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path: root/drivers/clocksource/sh_cmt.c
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Diffstat (limited to 'drivers/clocksource/sh_cmt.c')
-rw-r--r--drivers/clocksource/sh_cmt.c34
1 files changed, 32 insertions, 2 deletions
diff --git a/drivers/clocksource/sh_cmt.c b/drivers/clocksource/sh_cmt.c
index dc7c033ef587..32a77becc098 100644
--- a/drivers/clocksource/sh_cmt.c
+++ b/drivers/clocksource/sh_cmt.c
@@ -26,6 +26,7 @@
#include <linux/clk.h>
#include <linux/irq.h>
#include <linux/err.h>
+#include <linux/delay.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/sh_timer.h>
@@ -150,13 +151,13 @@ static void sh_cmt_start_stop_ch(struct sh_cmt_priv *p, int start)
static int sh_cmt_enable(struct sh_cmt_priv *p, unsigned long *rate)
{
- int ret;
+ int k, ret;
/* enable clock */
ret = clk_enable(p->clk);
if (ret) {
dev_err(&p->pdev->dev, "cannot enable clock\n");
- return ret;
+ goto err0;
}
/* make sure channel is disabled */
@@ -174,9 +175,38 @@ static int sh_cmt_enable(struct sh_cmt_priv *p, unsigned long *rate)
sh_cmt_write(p, CMCOR, 0xffffffff);
sh_cmt_write(p, CMCNT, 0);
+ /*
+ * According to the sh73a0 user's manual, as CMCNT can be operated
+ * only by the RCLK (Pseudo 32 KHz), there's one restriction on
+ * modifying CMCNT register; two RCLK cycles are necessary before
+ * this register is either read or any modification of the value
+ * it holds is reflected in the LSI's actual operation.
+ *
+ * While at it, we're supposed to clear out the CMCNT as of this
+ * moment, so make sure it's processed properly here. This will
+ * take RCLKx2 at maximum.
+ */
+ for (k = 0; k < 100; k++) {
+ if (!sh_cmt_read(p, CMCNT))
+ break;
+ udelay(1);
+ }
+
+ if (sh_cmt_read(p, CMCNT)) {
+ dev_err(&p->pdev->dev, "cannot clear CMCNT\n");
+ ret = -ETIMEDOUT;
+ goto err1;
+ }
+
/* enable channel */
sh_cmt_start_stop_ch(p, 1);
return 0;
+ err1:
+ /* stop clock */
+ clk_disable(p->clk);
+
+ err0:
+ return ret;
}
static void sh_cmt_disable(struct sh_cmt_priv *p)
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