From: Robin Murphy <robin.murphy@arm.com>
To: Chen-Yu Tsai <wens@kernel.org>, Heiko Stuebner <heiko@sntech.de>
Cc: Chen-Yu Tsai <wens@csie.org>,
linux-arm-kernel@lists.infradead.org,
linux-rockchip@lists.infradead.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64: dts: rockchip: nanopi4: decrease Bluetooth UART baud rate
Date: Wed, 6 Oct 2021 11:49:20 +0100 [thread overview]
Message-ID: <64f06ddb-cde6-d71a-7920-41c485a1d3fb@arm.com> (raw)
In-Reply-To: <20210920175647.13008-1-wens@kernel.org>
On 2021-09-20 18:56, Chen-Yu Tsai wrote:
> From: Chen-Yu Tsai <wens@csie.org>
>
> The RK3399 does not seem to be able to properly generate the required
> 64 MHz clock for the UART to operate at 4MBd.
>
> Drop the baud rate down to 3MBd, which can be used as the clock
> controller is able to produce a 48 MHz clock.
Hmm, I've been running mine this way (with DMA) for ages now :/
Looking at clk_summary, clk_uart0_src ends up at 800MHz off CPLL (same
as several other significant clocks), with clk_uart0 at an exact 64MHz
as a division of that. I stuck a scope on the UART pins of the module
and all the edges look nicely lined up to 250ns intervals.
This is with a 5.11.4 kernel, though - I wonder if the recent fractional
divider changes in the clock driver have changed anything?
Robin.
> Fixes: 3e2f0bb72be3 ("arm64: dts: rockchip: Add nanopi4 bluetooth")
> Signed-off-by: Chen-Yu Tsai <wens@csie.org>
> ---
> arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi b/arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi
> index 8c0ff6c96e03..45ff053b119d 100644
> --- a/arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi
> +++ b/arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi
> @@ -699,7 +699,7 @@ bluetooth {
> device-wakeup-gpios = <&gpio2 RK_PD2 GPIO_ACTIVE_HIGH>;
> host-wakeup-gpios = <&gpio0 RK_PA4 GPIO_ACTIVE_HIGH>;
> shutdown-gpios = <&gpio0 RK_PB1 GPIO_ACTIVE_HIGH>;
> - max-speed = <4000000>;
> + max-speed = <3000000>;
> pinctrl-names = "default";
> pinctrl-0 = <&bt_reg_on_h &bt_host_wake_l &bt_wake_l>;
> vbat-supply = <&vcc3v3_sys>;
>
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next prev parent reply other threads:[~2021-10-06 10:51 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-20 17:56 [PATCH] arm64: dts: rockchip: nanopi4: decrease Bluetooth UART baud rate Chen-Yu Tsai
2021-09-20 17:56 ` [PATCH] arm64: dts: rockchip: rk3399: Hook up DMA for UARTs Chen-Yu Tsai
2021-10-20 8:10 ` Heiko Stuebner
2021-10-06 10:49 ` Robin Murphy [this message]
2021-10-07 17:13 ` [PATCH] arm64: dts: rockchip: nanopi4: decrease Bluetooth UART baud rate Chen-Yu Tsai
2021-10-20 12:57 ` Robin Murphy
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