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SubjectRe: [PATCH] dts: Disable DMA support on the BK4 vf610 device's fsl_lpuart driver
Hi Robin,

> On 09/10/2019 15:30, Lukasz Majewski wrote:
> > This change disables the DMA support (RX/TX) on the NXP's fsl_lpuart
> > driver - the PIO mode is used instead. This change is necessary for
> > better robustness of BK4's device use cases with many potentially
> > interrupted short serial transfers.
> >
> > Without it the driver hangs when some distortion happens on UART
> > lines.
> >
> > Signed-off-by: Lukasz Majewski <lukma@denx.de>
> > ---
> > arch/arm/boot/dts/vf610-bk4.dts | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/arch/arm/boot/dts/vf610-bk4.dts
> > b/arch/arm/boot/dts/vf610-bk4.dts index 0f3870d3b099..ad20f3442d40
> > 100644 --- a/arch/arm/boot/dts/vf610-bk4.dts
> > +++ b/arch/arm/boot/dts/vf610-bk4.dts
> > @@ -259,24 +259,28 @@
> > &uart0 {
> > pinctrl-names = "default";
> > pinctrl-0 = <&pinctrl_uart0>;
> > + dma-names = "","";
>
> This looks like a horrible hack - is there any reason not to just
> strip things at compile-time, i.e. "/delete-property/ dmas;"?

I don't want to strip the dma-names property globally. I just want to
adjust this particular driver mode from DMA to PIO.

For my use cases - as written in the commit message - the PIO mode is
more suitable (and reliable).

>
> Robin.
>
> > status = "okay";
> > };
> >
> > &uart1 {
> > pinctrl-names = "default";
> > pinctrl-0 = <&pinctrl_uart1>;
> > + dma-names = "","";
> > status = "okay";
> > };
> >
> > &uart2 {
> > pinctrl-names = "default";
> > pinctrl-0 = <&pinctrl_uart2>;
> > + dma-names = "","";
> > status = "okay";
> > };
> >
> > &uart3 {
> > pinctrl-names = "default";
> > pinctrl-0 = <&pinctrl_uart3>;
> > + dma-names = "","";
> > status = "okay";
> > };
> >
> >




Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de
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