_rate;
struct work_struct work;
enum led_brightness new_brightness;
};
static DEFINE_SPINLOCK(r_tpu_lock);
#define TSTR -1 /* Timer start register (shared register) */
#define TCR 0 /* Timer control register (+0x00) */
#define TMDR 1 /* Timer mode register (+0x04) */
#define TIOR 2 /* Timer I/O control register (+0x08) */
#define TIER 3 /* Timer interrupt enable register (+0x0c) */
#define TSR 4 /* Timer status register (+0x10) */
#define TCNT 5 /* Timer counter (+0x14) */
#define TGRA 6 /* Timer general register A (+0x18) */
#define TGRB 7 /* Timer general register B (+0x1c) */
#define TGRC 8 /* Timer general register C (+0x20) */
#define TGRD 9 /* Timer general register D (+0x24) */
static inline unsigned short r_tpu_read(struct r_tpu_priv *p, int reg_nr)
{
struct led_renesas_tpu_config *cfg = p->pdev->dev.platform_data;
void __iomem *base = p->mapbase;
unsigned long offs = reg_nr << 2;
if (reg_nr == TSTR)
return ioread16(base - cfg->channel_offset);
return ioread16(base + offs);
}
static inline void r_tpu_write(struct r_tpu_priv *p, int reg_nr,
unsigned short value)
{
struct led_renesas_tpu_config *cfg = p->pdev->dev.platform_data;
void __iomem *base = p->mapbase;
unsigned long offs = reg_nr << 2;
if (reg_nr == TSTR) {
iowrite16(value, base - cfg->channel_offset);
return;
}
iowrite16(value, base + offs);
}
static void r_tpu_start_stop_ch(struct r_tpu_priv *p, int start)
{
struct led_renesas_tpu_config *cfg = p->pdev->dev.platform_data;
unsigned long flags, value;
/* start stop register shared by multiple timer channels */
spin_lock_irqsave(&r_tpu_lock, flags);
value = r_tpu_read(p, TSTR);
if (start)
value |= 1 << cfg->timer_bit;
else
value &= ~(1 << cfg->timer_bit);
r_tpu_write(p, TSTR, value);
spin_unlock_irqrestore(&r_tpu_lock, flags);
}
static int r_tpu_enable(struct r_tpu_priv *p, enum led_brightness brightness)
{
struct led_renesas_tpu_config *cfg = p->pdev->dev.platform_data;
int prescaler[] = { 1, 4, 16, 64 };
int k, ret;
unsigned long rate, tmp;
if (p->timer_state == R_TPU_TIMER_ON)
return 0;
/* wake up device and enable clock */
pm_runtime_get_sync(&p->pdev->dev);
ret = clk_enable(p->clk);
if (ret) {
dev_err(&p->pdev->dev, "cannot enable clock\n");
return ret;
}
/* make sure channel is disabled */
r_tpu_start_stop_ch(p, 0);
/* get clock rate after enabling it */
rate = clk_get_rate(p->clk);
/* pick the lowest acceptable rate */
for (k = ARRAY_SIZE(prescaler) - 1; k >= 0; k--)
if ((rate / prescaler[k]) >= p->min_rate)
break;
if (k < 0) {
dev_err(&p->pdev->dev, "clock rate mismatch\n");
goto err0;
}
dev_dbg(&p->pdev->dev, "rate = %lu, prescaler %u\n",
rate, prescaler[k]);
/* clear TCNT on TGRB match, count on rising edge, set prescaler */
r_tpu_write(p, TCR, 0x0040 | k);
/* output 0 until TGRA, output 1 until TGRB */
r_tpu_write(p, TIOR, 0x0002);
rate /= prescaler[k] * p->refresh_rate;
r_tpu_write(p, TGRB, rate);
dev_dbg(&p->pdev->dev, "TRGB = 0x%04lx\n", rate);
tmp = (cfg->max_brightness - brightness) * rate;
r_tpu_write(p, TGRA, tmp / cfg->max_brightness);
dev_dbg(&p->pdev->dev, "TRGA = 0x%04lx\n", tmp / cfg->max_brightness);
/* PWM mode */
r_tpu_write(p, TMDR, 0x0002);
/* enable channel */
r_tpu_start_stop_ch(p, 1);
p->timer_state = R_TPU_TIMER_ON;
return 0;
err0:
clk_disable(p->clk);
pm_runtime_put_sync(&p->pdev->dev);
return -ENOTSUPP;
}
static void r_tpu_disable(struct r_tpu_priv *p)
{
if (p->timer_state == R_TPU_TIMER_UNUSED)
return;
/* disable channel */
r_tpu_start_stop_ch(p, 0);
/* stop clock and mark device as idle */
clk_disable(p->clk);
pm_runtime_put_sync(&p->pdev->dev);
p->timer_state = R_TPU_TIMER_UNUSED;
}
static void r_tpu_set_pin(struct r_tpu_priv *p, enum r_tpu_pin new_state,
enum led_brightness brightness)
{
struct led_renesas_tpu_config *cfg = p->pdev->dev.platform_data;
if (p->pin_state == new_state) {
if (p->pin_state == R_TPU_PIN_GPIO)
gpio_set_value(cfg->pin_gpio, brightness);
return;
}
if (p->pin_state == R_TPU_PIN_GPIO)
gpio_free(cfg->pin_gpio);
if (p->pin_state == R_TPU_PIN_GPIO_FN)
gpio_free(cfg->pin_gpio_fn);
if (new_state == R_TPU_PIN_GPIO)
gpio_request_one(cfg->pin_gpio, GPIOF_DIR_OUT | !!brightness,
cfg->name);
if (new_state == R_TPU_PIN_GPIO_FN)
gpio_request(cfg->pin_gpio_fn, cfg->name);
p->pin_state = new_state;
}
static void r_tpu_work(struct work_struct *work)
{
struct r_tpu_priv *p = container_of(work, struct r_tpu_priv, work);
enum led_brightness brightness = p->new_brightness;
r_tpu_disable(p);
/* off and maximum are handled as GPIO pins, in between PWM */
if ((brightness == 0) || (brightness == p->ldev.max_brightness))
r_tpu_set_pin(p, R_TPU_PIN_GPIO, brightness);
else {
r_tpu_set_pin(p, R_TPU_PIN_GPIO_FN, 0);
r_tpu_enable(p, brightness);
}
}
static void r_tpu_set_brightness(struct led_classdev *ldev,
enum led_brightness brightness)
{
struct r_tpu_priv *p = container_of(ldev, struct r_tpu_priv, ldev);
p->new_brightness = brightness;
schedule_work(&p->work);
}
static int r_tpu_probe(struct platform_device *pdev)
{
struct led_renesas_tpu_config *cfg = pdev->dev.platform_data;
struct r_tpu_priv *p;
struct resource *res;
int ret;
if (!cfg) {
dev_err(&pdev->dev, "missing platform data\n");
return -ENODEV;
}
p = devm_kzalloc(&pdev->dev, sizeof(*p), GFP_KERNEL);
if (p == NULL) {
dev_err(&pdev->dev, "failed to allocate driver data\n");
return -ENOMEM;
}
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!res) {
dev_err(&pdev->dev, "failed to get I/O memory\n");
return -ENXIO;
}
/* map memory, let mapbase point to our channel */
p->mapbase = devm_ioremap_nocache(&pdev->dev, res->start,
resource_size(res));
if (p->mapbase == NULL) {
dev_err(&pdev->dev, "failed to remap I/O memory\n");
return -ENXIO;
}
/* get hold of clock */
p->clk = devm_clk_get(&pdev->dev, NULL);
if (IS_ERR(p->clk)) {
dev_err(&pdev->dev, "cannot get clock\n");
return PTR_ERR(p->clk);
}
p->pdev = pdev;
p->pin_state = R_TPU_PIN_UNUSED;
p->timer_state = R_TPU_TIMER_UNUSED;
p->refresh_rate = cfg->refresh_rate ? cfg->refresh_rate : 100;
r_tpu_set_pin(p, R_TPU_PIN_GPIO, LED_OFF);
platform_set_drvdata(pdev, p);
INIT_WORK(&p->work, r_tpu_work);
p->ldev.name = cfg->name;
p->ldev.brightness = LED_OFF;
p->ldev.max_brightness = cfg->max_brightness;
p->ldev.brightness_set = r_tpu_set_brightness;
p->ldev.flags |= LED_CORE_SUSPENDRESUME;
ret = led_classdev_register(&pdev->dev, &p->ldev);
if (ret < 0)
goto err0;
/* max_brightness may be updated by the LED core code */
p->min_rate = p->ldev.max_brightness * p->refresh_rate;
pm_runtime_enable(&pdev->dev);
return 0;
err0:
r_tpu_set_pin(p, R_TPU_PIN_UNUSED, LED_OFF);
return ret;
}
static int r_tpu_remove(struct platform_device *pdev)
{
struct r_tpu_priv *p = platform_get_drvdata(pdev);
r_tpu_set_brightness(&p->ldev, LED_OFF);
led_classdev_unregister(&p->ldev);
cancel_work_sync(&p->work);
r_tpu_disable(p);
r_tpu_set_pin(p, R_TPU_PIN_UNUSED, LED_OFF);
pm_runtime_disable(&pdev->dev);
return 0;
}
static struct platform_driver r_tpu_device_driver = {
.probe = r_tpu_probe,
.remove = r_tpu_remove,
.driver = {
.name = "leds-renesas-tpu",
}
};
module_platform_driver(r_tpu_device_driver);
MODULE_AUTHOR("Magnus Damm");
MODULE_DESCRIPTION("Renesas TPU LED Driver");
MODULE_LICENSE("GPL v2");
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