Re: [PATCH] ARM: tegra: nyan: Enable the 32 kHz clock for the Wi-Fi module

[Volodymyr Chapman]

Dear all,

In the interest of transparency, (and to meet the kernel AI policy
outlined in Documentation/process/generated-content.rst), I was
assisted by Claude Code (Anthropic) in creating the patch described.

It inspected the device tree and clock state of the device (HP
chromebook 14 G3: nyan-blaze), identified the missing 32 kHz PMC blink
clock and drafted the change and commit message. Warm reboots were
scripted by Claude over SSH and cold boots were performed by me. I
have reviewed the change, understand it and take full responsibility,
acknowledged through my sign-off.

My best wishes,
Volodymyr

On Sat, Nov 14, 2026 at 2:13 PM Volodymyr Chapman via B4 Relay
<devnull+volodymyrchapman.gmail.com@xxxxxxxxxx> wrote:
>
> From: Volodymyr Chapman <volodymyrchapman@xxxxxxxxx>
>
> The Marvell SD8897 Wi-Fi/Bluetooth module on the Nyan Chromebooks needs
> a 32.768 kHz sleep clock, which these boards take from the PMC blink
> output (CLK_32K_OUT_PA0). Nothing in the device tree requests that
> clock, so whether it is running when the SDIO card is brought up
> depends on the state the firmware left it in. On warm reboots it is
> usually off, and every attempt to bring up the card fails with:
>
>   mmc2: error -110 whilst initialising SDIO card
>
> leaving the system without Wi-Fi. Toggling the reset GPIO on each retry
> does not help.
>
> Describe the clock in the SDIO power sequence, as the Tegra30 Asus
> Transformer and Nexus 7 device trees already do for their Wi-Fi
> modules, so that mmc-pwrseq-simple enables it before releasing the
> module from reset.
>
> Tested on an HP Chromebook 14 G3 (nyan-blaze) running v6.6.144: with
> this change Wi-Fi came up on 8 out of 8 warm reboots, against 1 out of
> 22 before, and on 5 out of 5 cold boots (4 of them on battery), and
> the clock summary shows pmc_blink enabled by pwrseq-sdhci0 (ext_clock).
> nyan-big shares this file but was not tested.
>
> Signed-off-by: Volodymyr Chapman <volodymyrchapman@xxxxxxxxx>
> ---
>  arch/arm/boot/dts/nvidia/tegra124-nyan.dtsi | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/arch/arm/boot/dts/nvidia/tegra124-nyan.dtsi b/arch/arm/boot/dts/nvidia/tegra124-nyan.dtsi
> index 89a749c..c98de0d 100644
> --- a/arch/arm/boot/dts/nvidia/tegra124-nyan.dtsi
> +++ b/arch/arm/boot/dts/nvidia/tegra124-nyan.dtsi
> @@ -645,6 +645,9 @@
>         sdhci0_pwrseq: pwrseq-sdhci0 {
>                 compatible = "mmc-pwrseq-simple";
>
> +               clocks = <&tegra_pmc TEGRA_PMC_CLK_BLINK>;
> +               clock-names = "ext_clock";
> +
>                 reset-gpios = <&gpio TEGRA_GPIO(X, 7) GPIO_ACTIVE_LOW>;
>         };
>
>
> ---
> base-commit: 97d73c8251226cf27cc6656b4c542869bb8c69fa
> change-id: 20261114-nyan-wifi-32k-9964d3513b7e
>
> Best regards,
> --
> Volodymyr Chapman <volodymyrchapman@xxxxxxxxx>
>
>