From: Jian Hu <jian.hu@amlogic•com>
To: Jerome Brunet <jbrunet@baylibre•com>,
Jian Hu via B4 Relay <devnull+jian.hu.amlogic.com@kernel•org>
Cc: Michael Turquette <mturquette@baylibre•com>,
Stephen Boyd <sboyd@kernel•org>, Rob Herring <robh@kernel•org>,
Krzysztof Kozlowski <krzk+dt@kernel•org>,
Conor Dooley <conor+dt@kernel•org>,
Neil Armstrong <neil.armstrong@linaro•org>,
Xianwei Zhao <xianwei.zhao@amlogic•com>,
Kevin Hilman <khilman@baylibre•com>,
Martin Blumenstingl <martin.blumenstingl@googlemail•com>,
linux-kernel@vger•kernel.org, linux-clk@vger•kernel.org,
devicetree@vger•kernel.org, linux-amlogic@lists•infradead.org,
linux-arm-kernel@lists•infradead.org
Subject: Re: [PATCH 07/10] clk: amlogic: Support POWER_OF_TWO for PLL pre-divider
Date: Wed, 20 May 2026 13:47:27 +0800 [thread overview]
Message-ID: <8d89b669-e72e-4663-9596-999a12922d32@amlogic.com> (raw)
In-Reply-To: <1jy0hm6n7e.fsf@starbuckisacylon.baylibre.com>
On 5/14/2026 11:11 PM, Jerome Brunet wrote:
> [ EXTERNAL EMAIL ]
>
> On lun. 11 mai 2026 at 20:47, Jian Hu via B4 Relay <devnull+jian.hu.amlogic.com@kernel•org> wrote:
>
>> From: Jian Hu <jian.hu@amlogic•com>
>>
>> The A9 PLL pre-divider uses a division factor of 2^n to ensure a clock
>> duty cycle of 50% after predivision.
>>
>> Add flag 'CLK_MESON_PLL_N_POWER_OF_TWO' to indicate that the PLL
>> pre-divider division factor is 2^n.
> I understand what you are doing here but I have to ask why this can't be
> implemented with independent dividers that already supports power of 2 ?
If we use independent dividers, the n member would have to be removed
from meson_clk_pll_data.
However, n is referenced 35 times in clk-pll.c, which means we would
need to modify all
related logic across the file. This would be a relatively large change.
Moreover, for all Amlogic chips, the n divider is an indispensable part
of the DCO clock.
The difference between SoC generations is as follows:
Previous SoCs PLL: n = 1, 2, 3, 4... (linear divider)
A9 SoC PLL: n = 2^0, 2^1, 2^2, 2^3, 2^4... (power-of-two
divider)
Therefore, splitting out the n divider from the DCO clock might not be a
good design choice.
[...]
Best regards,
Jian
next prev parent reply other threads:[~2026-05-20 5:47 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-11 12:47 [PATCH 00/10] Add support for A9 family clock controller Jian Hu via B4 Relay
2026-05-11 12:47 ` [PATCH 01/10] dt-bindings: clock: Add Amlogic A9 SCMI " Jian Hu via B4 Relay
2026-05-11 12:47 ` [PATCH 02/10] dt-bindings: clock: Add Amlogic A9 PLL " Jian Hu via B4 Relay
2026-05-15 8:09 ` Krzysztof Kozlowski
2026-05-22 6:20 ` Jian Hu
2026-05-22 9:16 ` Krzysztof Kozlowski
2026-05-22 11:44 ` Jian Hu
2026-05-11 12:47 ` [PATCH 03/10] dt-bindings: clock: Add Amlogic A9 peripherals " Jian Hu via B4 Relay
2026-05-14 16:15 ` Jerome Brunet
2026-05-20 3:16 ` Jian Hu
2026-05-15 8:10 ` Krzysztof Kozlowski
2026-05-22 7:49 ` Jian Hu
2026-05-11 12:47 ` [PATCH 04/10] dt-bindings: clock: Add Amlogic A9 AO " Jian Hu via B4 Relay
2026-05-15 8:10 ` Krzysztof Kozlowski
2026-05-22 8:14 ` Jian Hu
2026-05-11 12:47 ` [PATCH 05/10] clk: amlogic: PLL l_detect signal supports active-high configuration Jian Hu via B4 Relay
2026-05-11 15:47 ` Brian Masney
2026-05-14 15:13 ` Jerome Brunet
2026-05-20 3:25 ` Jian Hu
2026-05-20 7:24 ` Jerome Brunet
2026-05-20 8:46 ` Jian Hu
2026-05-11 12:47 ` [PATCH 06/10] clk: amlogic: PLL reset signal supports active-low configuration Jian Hu via B4 Relay
2026-05-11 15:21 ` Brian Masney
2026-05-13 3:53 ` Jian Hu
2026-05-14 15:16 ` Jerome Brunet
2026-05-20 3:35 ` Jian Hu
2026-05-11 12:47 ` [PATCH 07/10] clk: amlogic: Support POWER_OF_TWO for PLL pre-divider Jian Hu via B4 Relay
2026-05-11 15:23 ` Brian Masney
2026-05-14 15:11 ` Jerome Brunet
2026-05-20 5:47 ` Jian Hu [this message]
2026-05-20 7:35 ` Jerome Brunet
2026-05-26 9:58 ` Jian Hu
2026-05-26 12:27 ` Jerome Brunet
2026-05-29 7:08 ` Jian Hu
2026-05-11 12:47 ` [PATCH 08/10] clk: amlogic: Add A9 PLL clock controller driver Jian Hu via B4 Relay
2026-05-11 15:36 ` Brian Masney
2026-05-13 7:25 ` Jian Hu
2026-05-14 16:12 ` Jerome Brunet
2026-05-20 7:33 ` Jian Hu
2026-05-11 12:47 ` [PATCH 09/10] clk: amlogic: Add A9 peripherals " Jian Hu via B4 Relay
2026-05-11 15:42 ` Brian Masney
2026-05-13 8:50 ` Jian Hu
2026-05-11 12:47 ` [PATCH 10/10] clk: amlogic: Add A9 AO " Jian Hu via B4 Relay
2026-05-11 15:45 ` Brian Masney
2026-05-13 9:19 ` Jian Hu
2026-05-14 16:27 ` Jerome Brunet
2026-05-20 7:37 ` Jian Hu
2026-05-26 7:33 ` [PATCH 00/10] Add support for A9 family clock controller Jerome Brunet
2026-05-26 10:05 ` Jian Hu
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