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- From bba53a117a4a5c29da892962332ff1605990e17a Mon Sep 17 00:00:00 2001
- From: Phil Elwell <[email protected]>
- Date: Wed, 26 Mar 2025 11:28:28 +0000
- Subject: [PATCH] dts: rp1: Don't use DMA with UARTs
- DMA has been enabled on RP1's UART0, but with mixed success. Transmits
- seem to work, but the DMA interface is not well suited to receiving
- arbitrary amounts of data. In particular, the PL011 driver is slow to
- pass on the received data, batching it into large blocks.
- On balance, it's better to just disable the DMA support. As with the
- other UARTs, the required runes are left in the DTS as comments.
- Signed-off-by: Phil Elwell <[email protected]>
- ---
- arch/arm64/boot/dts/broadcom/rp1.dtsi | 6 +++---
- 1 file changed, 3 insertions(+), 3 deletions(-)
- --- a/arch/arm64/boot/dts/broadcom/rp1.dtsi
- +++ b/arch/arm64/boot/dts/broadcom/rp1.dtsi
- @@ -65,9 +65,9 @@
- interrupts = <RP1_INT_UART0 IRQ_TYPE_LEVEL_HIGH>;
- clocks = <&rp1_clocks RP1_CLK_UART &rp1_clocks RP1_PLL_SYS_PRI_PH>;
- clock-names = "uartclk", "apb_pclk";
- - dmas = <&rp1_dma RP1_DMA_UART0_TX>,
- - <&rp1_dma RP1_DMA_UART0_RX>;
- - dma-names = "tx", "rx";
- + // dmas = <&rp1_dma RP1_DMA_UART0_TX>,
- + // <&rp1_dma RP1_DMA_UART0_RX>;
- + // dma-names = "tx", "rx";
- pinctrl-names = "default";
- arm,primecell-periphid = <0x00341011>;
- uart-has-rtscts;
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