Vybrid ProcessorsのトピックUART Rx with DMA

UART Rx with DMA

makotokatsukura — Wed, 23 Jul 2014 15:01:31 GMT

Dear Timesys support,

Hi,

I'm currently working with Vybrid and using Timesys Linux.

I want to use UART with DMA both TX and RX.

However, now, at Timesys Linux, UART Tx is using DMA but Rx is not using DMA.

So, can we use DMA for UART Rx?

I've checked Linux UART driver for i.MX6, original code for Vybrid UART driver,

and at that code, both UART Tx and Rx used DMA.

I'm curious why UART Rx was changed not to use DMA during porting to Vybrid.

And if I order professional service to Timesys, can you produce the UART driver that both Tx and RX are using DMA?

Thank you,

Makoto Katsukura

Re: UART Rx with DMA

naoumgitnik — Wed, 23 Jul 2014 23:55:28 GMT

Dear timesyssupport, may you reply, please?

Thanks, Naoum Gitnik.

Re: UART Rx with DMA

timesyssupport — Thu, 24 Jul 2014 20:39:49 GMT

Hello Katsukura-san,

We did not do the original porting of the UART driver to the 3.0 Vybrid kernel, so I am not aware of the reason that DMA for Rx was not ported.

Adding DMA for UART Rx is something Timesys can produce via professional services. You can contact sales@timesys.com if you would be interested in this or for more information.

Thanks,

Timesys Support

Re: UART Rx with DMA

falstaff — Tue, 29 Jul 2014 07:39:36 GMT

Hi Katsukura,

The current mainline driver has some RX DMA support, see fsl_lpuart.c:

Linux/drivers/tty/serial/fsl_lpuart.c - Linux Cross Reference - Free Electrons

Although in its current state in 3.16 the driver has some bugs. See also this discussion in the ARM Linux mailing list:

Re: fsl_lpuart/VF610: Division by zero. — ARM, OMAP, Xscale Linux Kernel

Stefan