linux-kernel - Re: [PATCH v2 3/3] pwm: axi-pwmgen: fix missing separate external clock

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Message-ID: <b8b0f11c-844d-4925-a8fb-cb92cc93f8cf@baylibre.com>
Date: Fri, 23 May 2025 13:33:26 -0400
From: Trevor Gamblin <tgamblin@...libre.com>
To: David Lechner <dlechner@...libre.com>,
 Michael Hennerich <michael.hennerich@...log.com>,
 Nuno Sá <nuno.sa@...log.com>,
 Uwe Kleine-König <ukleinek@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>
Cc: linux-pwm@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] pwm: axi-pwmgen: fix missing separate external
 clock


On 2025-05-22 10:49, David Lechner wrote:
> Add proper support for external clock to the AXI PWM generator driver.
>
> In most cases, the HDL for this IP block is compiled with the default
> ASYNC_CLK_EN=1. With this option, there is a separate external clock
> that drives the PWM output separate from the peripheral clock. So the
> driver should be enabling the "axi" clock to power the peripheral and
> the "ext" clock to drive the PWM output.
>
> When ASYNC_CLK_EN=0, the "axi" clock is also used to drive the PWM
> output and there is no "ext" clock.
>
> Previously, if there was a separate external clock, users had to specify
> only the external clock and (incorrectly) omit the AXI clock in order
> to get the correct operating frequency for the PWM output.
>
> The devicetree bindings are updated to fix this shortcoming and this
> patch changes the driver to match the new bindings. To preserve
> compatibility with any existing dtbs that specify only one clock, we
> don't require the clock name on the first clock.
>
> Fixes: 41814fe5c782 ("pwm: Add driver for AXI PWM generator")
> Signed-off-by: David Lechner <dlechner@...libre.com>

Thanks for fixing this!

Reviewed-by: Trevor Gamblin <tgamblin@...libre.com>