linux-kernel - Re: [PATCH 06/13] clk: amlogic: Add noglitch clock driver

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Message-ID: <CAFBinCBXFxefUkNj3sqUdnTz7vf72jV_FkCP6gd2veTtLHWnBg@mail.gmail.com>
Date: Mon, 9 Feb 2026 22:51:28 +0100
From: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To: chuan.liu@...ogic.com
Cc: Neil Armstrong <neil.armstrong@...aro.org>, Michael Turquette <mturquette@...libre.com>, 
	Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	linux-amlogic@...ts.infradead.org, linux-clk@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/13] clk: amlogic: Add noglitch clock driver

Hi Chuan Liu,

On Mon, Feb 9, 2026 at 6:49 AM Chuan Liu via B4 Relay
<devnull+chuan.liu.amlogic.com@...nel.org> wrote:
[...]
> + * To prevent glitches from propagating to clk_out and affecting the normal
> + * operation of glitch-sensitive modules, the no-glitch clock must be configured
> + * following the specified sequence:
> + *   - When the clock gate is disabled: configure it as a normal composite clock
> + *     (any glitches generated will be blocked by the gate and will not
> + *     propagate to clk_out).
This part is easy and makes sense.

> + *   - When the clock gate is enabled: configure it according to the following
> + *     sequence to suppress glitches:
> + *       - Configure and enable the idle composite clock path of the
> + *         noglitch_mux with the target frequency/parent clock.
> + *       - Switch the noglitch_mux to the channel prepared in the previous step.
> + *       - Disable the clock of the original noglitch_mux channel.
> + */
>From a previous discussion it seems that in reality things need to be
handled more carefully as you previously mentioned that
CLK_SET_RATE_GATE is not good enough (the description above is what
CLK_SET_RATE_GATE already achieves).
For the more careful handling Jerome suggested using the clock
protection logic: [0]
You wanted to try it out at some point: [1]
Is the verdict that Jerome's suggestion did not work? Can you please
share some details as to why it doesn't work.


Best regards,
Martin


[0] https://lore.kernel.org/linux-amlogic/1j1pnp5sg7.fsf@starbuckisacylon.baylibre.com/
[1] https://lore.kernel.org/linux-amlogic/1639bb9d-9cb7-409f-bbf8-bfe4a5d1b8bc@amlogic.com/