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doc: release-notes 3.3: Document STM32 USB clock related changes

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Document recent changes about USB clock source configuration.

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>
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Erwan Gouriou 2023-01-04 14:46:41 +01:00 • committed by Fabio Baltieri
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doc/releases/release-notes-3.3.rst
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@ -418,6 +418,18 @@ Drivers and Sensors
* USB
* STM32F1: Clock bus configuration is not done automatically by driver anymore.
It is user's responsibility to configure the proper bus prescaler using clock_control
device tree node to achieve a 48MHz bus clock. Note that, in most cases, core clock
is 72MHz and default prescaler configuration is set to achieve 48MHz USB bus clock.
Prescaler only needs to be configured manually when core clock is already 48MHz.
* STM32 (non F1): Clock bus configuration is now expected to be done in device tree
using ``clocks`` node property. When a dedicated HSI 48MHz clock is available on target,
is it configured by default as the USB bus clock, but user has the ability to select
another 48MHz clock source. When no HSI48 is available, a specific 48MHz bus clock
source should be configured by user.
* W1
* Watchdog