4.4-stable review patch. If anyone has any objections, please let me know.
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From: Shawn Lin shawn.lin@rock-chips.com
[ Upstream commit 1f9c63e8de3d7b377c9d74e4a17524cfb60e6384 ]
It's found that the clock phase output from clk_summary is wrong compared to the actual phase reading from the register.
cat /sys/kernel/debug/clk/clk_summary | grep sdio_sample sdio_sample 0 1 0 50000000 0 -22
It exposes an issue that clk core, clk_core_get_phase, always returns the cached core->phase which should be either updated by calling clk_set_phase or directly from the first place the clk was registered.
When registering the clk, the core->phase geting from ->get_phase() may return negative value indicating error. This is quite common since the clk's phase may be highly related to its parent chain, but it was temporarily orphan when registered, since its parent chains hadn't be ready at that time, so the clk drivers decide to return error in this case. However, if no clk_set_phase is called or maybe the ->set_phase() isn't even implemented, the core->phase would never be updated. This is wrong, and we should try to update it when all its parent chains are settled down, like the way of updating clock rate for that. But it's not deserved to complicate the code now and just update it anyway when calling clk_core_get_phase, which would be much simple and enough.
Signed-off-by: Shawn Lin shawn.lin@rock-chips.com Acked-by: Jerome Brunet jbrunet@baylibre.com Signed-off-by: Stephen Boyd sboyd@kernel.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/clk/clk.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -1905,6 +1905,9 @@ static int clk_core_get_phase(struct clk int ret;
clk_prepare_lock(); + /* Always try to update cached phase if possible */ + if (core->ops->get_phase) + core->phase = core->ops->get_phase(core->hw); ret = core->phase; clk_prepare_unlock();