serial: imx: Add missing .thaw_noirq hook

[ Upstream commit 4561d8008a467cb05ac632a215391d6b787f40aa ]

The following warning is seen with non-console UART instance when
system hibernates.

[   37.371969] ------------[ cut here ]------------
[   37.376599] uart3_root_clk already disabled
[   37.380810] WARNING: CPU: 0 PID: 296 at drivers/clk/clk.c:952 clk_core_disable+0xa4/0xb0
...
[   37.506986] Call trace:
[   37.509432]  clk_core_disable+0xa4/0xb0
[   37.513270]  clk_disable+0x34/0x50
[   37.516672]  imx_uart_thaw+0x38/0x5c
[   37.520250]  platform_pm_thaw+0x30/0x6c
[   37.524089]  dpm_run_callback.constprop.0+0x3c/0xd4
[   37.528972]  device_resume+0x7c/0x160
[   37.532633]  dpm_resume+0xe8/0x230
[   37.536036]  hibernation_snapshot+0x288/0x430
[   37.540397]  hibernate+0x10c/0x2e0
[   37.543798]  state_store+0xc4/0xd0
[   37.547203]  kobj_attr_store+0x1c/0x30
[   37.550953]  sysfs_kf_write+0x48/0x60
[   37.554619]  kernfs_fop_write_iter+0x118/0x1ac
[   37.559063]  new_sync_write+0xe8/0x184
[   37.562812]  vfs_write+0x230/0x290
[   37.566214]  ksys_write+0x68/0xf4
[   37.569529]  __arm64_sys_write+0x20/0x2c
[   37.573452]  invoke_syscall.constprop.0+0x50/0xf0
[   37.578156]  do_el0_svc+0x11c/0x150
[   37.581648]  el0_svc+0x30/0x140
[   37.584792]  el0t_64_sync_handler+0xe8/0xf0
[   37.588976]  el0t_64_sync+0x1a0/0x1a4
[   37.592639] ---[ end trace 56e22eec54676d75 ]---

On hibernating, pm core calls into related hooks in sequence like:

    .freeze
    .freeze_noirq
    .thaw_noirq
    .thaw

With .thaw_noirq hook being absent, the clock will be disabled in a
unbalanced call which results the warning above.

    imx_uart_freeze()
        clk_prepare_enable()
    imx_uart_suspend_noirq()
        clk_disable()
    imx_uart_thaw
        clk_disable_unprepare()

Adding the missing .thaw_noirq hook as imx_uart_resume_noirq() will have
the call sequence corrected as below and thus fix the warning.

    imx_uart_freeze()
        clk_prepare_enable()
    imx_uart_suspend_noirq()
        clk_disable()
    imx_uart_resume_noirq()
        clk_enable()
    imx_uart_thaw
        clk_disable_unprepare()

Fixes: 09df0b3464e5 ("serial: imx: fix endless loop during suspend")
Reviewed-by: Martin Kaiser <martin@kaiser.cx>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Link: https://lore.kernel.org/r/20221012121353.2346280-1-shawn.guo@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index c6a93d6..711edb8 100644 (file)
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -2563,6 +2563,7 @@ static const struct dev_pm_ops imx_uart_pm_ops = {
        .suspend_noirq = imx_uart_suspend_noirq,
        .resume_noirq = imx_uart_resume_noirq,
        .freeze_noirq = imx_uart_suspend_noirq,
+       .thaw_noirq = imx_uart_resume_noirq,
        .restore_noirq = imx_uart_resume_noirq,
        .suspend = imx_uart_suspend,
        .resume = imx_uart_resume,