diff options
Diffstat (limited to 'drivers/clocksource')
| -rw-r--r-- | drivers/clocksource/sh_cmt.c | 34 |
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) |