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Diffstat (limited to 'drivers/pwm')
-rw-r--r--drivers/pwm/pwm-imx.c45
1 files changed, 43 insertions, 2 deletions
diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c
index fb68534b098c..f8b5f109c1ab 100644
--- a/drivers/pwm/pwm-imx.c
+++ b/drivers/pwm/pwm-imx.c
@@ -14,6 +14,7 @@
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/clk.h>
+#include <linux/delay.h>
#include <linux/io.h>
#include <linux/pwm.h>
#include <linux/of.h>
@@ -30,6 +31,7 @@
/* i.MX27, i.MX31, i.MX35 share the same PWM function block: */
#define MX3_PWMCR 0x00 /* PWM Control Register */
+#define MX3_PWMSR 0x04 /* PWM Status Register */
#define MX3_PWMSAR 0x0C /* PWM Sample Register */
#define MX3_PWMPR 0x10 /* PWM Period Register */
#define MX3_PWMCR_PRESCALER(x) ((((x) - 1) & 0xFFF) << 4)
@@ -38,7 +40,12 @@
#define MX3_PWMCR_DBGEN (1 << 22)
#define MX3_PWMCR_CLKSRC_IPG_HIGH (2 << 16)
#define MX3_PWMCR_CLKSRC_IPG (1 << 16)
+#define MX3_PWMCR_SWR (1 << 3)
#define MX3_PWMCR_EN (1 << 0)
+#define MX3_PWMSR_FIFOAV_4WORDS 0x4
+#define MX3_PWMSR_FIFOAV_MASK 0x7
+
+#define MX3_PWM_SWR_LOOP 5
struct imx_chip {
struct clk *clk_per;
@@ -103,9 +110,43 @@ static int imx_pwm_config_v2(struct pwm_chip *chip,
struct pwm_device *pwm, int duty_ns, int period_ns)
{
struct imx_chip *imx = to_imx_chip(chip);
+ struct device *dev = chip->dev;
unsigned long long c;
unsigned long period_cycles, duty_cycles, prescale;
- u32 cr;
+ unsigned int period_ms;
+ bool enable = test_bit(PWMF_ENABLED, &pwm->flags);
+ int wait_count = 0, fifoav;
+ u32 cr, sr;
+
+ /*
+ * i.MX PWMv2 has a 4-word sample FIFO.
+ * In order to avoid FIFO overflow issue, we do software reset
+ * to clear all sample FIFO if the controller is disabled or
+ * wait for a full PWM cycle to get a relinquished FIFO slot
+ * when the controller is enabled and the FIFO is fully loaded.
+ */
+ if (enable) {
+ sr = readl(imx->mmio_base + MX3_PWMSR);
+ fifoav = sr & MX3_PWMSR_FIFOAV_MASK;
+ if (fifoav == MX3_PWMSR_FIFOAV_4WORDS) {
+ period_ms = DIV_ROUND_UP(pwm->period, NSEC_PER_MSEC);
+ msleep(period_ms);
+
+ sr = readl(imx->mmio_base + MX3_PWMSR);
+ if (fifoav == (sr & MX3_PWMSR_FIFOAV_MASK))
+ dev_warn(dev, "there is no free FIFO slot\n");
+ }
+ } else {
+ writel(MX3_PWMCR_SWR, imx->mmio_base + MX3_PWMCR);
+ do {
+ usleep_range(200, 1000);
+ cr = readl(imx->mmio_base + MX3_PWMCR);
+ } while ((cr & MX3_PWMCR_SWR) &&
+ (wait_count++ < MX3_PWM_SWR_LOOP));
+
+ if (cr & MX3_PWMCR_SWR)
+ dev_warn(dev, "software reset timeout\n");
+ }
c = clk_get_rate(imx->clk_per);
c = c * period_ns;
@@ -135,7 +176,7 @@ static int imx_pwm_config_v2(struct pwm_chip *chip,
MX3_PWMCR_DOZEEN | MX3_PWMCR_WAITEN |
MX3_PWMCR_DBGEN | MX3_PWMCR_CLKSRC_IPG_HIGH;
- if (test_bit(PWMF_ENABLED, &pwm->flags))
+ if (enable)
cr |= MX3_PWMCR_EN;
writel(cr, imx->mmio_base + MX3_PWMCR);