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From: Heiko Stuebner <heiko@sntech.de>
To: Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Liang Chen <cl@rock-chips.com>,
	Jun Yan <jerrysteve1101@gmail.com>
Cc: Jun Yan <jerrysteve1101@gmail.com>,
	devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] arm64: dts: rockchip: Add dma-names to RK356x UART nodes
Date: Fri, 09 Oct 2026 09:19:25 +0200	[thread overview]
Message-ID: <3055334.SvYEEZNnvj@phil> (raw)
In-Reply-To: <20261009020103.364498-1-jerrysteve1101@gmail.com>

Am Freitag, 9. Oktober 2026, 04:01:02 Mitteleuropäische Sommerzeit schrieb Jun Yan:
> The RK356x UART nodes define a dmas property but omit the matching
> dma-names property, so the 8250 driver fails to request a DMA channel
> and falls back to PIO, logging:
> 
>   of_dma_request_slave_channel: dma-names property of node
>   '/serial@fe650000' missing or empty
> 
> Add the missing dma-names = "tx", "rx" to uart0 through uart9,
> matching other Rockchip SoCs such as the RK3588.
> 
> Fixes: a3adc0b9071d ("arm64: dts: rockchip: add core dtsi for RK3568 SoC")
> Signed-off-by: Jun Yan <jerrysteve1101@gmail.com>

Please don't do that. Uart dma can cause problems on uarts that don't
use flow-control, see [0]. So the solution of choice is to only enable
it for uarts connected to bluetooth on at least RK356x.


Heiko



[0] https://lore.kernel.org/linux-rockchip/CAMdYzYpXtMocCtCpZLU_xuWmOp2Ja_v0Aj0e6YFNRA-yV7u14g@mail.gmail.com/




WARNING: multiple messages have this Message-ID (diff)
From: Heiko Stuebner <heiko@sntech.de>
To: Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Liang Chen <cl@rock-chips.com>,
	Jun Yan <jerrysteve1101@gmail.com>
Cc: Jun Yan <jerrysteve1101@gmail.com>,
	devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] arm64: dts: rockchip: Add dma-names to RK356x UART nodes
Date: Fri, 09 Oct 2026 09:19:25 +0200	[thread overview]
Message-ID: <3055334.SvYEEZNnvj@phil> (raw)
In-Reply-To: <20261009020103.364498-1-jerrysteve1101@gmail.com>

Am Freitag, 9. Oktober 2026, 04:01:02 Mitteleuropäische Sommerzeit schrieb Jun Yan:
> The RK356x UART nodes define a dmas property but omit the matching
> dma-names property, so the 8250 driver fails to request a DMA channel
> and falls back to PIO, logging:
> 
>   of_dma_request_slave_channel: dma-names property of node
>   '/serial@fe650000' missing or empty
> 
> Add the missing dma-names = "tx", "rx" to uart0 through uart9,
> matching other Rockchip SoCs such as the RK3588.
> 
> Fixes: a3adc0b9071d ("arm64: dts: rockchip: add core dtsi for RK3568 SoC")
> Signed-off-by: Jun Yan <jerrysteve1101@gmail.com>

Please don't do that. Uart dma can cause problems on uarts that don't
use flow-control, see [0]. So the solution of choice is to only enable
it for uarts connected to bluetooth on at least RK356x.


Heiko



[0] https://lore.kernel.org/linux-rockchip/CAMdYzYpXtMocCtCpZLU_xuWmOp2Ja_v0Aj0e6YFNRA-yV7u14g@mail.gmail.com/



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  reply	other threads:[~2026-10-09  7:19 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-10-09  2:01 [PATCH v2] arm64: dts: rockchip: Add dma-names to RK356x UART nodes Jun Yan
2026-10-09  2:01 ` Jun Yan
2026-10-09  7:19 ` Heiko Stuebner [this message]
2026-10-09  7:19   ` Heiko Stuebner

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