From: Stephen Boyd <sboyd@kernel.org>
To: Broadcom internal kernel review list
<bcm-kernel-feedback-list@broadcom.com>,
Florian Fainelli <f.fainelli@gmail.com>,
Ivan T. Ivanov <iivanov@suse.de>,
Maxime Ripard <maxime@cerno.tech>,
Michael Turquette <mturquette@baylibre.com>,
Nicolas Saenz Julienne <nsaenz@kernel.org>,
Ray Jui <rjui@broadcom.com>,
Scott Branden <sbranden@broadcom.com>,
Stefan Wahren <stefan.wahren@i2se.com>
Cc: Phil Elwell <phil@raspberrypi.com>,
linux-clk@vger.kernel.org, linux-rpi-kernel@lists.infradead.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5] clk: bcm2835: Round UART input clock up
Date: Fri, 30 Sep 2022 14:30:02 -0700 [thread overview]
Message-ID: <20220930213005.D07A2C433D6@smtp.kernel.org> (raw)
In-Reply-To: <20220912081306.24662-1-iivanov@suse.de>
Quoting Ivan T. Ivanov (2022-09-12 01:13:04)
> It was reported that RPi3[1] and RPi Zero 2W boards have issues with
> the Bluetooth. It turns out that when switching from initial to
> operation speed host and device no longer can talk each other because
> host uses incorrect UART baud rate.
>
> The UART driver used in this case is amba-pl011. Original fix, see
> below Github link[2], was inside pl011 module, but somehow it didn't
> look as the right place to fix. Beside that this original rounding
> function is not exactly perfect for all possible clock values. So I
> deiced to move the hack to the platform which actually need it.
>
> The UART clock is initialised to be as close to the requested
> frequency as possible without exceeding it. Now that there is a
> clock manager that returns the actual frequencies, an expected
> 48MHz clock is reported as 47999625. If the requested baud rate
> == requested clock/16, there is no headroom and the slight
> reduction in actual clock rate results in failure.
>
> If increasing a clock by less than 0.1% changes it from ..999..
> to ..000.., round it up.
>
> [1] https://bugzilla.suse.com/show_bug.cgi?id=1188238
> [2] https://github.com/raspberrypi/linux/commit/ab3f1b39537f6d3825b8873006fbe2fc5ff057b7
>
> Cc: Phil Elwell <phil@raspberrypi.com>
> Signed-off-by: Ivan T. Ivanov <iivanov@suse.de>
> Reviewed-by: Stefan Wahren <stefan.wahren@i2se.com>
> ---
Applied to clk-next
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prev parent reply other threads:[~2022-09-30 21:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-12 8:13 [PATCH v5] clk: bcm2835: Round UART input clock up Ivan T. Ivanov
2022-09-12 8:52 ` Ivan T. Ivanov
2022-09-30 21:30 ` Stephen Boyd [this message]
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