Hi,
This is a follow-up of the discussion here: https://lore.kernel.org/linux-clk/20210319150355.xzw7ikwdaga2dwhv@gilmour/
and here: https://lore.kernel.org/all/20210914093515.260031-1-maxime@cerno.tech/
While the initial proposal implemented a new API to temporarily raise and lower clock rates based on consumer workloads, Stephen suggested an alternative approach implemented here.
The main issue that needed to be addressed in our case was that in a situation where we would have multiple calls to clk_set_rate_range, we would end up with a clock at the maximum of the minimums being set. This would be expected, but the issue was that if one of the users was to relax or drop its requirements, the rate would be left unchanged, even though the ideal rate would have changed.
So something like
clk_set_rate(user1_clk, 1000); clk_set_min_rate(user1_clk, 2000); clk_set_min_rate(user2_clk, 3000); clk_set_min_rate(user2_clk, 1000);
Would leave the clock running at 3000Hz, while the minimum would now be 2000Hz.
This was mostly due to the fact that the core only triggers a rate change in clk_set_rate_range() if the current rate is outside of the boundaries, but not if it's within the new boundaries.
That series changes that and will trigger a rate change on every call, with the former rate being tried again. This way, providers have a chance to follow whatever policy they see fit for a given clock each time the boundaries change.
This series also implements some kunit tests, first to test a few rate related functions in the CCF, and then extends it to make sure that behaviour has some test coverage.
Let me know what you think Maxime
Changes from v5: - Changed clk_hw_create_clk for clk_hw_get_clk since the former isn't exported to modules. - Added fix for clk_hw_get_clk
Changes from v4: - Rename the test file - Move all the tests to the first patch, and fix them up as fixes are done - Improved the test conditions - Added more tests - Improved commit messages - Fixed a regression where two disjoints clock ranges would now be accepted
Changes from v3: - Renamed the test file and Kconfig option - Add option to .kunitconfig - Switch to kunit_kzalloc - Use KUNIT_EXPECT_* instead of KUNIT_ASSERT_* where relevant - Test directly relevant calls instead of going through a temporary variable - Switch to more precise KUNIT_ASSERT_* macros where relevant
Changes from v2: - Rebased on current next - Rewrote the whole thing according to Stephen reviews - Implemented some kunit tests
Changes from v1: - Return NULL in clk_request_start if clk pointer is NULL - Test for clk_req pointer in clk_request_done - Add another user in vc4 - Rebased on top of v5.15-rc1
Maxime Ripard (12): clk: Fix clk_hw_get_clk() when dev is NULL clk: Introduce Kunit Tests for the framework clk: Enforce that disjoints limits are invalid clk: Always clamp the rounded rate clk: Use clamp instead of open-coding our own clk: Always set the rate on clk_set_range_rate clk: Add clk_drop_range clk: bcm: rpi: Add variant structure clk: bcm: rpi: Set a default minimum rate clk: bcm: rpi: Run some clocks at the minimum rate allowed drm/vc4: Add logging and comments drm/vc4: hdmi: Remove clock rate initialization
drivers/clk/.kunitconfig | 1 + drivers/clk/Kconfig | 7 + drivers/clk/Makefile | 1 + drivers/clk/bcm/clk-raspberrypi.c | 125 ++++- drivers/clk/clk.c | 76 ++- drivers/clk/clk_test.c | 790 ++++++++++++++++++++++++++++++ drivers/gpu/drm/vc4/vc4_hdmi.c | 13 - drivers/gpu/drm/vc4/vc4_kms.c | 11 + include/linux/clk.h | 11 + 9 files changed, 980 insertions(+), 55 deletions(-) create mode 100644 drivers/clk/clk_test.c