at_91 serial driver (for Atmel AT91RM9200)

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I'm wondering about using the Atmel AT91RM9200 under Linux for an
embedded application. Among others, I need to run serial communication
at 76800 bits/s over one of the USARTs.

The RM9200's USARTs have no FIFO and at that speed, I guess I need DMA
in order not to loose bytes because of Linux's interrupt latency (>130
us in some cases I guess).

I have read that in the serial_usart3 driver used for AVR32
( ), the
incoming DMA "buffer is split in half so that an interrupt fires when
half the buffer has been filled up and the driver can start consuming
the data and eventually re-use the buffer. In addition, the USART module
is set up to fire an interrupt when there is data in the buffer, but no
additional data has been received within a certain timeout."

This sounds perfect, then I have to worry neither about the risk of
delaying too much incoming bytes because the DMA buffer is not full nor
about loosing some bytes (since I guess that I can choose the size of
the DMA buffer).

What I'm wondering is whether the at_91 serial driver which is included
in the vanilla kernel (I have read it is included in the main tree from
2.6.16) also does that.

Does anybody here have some experience with that kind of issues?

Thanks in advance,

Best regards,

Alain Mosnier

Re: at_91 serial driver (for Atmel AT91RM9200)
BTW, does anyone know why seems to be down?

Is there a better newsgroup/mailing list to post questions about such a
topic (serial driver for ARM9, or more generally for UART without FIFO
and/or with DMA)?


Alain Mosnier

Re: at_91 serial driver (for Atmel AT91RM9200) /

The mailling at this web site probably the main place for information
about arm linux. There have been some discussions about a AT91RM9200
serial port driver that is DMA enabled.

Alain Mosnier wrote:
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Re: at_91 serial driver (for Atmel AT91RM9200)
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searching this site, I don't find a way to subscribe to the mailing
lists. How can this be done ?


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