set lowpower mode

Ivan Ivanov5 said:

Is it correct to use in c code _BIS_SR(LPM4_bits)

You should also set GIE, either within this instruction or before. Or else no interrupt can be served and the MSP will be dormant forever.
(well, this might be intentional, e.g. if the timer is generating a constant PWM output and no changes are needed anymore. Or if the DMA handles all further work alone. Or if the MSP is just waiting for power-off.

Ivan Ivanov5 said:

What is required for this mode too ?

To really enter LPM4, no module may request ACLK or SMCLK or MCLK anymore. Either by deactivating all modules, or, in case of conditional request (only available on F5x and FR5x family) if conditional clock requests have been disabled n the power management module.

if any hardware is still in need of ACLK or SMCLK, the clock, and its oscillation source, will remain active, independently of the LPM. Also, an active debugger connection will partially prevent deeper LPMs than LPM0.