Re: [PATCH v2 4/4] clk: mediatek: mt8183: Add clk mux notifier for MFG mux

From: AngeloGioacchino Del Regno
Date: Mon May 23 2022 - 06:05:36 EST


Il 23/05/22 10:59, Chen-Yu Tsai ha scritto:
When the MFG PLL clock, which is upstream of the MFG clock, is changed,
the downstream clock and consumers need to be switched away from the PLL
over to a stable clock to avoid glitches.

This is done through the use of the newly added clk mux notifier. The
notifier is set on the mux itself instead of the upstream PLL, but in
practice this works, as the rate change notifitcations are propogated
throughout the sub-tree hanging off the PLL. Just before rate changes,
the MFG mux is temporarily and transparently switched to the 26 MHz
main crystal. After the rate change, the mux is switched back.

Signed-off-by: Chen-Yu Tsai <wenst@xxxxxxxxxxxx>

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>