OMAP2/3: clock: fix fint calculation for DPLL_FREQSEL

In OMAP35X TRM Rev 2010-05 Figure 7-18 "DPLL With EMI Reduction
Feature", it is shown that the internal frequency is calculated by
CLK_IN/(N+1). However, the value passed to _dpll_test_fint() is
already "N+1" since Linux is using the values to divide by. In the
technical reference manual, "N" is referring to the divider's register
value (0-127).

During power management testing, it was observed that programming the
wrong jitter correction value can cause the system to become unstable
and eventually crash.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
[paul@pwsan.com: added second paragraph to commit message]
Signed-off-by: Paul Walmsley <paul@pwsan.com>

diff --git a/arch/arm/mach-omap2/clkt_dpll.c b/arch/arm/mach-omap2/clkt_dpll.c
index 337392c..acb7ae5 100644 (file)
--- a/arch/arm/mach-omap2/clkt_dpll.c
+++ b/arch/arm/mach-omap2/clkt_dpll.c
@@ -77,7 +77,7 @@ static int _dpll_test_fint(struct clk *clk, u8 n)
        dd = clk->dpll_data;
 
        /* DPLL divider must result in a valid jitter correction val */
-       fint = clk->parent->rate / (n + 1);
+       fint = clk->parent->rate / n;
        if (fint < DPLL_FINT_BAND1_MIN) {
 
                pr_debug("rejecting n=%d due to Fint failure, "