On 2024-07-10 17:14, Philipp Puschmann wrote:
Am 10.07.24 um 16:56 schrieb Dragan Simic:
On 2024-07-10 12:20, Philipp Puschmann wrote:
Am 10.07.24 um 12:02 schrieb Diederik de Haas:
On Wednesday, 10 July 2024 11:33:56 CEST Philipp Puschmann wrote:
DMA names are required by of_dma_request_slave_channel function
that is
called during uart probe. So to enable DMA for uarts add the names
as in
the RK3568 TRM.
Setting it on channels without flow control apparently causes
issues. See
https://lore.kernel.org/linux-rockchip/20240628120130.24076-1-didi.debian@xxxxxxxxx/
Ah is see. The only problem that i have is to enable/disable dmas by
having or not having
dma-names properties, where the latter case is followed by kernel
error messages. That
is very counterintuitive. Maybe a explicit boolean like dma-broken
would be better. That
could be set on dtsi level as default and deleted on board dts if
wanted. With such
a boolean we could also prevent the misleading "dma-names property
of"
error message
and replace it with a hint that dma is disabled on purpose.
From what I've read in the prior discussions, this seems like a driver
issue, so the driver should be fixed instead.
I would tend to disagree. The serial driver just uses the generic dma
API. The error
message comes from of_dma_request_slave_channel() in
drivers/dma/of-dma.c
and is called from dma_request_chan() inn drivers/dma/dmaengine.c.
The first function expects a device tree node and "dmas" and
"dma-names" properties.
And "dma-names" is misused as "enable" switch and if not present (aka
disabled) it
dumps "dma-names property of node X missing or empty". For me it's
clear that
a clean way to disable or enable using dma via dts would be better to
tell the
of_dma_request_slave_channel function that dma is disabled on purpose,
so it
could return ENODEV but without printing a misleading error level
message.
Hmm, please give me some time to investigate it further.
Signed-off-by: Philipp Puschmann <p.puschmann@xxxxxxxxxxx>
---
arch/arm64/boot/dts/rockchip/rk356x.dtsi | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/arch/arm64/boot/dts/rockchip/rk356x.dtsi
b/arch/arm64/boot/dts/rockchip/rk356x.dtsi index
d8543b5557ee..4ae40661ca6a
100644
--- a/arch/arm64/boot/dts/rockchip/rk356x.dtsi
+++ b/arch/arm64/boot/dts/rockchip/rk356x.dtsi
@@ -489,6 +489,7 @@ uart0: serial@fdd50000 {
clocks = <&pmucru SCLK_UART0>, <&pmucru PCLK_UART0>;
clock-names = "baudclk", "apb_pclk";
dmas = <&dmac0 0>, <&dmac0 1>;
+ dma-names = "tx", "rx";
pinctrl-0 = <&uart0_xfer>;
pinctrl-names = "default";
reg-io-width = <4>;
@@ -1389,6 +1390,7 @@ uart1: serial@fe650000 {
clocks = <&cru SCLK_UART1>, <&cru PCLK_UART1>;
clock-names = "baudclk", "apb_pclk";
dmas = <&dmac0 2>, <&dmac0 3>;
+ dma-names = "tx", "rx";
pinctrl-0 = <&uart1m0_xfer>;
pinctrl-names = "default";
reg-io-width = <4>;
...
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