[0/1] clk: meson: fix PLL rate rounding

Message

Martin Blumenstingl March 24, 2019, 4:43 p.m. UTC

Hi Jerome,

can you please look at this small fix? I discovered that my Odroid-C1
wasn't booting anymore. My other Meson8m2 board was using fine.

While investigating this I found that it hangs while setting the
sys_pll_dco rate. This is important because unlike Odroid-C1 my
Meson8m2 board has a fixed regulator (and thus always runs at a
fixed CPU speed).
It always hanged while trying to set a CPU frequency of 312MHz. This
can be achieved with:
  24MHz (xtal) * 52 (m) / 1 (n) / 4 (sys_pll)
However, my added debug logging showed that it was trying to set an
M value of 51, resulting in an output frequency of 306MHz. My debug
logs showed that meson_clk_get_pll_settings() considers 1248MHz
(which is the rate requested for sys_pll_dco for a CPU frequency of
 312MHz) "worse" than 1224MHz.

I'm not sure exactly why the bug caused the board to hang, but my
patch fixes it.

Please apply this to v5.1-rc as I believe the Odroid-C1 on kernelci
also suffers from this issue.


Martin Blumenstingl (1):
  clk: meson: pll: fix rounding and setting a rate that matches
    precisely

 drivers/clk/meson/clk-pll.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)