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[ 483.380456] imx-uart 21f0000.serial: Rx FIFO overrun
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When dynamic processor's voltage/frequency scaling is enabled, Linux kernel performs a lot of transactions between different [[[[FAQs_(Axel)#Q:_How_can_I_change_the_CPU_clock_frequency.3F|<code>interactive</code>]]|OPPOPPs]]. Two approaches are available to implement such transactions:
* PMIC-based: in this case an external Power Management Integrated Circuit (PMIC) is used to change the processor's voltages
* internal LDOs-based: in this case processor's internal linear regulators are used to change such voltages.
PMIC is connected to the processor via I2C bus. As such, every time a transaction is needed, several I2C packets need to be trasnmitted over I2C bus, resulting in a relatively slow overall transaction time. In case LDOs-based approach is adopted instead, transaction are quicker because LDOs configuration registers are directly accessible in the processor's address space. On the other hand, the use of LDOs has significant drawback as explained in the following section.
==Processor heating and lifetime==
Use of internal LDOs increases the power dissipation on processor side significantly. As a consequence, operating junction temperature increases as well. This fact has to be taken into consideration at system integration level, as it affects directly expected processor lifetime. For more details please refer to
