ARM: mxs/clock-mx28: fix up name##_set_rate

For the lcdif clock get_rate looks as follows:

	read div from HW_CLKCTRL_DIS_LCDIF.DIV
	return clk_get_rate(clk->parent) / div

with clk->parent being ref_pix_clk on my system.

ref_pix_clk's rate depends on HW_CLKCTRL_FRAC1.PIXFRAC.

The set_rate function for lcdif does:

	parent_rate = clk_get_rate(clk->parent);
	based on that calculate frac and div such that
	  parent_rate * 18 / frac / div is near the requested rate.
	HW_CLKCTRL_FRAC1.PIXFRAC is updated with frac
	HW_CLKCTRL_DIS_LCDIF.DIV is updated with div

For this calculation to be correct parent_rate needs to be
initialized not with the clock rate of lcdif's parent (i.e. ref_pix) but
that of its grandparent (i.e. ref_pix' parent == pll0_clk).

The obvious downside of this patch is that now set_rate(lcdif) changes
its parent's rate, too.  Still this is better than a wrong rate.

Acked-by: Shawn Guo <shawn.guo@freescale.com>
LAKML-Reference: 20110225084950.GA13684@S2101-09.ap.freescale.net
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 6 insertions, 1 deletions

diff --git a/arch/arm/mach-mxs/clock-mx28.c b/arch/arm/mach-mxs/clock-mx28.c
index 1ad97fed1e94..5dcc59d5b9ec 100644
--- a/arch/arm/mach-mxs/clock-mx28.c
+++ b/arch/arm/mach-mxs/clock-mx28.c
@@ -295,11 +295,11 @@ static int name##_set_rate(struct clk *clk, unsigned long rate)		\
         unsigned long diff, parent_rate, calc_rate;                     \
         int i;                                                          \
                                                                         \
-        parent_rate = clk_get_rate(clk->parent);                        \
         div_max = BM_CLKCTRL_##dr##_DIV >> BP_CLKCTRL_##dr##_DIV;       \
         bm_busy = BM_CLKCTRL_##dr##_BUSY;                               \
                                                                         \
         if (clk->parent == &ref_xtal_clk) {                             \
+                parent_rate = clk_get_rate(clk->parent);                \
                 div = DIV_ROUND_UP(parent_rate, rate);                  \
                 if (clk == &cpu_clk) {                                  \
                         div_max = BM_CLKCTRL_CPU_DIV_XTAL >>            \
@@ -309,6 +309,11 @@ static int name##_set_rate(struct clk *clk, unsigned long rate)		\
                 if (div == 0 || div > div_max)                          \
                         return -EINVAL;                                 \
         } else {                                                        \
+                /*                                                      \
+                 * hack alert: this block modifies clk->parent, too,    \
+                 * so the base to use it the grand parent.              \
+                 */                                                     \
+                parent_rate = clk_get_rate(clk->parent->parent);        \
                 rate >>= PARENT_RATE_SHIFT;                             \
                 parent_rate >>= PARENT_RATE_SHIFT;                      \
                 diff = parent_rate;                                     \