iMX53 dma and uart

[nicolask]

Hi,

I try to activate the DMA with UART5 on a custom board with the kernel linux-2.6.35, but when I do exchange data on uart, I have a DMA_ERROR sr1:2040  sr2:508a   (or sr1=2010 sr2:5089) .

I try to change the size of different received buffers ( UART5_DMA_RXBUFSIZE from serial.h , or  RXDMA_BUFF_SIZE from mxc_uart.c ) but nothing change, i always have the same error.

The uart in normal mode at 115200 bauds works well but i need to increase the baud rate up to 2,000,000 .

Is there any solution or patch ? I search but i don't find anything actually.

best regards

Nicolas.

[alevy]

I have just given Freescale support a version of the mxc_uart.c driver containing a number of fixes for bugs in DMA operation at high baud rates. If you ask them nicely they should be able to provide it to you.

[maheshmahadeva1]

I am not sure what the clock issue was, but DMA was re-enabled on UART 3 via a subsequent patch that also increased the UART DMA RX buffer size. Below is  the commit.

commit 191aff8468999abc730ffe4ee0b99fc6afd6a091

Author: Zhang Jiejing <jiejing.zhang@freescale.com>

Date:   Fri Apr 1 10:33:26 2011 +0800

    ENGR00140702-2 MX5: UART: enable UART3 DMA transfer

    - enable DMA transfer of UART3

    - enlarge DMA receive buffer size.

    Signed-off-by: Zhang Jiejing <jiejing.zhang@freescale.com>

diff --git a/arch/arm/mach-mx5/serial.h b/arch/arm/mach-mx5/serial.h

index 9fbb0b3..6ed55da 100644

--- a/arch/arm/mach-mx5/serial.h

+++ b/arch/arm/mach-mx5/serial.h

@@ -51,8 +51,8 @@

#define UART2_UFCR_TXTL         16

/* UART 3 configuration */

#define UART3_UCR4_CTSTL        16

-#define UART3_DMA_ENABLE       0

-#define UART3_DMA_RXBUFSIZE     1024

+#define UART3_DMA_ENABLE       1

+#define UART3_DMA_RXBUFSIZE     2048

#define UART3_UFCR_RXTL         16

#define UART3_UFCR_TXTL         16

/* UART 4 configuration */

[feifeihu]

with those UART related patches merged, the issue still exists on UART3!how can I do to solve it?

[maheshmahadeva1]

This patch was cherry-picked from the 2.6.35_maintain branch to 11.09 branch. Below is the link:

http://git.freescale.com/git/cgit.cgi/imx/linux-2.6-imx.git/log/?h=imx_2.6.35_maintain&ofs=50

[bikenomad]

Yes, I see that. However, I'm on the 2.6.35_maintain branch and am seeing the same error on UART3 (/dev/ttymxc2), which appears to be the only port with DMA enabled, but only if I get the data rate wrong:

~$ microcom -s 115200 /dev/ttymxc2

$C83.9P0.3R0.6T25.7*12

$C84.0P0.3R0.6T25.7*1C

$C84.0P0.3R0.6T25.7*1C

$C84.0P0.2R0.6T25.7*1D

$C84.0P0.2R0.6T25.7*1D

~$ microcom -s 9600 /dev/ttymxc2

[  382.075133] UART: DMA_ERROR: sr1:2040 sr2:5089

�[  382.106380] UART: DMA_ERROR: sr1:2040 sr2:5089

�[  382.169261] UART: DMA_ERROR: sr1:2040 sr2:5089

�g�3�[  382.263372] UART: DMA_ERROR: sr1:2040 sr2:5089

�?[  382.326259] UART: DMA_ERROR: sr1:2040 sr2:5089

[bikenomad]

After looking at the code, this is expected on serial errors.

[YixingKong]

Hi Nicolas, did Mahesh's answer help you? If yes, please mark your DI as Correct Answer.

[maheshmahadeva1 · Accepted solution]

Are you working of the linux source code found at the below link:

http://git.freescale.com/git/cgit.cgi/imx/linux-2.6-imx.git/log/?h=imx_2.6.35_11.09.01

I would recommend that you replicate the settings for UART3 found in serial.h for UART5.

Best regards,

-Mahesh

[nicolask]

Hi,

Yes it's from git I take the kernel, three or four months ago.

I enabled the dma for uart5 in the same way of uart3.

Actually I am on another project for the week. The next week I do anther tests.

Best regards,

Nicolas

[maheshmahadeva1]

Please get the latest code from :

http://git.freescale.com/git/cgit.cgi/imx/linux-2.6-imx.git/log/?h=imx_2.6.35_11.09.01

A recent patch was added to update UART SDMA scripts.

Best regards,

-Mahesh

[wenpengqiu]

I also met this issue in mx53 uart3: UART: DMA_ERROR: sr1:2040 sr2:508c

My uart3 connnect a bluetooth module, and only first DMAread operation occur this error, sequential DMAread successful.

I patch several commits including the one update UART SDMA scripts, but this error still occurs.

BTW, I noticed this git commit:

-------------------------------------------------------

commit a77a4c4f12640c414adf8c4381cb1d8eb8364dd0

Author: Zhang Jiejing <jiejing.zhang@freescale.com>

Date:   Wed Dec 8 20:24:04 2010 +0800

    ENGR00137669-3 MX53_SMD: workaround for UART have problem when DMA enable.

    There is a clock issue when UART3 enable DMA, so disable this.

    Signed-off-by: Zhang Jiejing <jiejing.zhang@freescale.com>

----------------------------------------------------

what's mean "a clock issue"? any detail?

BR

wenpeng

[bikenomad]

Is there any reason why this patch hasn't been applied to the imx_2.6.35_maintain branch yet?