[PATCH 0/2] Meson8b: fixes for the cpu_scale_div clock

Martin Blumenstingl martin.blumenstingl at googlemail.com
Thu Sep 27 01:59:19 PDT 2018


While trying to add support for the TWD timer I found that our CPU clock
calculation (when running off the "cpu_scale_div clock) is incorrect.

The main problem was the cpu_scale_div clock:
it's divider table has an off-by-one error. the old formula was:
  parent_rate / 2 * register_value
however, testing shows that the correct formula is:
  parent_rate / 2 * (register value + 1)
See the commit message of patch #1 for a complete description of the
problem and it's history.

While looking at the "cpu_scale_div" clock I also found that it's
register width was also off-by-one, so this is fixed in a separate patch
as well.

Both patches are not critical because I haven't seen a case where u-boot
uses cpu_scale_div for the CPU clock. It's only a problem when playing
with the CPU clock in u-boot (by writing registers manually) or as soon
as we support CPU frequency scaling.


Martin Blumenstingl (2):
  clk: meson: meson8b: fix incorrect divider mapping in cpu_scale_table
  clk: meson: meson8b: fix the width of the cpu_scale_div clock

 drivers/clk/meson/meson8b.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

-- 
2.19.0




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