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dts: rp1: Don't use DMA with UARTs

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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 <phil@raspberrypi.com>
This commit is contained in:
Phil Elwell
2025-03-26 11:28:28 +00:00
parent 9da8d6df20
commit bba53a117a
1 changed files with 3 additions and 3 deletions
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6
arch/arm64/boot/dts/broadcom/rp1.dtsi
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@@ -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;