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From: Lucas Tanure <tanure@linux.com>
To: Neil Armstrong <neil.armstrong@linaro.org>,
	Kevin Hilman <khilman@baylibre.com>,
	Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org,
	Xianwei Zhao <xianwei.zhao@amlogic.com>,
	linux-amlogic@lists.infradead.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH 0/2] arm64: dts: amlogic: t7: fix UART clock and SD card recovery
Date: Tue, 18 Aug 2026 20:11:57 +0100	[thread overview]
Message-ID: <20260818191159.11523-1-tanure@linux.com> (raw)

Two fixes found while booting mainline on a Khadas VIM4.

The first one wires uart_a to the real UART bus clock. It was pointed at
the 24MHz crystal as a placeholder, because the T7 clock controller
driver did not exist when these boards were added. That leaves the real
clock without a user, so the kernel turns it off when it disables unused
clocks at the end of boot, and the board hangs with the console gone.

The second one drops regulator-always-on from the SD card supply. A card
that refuses the 1.8V UHS switch can only be recovered by removing its
power, which that property prevents, so the card never initialises and
the MMC core retries forever.

Both were tested on a Khadas VIM4 booting v7.2 from the SD card.

Lucas Tanure (2):
  arm64: dts: amlogic: t7: use the real UART pclk
  arm64: dts: amlogic: t7: khadas-vim4: allow the SD card to be power
    cycled

 arch/arm64/boot/dts/amlogic/amlogic-t7-a311d2-an400.dts       | 2 --
 arch/arm64/boot/dts/amlogic/amlogic-t7-a311d2-khadas-vim4.dts | 3 ---
 arch/arm64/boot/dts/amlogic/amlogic-t7.dtsi                   | 4 ++++
 3 files changed, 4 insertions(+), 5 deletions(-)

--
2.55.0


             reply	other threads:[~2026-08-18 19:12 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-18 19:11 Lucas Tanure [this message]
2026-08-18 19:11 ` [PATCH 1/2] arm64: dts: amlogic: t7: use the real UART pclk Lucas Tanure
2026-08-19  2:39   ` Xianwei Zhao
2026-08-18 19:11 ` [PATCH 2/2] arm64: dts: amlogic: t7: khadas-vim4: allow the SD card to be power cycled Lucas Tanure

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