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imx: re-work of PWM, add i.MX21 support
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* Kconfig enables now HAVE_PWM (this enables in turn the selection of
  CONFIG_BACKLIGHT_PWM)
* changes CONFIG_ARCH_MXyy to CONFIG_MACH_MXyy
* fix some register names to match those of the reference manual
* write a stub code so that the PWM can be used to program the
  LCD backlight
* convert from #ifdef CONFIG_ARCH_MXxx to cpu_is_mxXX()
* remove unneeded defines and fix 80-column "violations" of checkpatch.pl

Signed-off-by: Holger Schurig <hs4233@mail.mn-solutions.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
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Holger Schurig authored and Sascha Hauer committed May 7, 2009
1 parent 6b91edd commit c010dba
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Showing 2 changed files with 63 additions and 82 deletions.
1 change: 1 addition & 0 deletions arch/arm/plat-mxc/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,7 @@ config MXC_IRQ_PRIOR
config MXC_PWM
tristate "Enable PWM driver"
depends on ARCH_MXC
select HAVE_PWM
help
Enable support for the i.MX PWM controller(s).

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144 changes: 62 additions & 82 deletions arch/arm/plat-mxc/pwm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -15,65 +15,26 @@
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/pwm.h>
#include <mach/hardware.h>


/* i.MX1 and i.MX21 share the same PWM function block: */

#define MX1_PWMC 0x00 /* PWM Control Register */
#define MX1_PWMS 0x04 /* PWM Sample Register */
#define MX1_PWMP 0x08 /* PWM Period Register */


/* i.MX27, i.MX31, i.MX35 share the same PWM function block: */

#define MX3_PWMCR 0x00 /* PWM Control Register */
#define MX3_PWMSAR 0x0C /* PWM Sample Register */
#define MX3_PWMPR 0x10 /* PWM Period Register */
#define MX3_PWMCR_PRESCALER(x) (((x - 1) & 0xFFF) << 4)
#define MX3_PWMCR_CLKSRC_IPG_HIGH (2 << 16)
#define MX3_PWMCR_EN (1 << 0)


#if defined CONFIG_ARCH_MX1 || defined CONFIG_ARCH_MX21
#define PWM_VER_1

#define PWMCR 0x00 /* PWM Control Register */
#define PWMSR 0x04 /* PWM Sample Register */
#define PWMPR 0x08 /* PWM Period Register */
#define PWMCNR 0x0C /* PWM Counter Register */

#define PWMCR_HCTR (1 << 18) /* Halfword FIFO Data Swapping */
#define PWMCR_BCTR (1 << 17) /* Byte FIFO Data Swapping */
#define PWMCR_SWR (1 << 16) /* Software Reset */
#define PWMCR_CLKSRC_PERCLK (0 << 15) /* PERCLK Clock Source */
#define PWMCR_CLKSRC_CLK32 (1 << 15) /* 32KHz Clock Source */
#define PWMCR_PRESCALER(x) (((x - 1) & 0x7F) << 8) /* PRESCALER */
#define PWMCR_IRQ (1 << 7) /* Interrupt Request */
#define PWMCR_IRQEN (1 << 6) /* Interrupt Request Enable */
#define PWMCR_FIFOAV (1 << 5) /* FIFO Available */
#define PWMCR_EN (1 << 4) /* Enables/Disables the PWM */
#define PWMCR_REPEAT(x) (((x) & 0x03) << 2) /* Sample Repeats */
#define PWMCR_DIV(x) (((x) & 0x03) << 0) /* Clock divider 2/4/8/16 */

#define MAX_DIV (128 * 16)
#endif

#if defined CONFIG_MACH_MX27 || defined CONFIG_ARCH_MX31
#define PWM_VER_2

#define PWMCR 0x00 /* PWM Control Register */
#define PWMSR 0x04 /* PWM Status Register */
#define PWMIR 0x08 /* PWM Interrupt Register */
#define PWMSAR 0x0C /* PWM Sample Register */
#define PWMPR 0x10 /* PWM Period Register */
#define PWMCNR 0x14 /* PWM Counter Register */

#define PWMCR_EN (1 << 0) /* Enables/Disables the PWM */
#define PWMCR_REPEAT(x) (((x) & 0x03) << 1) /* Sample Repeats */
#define PWMCR_SWR (1 << 3) /* Software Reset */
#define PWMCR_PRESCALER(x) (((x - 1) & 0xFFF) << 4)/* PRESCALER */
#define PWMCR_CLKSRC(x) (((x) & 0x3) << 16)
#define PWMCR_CLKSRC_OFF (0 << 16)
#define PWMCR_CLKSRC_IPG (1 << 16)
#define PWMCR_CLKSRC_IPG_HIGH (2 << 16)
#define PWMCR_CLKSRC_CLK32 (3 << 16)
#define PWMCR_POUTC
#define PWMCR_HCTR (1 << 20) /* Halfword FIFO Data Swapping */
#define PWMCR_BCTR (1 << 21) /* Byte FIFO Data Swapping */
#define PWMCR_DBGEN (1 << 22) /* Debug Mode */
#define PWMCR_WAITEN (1 << 23) /* Wait Mode */
#define PWMCR_DOZEN (1 << 24) /* Doze Mode */
#define PWMCR_STOPEN (1 << 25) /* Stop Mode */
#define PWMCR_FWM(x) (((x) & 0x3) << 26) /* FIFO Water Mark */

#define MAX_DIV 4096
#endif

#define PWMS_SAMPLE(x) ((x) & 0xFFFF) /* Contains a two-sample word */
#define PWMP_PERIOD(x) ((x) & 0xFFFF) /* Represents the PWM's period */
#define PWMC_COUNTER(x) ((x) & 0xFFFF) /* Represents the current count value */

struct pwm_device {
struct list_head node;
Expand All @@ -91,32 +52,52 @@ struct pwm_device {

int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
{
unsigned long long c;
unsigned long period_cycles, duty_cycles, prescale;

if (pwm == NULL || period_ns == 0 || duty_ns > period_ns)
return -EINVAL;

c = clk_get_rate(pwm->clk);
c = c * period_ns;
do_div(c, 1000000000);
period_cycles = c;

prescale = period_cycles / 0x10000 + 1;

period_cycles /= prescale;
c = (unsigned long long)period_cycles * duty_ns;
do_div(c, period_ns);
duty_cycles = c;

#ifdef PWM_VER_2
writel(duty_cycles, pwm->mmio_base + PWMSAR);
writel(period_cycles, pwm->mmio_base + PWMPR);
writel(PWMCR_PRESCALER(prescale - 1) | PWMCR_CLKSRC_IPG_HIGH | PWMCR_EN,
pwm->mmio_base + PWMCR);
#elif defined PWM_VER_1
#error PWM not yet working on MX1 / MX21
#endif
if (cpu_is_mx27() || cpu_is_mx3()) {
unsigned long long c;
unsigned long period_cycles, duty_cycles, prescale;
c = clk_get_rate(pwm->clk);
c = c * period_ns;
do_div(c, 1000000000);
period_cycles = c;

prescale = period_cycles / 0x10000 + 1;

period_cycles /= prescale;
c = (unsigned long long)period_cycles * duty_ns;
do_div(c, period_ns);
duty_cycles = c;

writel(duty_cycles, pwm->mmio_base + MX3_PWMSAR);
writel(period_cycles, pwm->mmio_base + MX3_PWMPR);
writel(MX3_PWMCR_PRESCALER(prescale - 1) |
MX3_PWMCR_CLKSRC_IPG_HIGH | MX3_PWMCR_EN,
pwm->mmio_base + MX3_PWMCR);
} else if (cpu_is_mx1() || cpu_is_mx21()) {
/* The PWM subsystem allows for exact frequencies. However,
* I cannot connect a scope on my device to the PWM line and
* thus cannot provide the program the PWM controller
* exactly. Instead, I'm relying on the fact that the
* Bootloader (u-boot or WinCE+haret) has programmed the PWM
* function group already. So I'll just modify the PWM sample
* register to follow the ratio of duty_ns vs. period_ns
* accordingly.
*
* This is good enought for programming the brightness of
* the LCD backlight.
*
* The real implementation would divide PERCLK[0] first by
* both the prescaler (/1 .. /128) and then by CLKSEL
* (/2 .. /16).
*/
u32 max = readl(pwm->mmio_base + MX1_PWMP);
u32 p = max * duty_ns / period_ns;
writel(max - p, pwm->mmio_base + MX1_PWMS);
} else {
BUG();
}

return 0;
}
Expand Down Expand Up @@ -297,4 +278,3 @@ module_exit(mxc_pwm_exit);

MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");

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