topic Re: i.mx6q plus uart FIFO overrun in i.MX Processors

i.mx6q plus uart FIFO overrun

linya — Mon, 24 Jul 2017 08:35:34 GMT

I migrant cpu from i.mx6q to i.mx6 plus.

the software is yocto imx_3.14.52_1.1.0_ga

I test the same software, except device tree file, on both platform.

The same rootfs and zImage, different device tree file with the same uart config.

on i.mx6q the uart run well but i.mx6q plus encounter uart fifo overrun.

the message is like bellow:

[ 424.287781] imx-uart 21ec000.serial: Rx FIFO overrun
[ 425.287739] imx-uart 21ec000.serial: Rx FIFO overrun
[ 426.287685] imx-uart 21ec000.serial: Rx FIFO overrun
[ 427.287632] imx-uart 21ec000.serial: Rx FIFO overrun
[ 428.287580] imx-uart 21ec000.serial: Rx FIFO overrun
[ 429.287530] imx-uart 21ec000.serial: Rx FIFO overrun
[ 430.287476] imx-uart 21ec000.serial: Rx FIFO overrun

I check the message:

iMX6Quad uart RX Fifo Overrun

My overall bus load is 78% on i.mx6q,

But i.mx6q plus is just 43%, it far bellow i.mx6q.

This is no look like bus load issue.

What is root cause ?

MMDC new Profiling results:
***********************
Measure time: 500ms
Total cycles count: 264066104
Busy cycles count: 114651213
Read accesses count: 8899358
Write accesses count: 6043767
Read bytes count: 422906320
Write bytes count: 266389076
Avg. Read burst size: 47
Avg. Write burst size: 44
Read: 806.63 MB/s / Write: 508.10 MB/s Total: 1314.73 MB/s
Utilization: 37%
Overall Bus Load: 43%
Bytes Access: 46

I try to change the uart Qos.

The uart is connect to AIPS_TZ1.

I check the applications processor reference manual chapter 47.3.4 NIC-specific parameters

But there is no AIPS on table 47-5

How can I change the Qos for uart?

Re: i.mx6q plus uart FIFO overrun

igorpadykov — Mon, 24 Jul 2017 10:59:02 GMT

Hi lin

reason may be delays produced by bus arbiters (NIC&NOC described in

Chapter 47 Network Interconnect Bus System). General solution is to use

hardware flow control support with rts,cts signals.

Best regards
igor
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Re: i.mx6q plus uart FIFO overrun

linya — Tue, 08 Aug 2017 08:56:07 GMT

Hi igorpadykov

How to change the uart access priority through NIC&NOC?

The uart is connect to AIPS_TZ1.

I search the technical reference manual,

But there is no any describe on NIC&NOC about AIPS_TZ1.

Re: i.mx6q plus uart FIFO overrun

igorpadykov — Tue, 08 Aug 2017 10:50:01 GMT

example to set enet priority to 3 :

/unit_tests/memtool -32 0x00247100=0x3
/unit_tests/memtool -32 0x00247104=0x3

refer to i.MX6DQ reference manual Table 45-5. QoS and tidemark parameters.

Best regards
igor

Re: i.mx6q plus uart FIFO overrun

linya — Wed, 09 Aug 2017 03:44:14 GMT

Hi igorpadykov

I am not able to find the uart or aips_tz1 item from i.MX6DQ reference manual Table 45-5.

Which item is relate to uart in Table 45-5?

Re: i.mx6q plus uart FIFO overrun

linya — Tue, 10 Oct 2017 11:13:09 GMT

Hi igorpadykov

This issue happen after run 3D test case S07_EnvironmentMapping_FB

connect ttymxc2 with 115200 bit rate data source

1. cat /dev/ttymxc2 &

2. S07_EnvironmentMapping_FB

my urat config is:

&uart3 {
   pinctrl-names = "default";
   pinctrl-0 = <&pinctrl_uart3>;
   status = "okay";
};

pinctrl_uart3: uart3grp {
fsl,pins = <
MX6QDL_PAD_EIM_D24__UART3_TX_DATA 0x1b0b1
MX6QDL_PAD_EIM_D25__UART3_RX_DATA 0x1b0b1
>;
};