linux-kernel - [PATCH 0/2] clk: Fix issues related to CLK_IGNORE_UNUSED failures and amlogic glitch free mux

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Message-Id: <20240929-fix_glitch_free-v1-0-22f9c36b7edf@amlogic.com>
Date: Sun, 29 Sep 2024 14:10:04 +0800
From: Chuan Liu via B4 Relay <devnull+chuan.liu.amlogic.com@...nel.org>
To: Michael Turquette <mturquette@...libre.com>, 
 Stephen Boyd <sboyd@...nel.org>, Neil Armstrong <neil.armstrong@...aro.org>, 
 Jerome Brunet <jbrunet@...libre.com>, Kevin Hilman <khilman@...libre.com>, 
 Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc: linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-amlogic@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org, 
 Chuan Liu <chuan.liu@...ogic.com>
Subject: [PATCH 0/2] clk: Fix issues related to CLK_IGNORE_UNUSED failures
 and amlogic glitch free mux

If CLK_OPS_PARENT_ENABLE is configured for clock,
clk_core_disable_unprepare() is called in clk_disable_unused_subtree().
Even clocks that are configured with CLK_IGNORE_UNUSED are disabled,
resulting in the failure of CLK_IGNORE_UNUSED.

To ensure that amlogic glitch free mux can switch clock channels
properly, add flag CLK_OPS_PARENT_ENABLE to glitch free mux. The issue
that CLK_OPS_PARENT_ENABLE in CCF causes CLK_IGNORE_UNUSED to fail is
also exposed.

glitch free mux channel switchover failure issue(Test vpu_clk on S4):
step 1:
$ cat /sys/kernel/debug/clk/vpu/clk_parent 
vpu_0
$ cat /sys/kernel/debug/clk/vpu_0/clk_rate 
399999994
$ cat /sys/kernel/debug/clk/vpu_1/clk_rate 
666666656
$ echo 1 > /sys/kernel/debug/clk/vpu/clk_prepare_enable 
$ cat /sys/kernel/debug/meson-clk-msr/clks/cts_vpu_clk
399987500       +/-12500Hz

step 2:
$ echo 0 > /sys/kernel/debug/clk/vpu/clk_prepare_enable 
$ echo 1 > /sys/kernel/debug/clk/vpu/clk_parent 
$ cat /sys/kernel/debug/clk/vpu/clk_parent 
vpu_1
$ cat /sys/kernel/debug/clk/vpu/clk_rate 
666666656
$ echo 1 > /sys/kernel/debug/clk/vpu/clk_prepare_enable 
$ cat /sys/kernel/debug/meson-clk-msr/clks/cts_vpu_clk
0       +/-3125Hz

In step2, vpu_0 is disabled, and the vpu is not switched to vpu_1. At
this time, the vpu is still connected to vpu_0 and vpu_0 is disabled at
this time, resulting in the clk-measure not measuring the clock.

Signed-off-by: Chuan Liu <chuan.liu@...ogic.com>
---
Chuan Liu (2):
      clk: Fix the CLK_IGNORE_UNUSED failure issue
      clk: meson: Fix glitch free mux related issues

 drivers/clk/clk.c                  | 67 ++++++++++++++++++++++++++++++++++++--
 drivers/clk/meson/a1-peripherals.c | 12 +++----
 drivers/clk/meson/axg.c            | 16 +++++----
 drivers/clk/meson/c3-peripherals.c |  6 ++--
 drivers/clk/meson/g12a.c           | 18 ++++++----
 drivers/clk/meson/gxbb.c           | 18 ++++++----
 drivers/clk/meson/s4-peripherals.c | 32 +++++++++---------
 7 files changed, 122 insertions(+), 47 deletions(-)
---
base-commit: e736da1956cf0880a02ec5023f3487eea7611b5f
change-id: 20240929-fix_glitch_free-290c88923c31

Best regards,
-- 
Chuan Liu <chuan.liu@...ogic.com>