Date:   Mon, 25 Mar 2019 12:11:56 +0100
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Neil Armstrong <narmstrong@...libre.com>
Cc:     Jerome Brunet <jbrunet@...libre.com>,
        linux-amlogic@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 0/4] clk: meson: fixup g12a mpll

When the g12a support has been initially submitted, the MPLL appeared
(overall) fine. At the time, the board I used was falshed with amlogic
vendor u-boot. Since then, I moved to an early version on mainline
u-boot.

While debugging audio support, I noticed that MPLL based clocks were way
above target. It appeared the fractional part of the divider was not
working.

To work properly, the MPLLs each needs an initial setting in addition to
a common one. No one likes those register sequences but sometimes, like
here for PLL clocks, there is no way around it.

The series adds the possibility to set initial register sequence for the
ee clock controller and the MPLL driver. It is then used to enable the
fractional part of the g12a MPLL.

With this series applied, the fractional part works again but we are still
seeing a significant clock jitter (+/- 1,6% for 294912KHz). Discussion
are ongoing to explain and, hopefully, solve this as well.

Jerome Brunet (4):
  clk: meson: mpll: add init callback and regs
  clk: meson: g12a: add mpll register init sequences
  clk: meson: eeclk: add init regs
  clk: meson: g12a: add controller register init

 drivers/clk/meson/clk-mpll.c    | 33 +++++++++++++++++++++++----------
 drivers/clk/meson/clk-mpll.h    |  2 ++
 drivers/clk/meson/g12a.c        | 32 +++++++++++++++++++++++++++++++-
 drivers/clk/meson/meson-eeclk.c |  3 +++
 drivers/clk/meson/meson-eeclk.h |  2 ++
 5 files changed, 61 insertions(+), 11 deletions(-)

-- 
2.20.1

Powered by blists - more mailing lists