In the Linux kernel, the following vulnerability has been resolved:
ASoC: samsung: i2s: enable op_clk in probe to balance runtime PM
The probe function puts the device into the runtime PM active state with
only the "iis" bus clock enabled, but it also sets priv->op_clk to the
parent of the RCLK_SRC mux without enabling it. The runtime PM suspend
callback disables both clocks, so the first runtime suspend after probe
disables op_clk once more than it was enabled.
On Exynos5250 Arndale both clocks resolve to the same EXYNOS_I2S_BUS gate,
so this triggers the following warning during boot:
WARNING: drivers/clk/clk.c:1270 at clk_core_disable+0xe4/0x23c, CPU#0: kworker/u8:3/45
i2s_bus already disabled
...
Workqueue: pm pm_runtime_work
Call trace:
...
clk_core_disable from clk_disable+0x28/0x34
clk_disable from i2s_runtime_suspend+0x58/0x68 [snd_soc_i2s]
i2s_runtime_suspend [snd_soc_i2s] from genpd_runtime_suspend+0xc4/0x298
genpd_runtime_suspend from __rpm_callback+0x48/0x18c
__rpm_callback from rpm_callback+0x4c/0x50
rpm_callback from rpm_suspend+0xf4/0x718
rpm_suspend from pm_runtime_work+0x9c/0xa0
...
Fix this by enabling op_clk in probe right after getting it, so the clock
state matches the runtime PM active state, and by disabling it in remove.