PCIE link up failed when booting the kernel on IMX6QSD board

[leoluo]

Hi, all:

Anybody knows the reason of PCIE link up failed when booting the kernel?

The EP device is fine and can running on other x86 platform.

The information during the booting is :

......

PMU: registered new PMU device of type 0

Static Power Management for Freescale i.MX6

wait mode is enabled for i.MX6

cpaddr = c0880000 suspend_iram_base=c0934000

PM driver module loaded

iMX6 PCIe PCIe RC mode imx_pcie_pltfm_probe entering.

PCIE: imx_pcie_pltfm_probe start link up.

link up failed, DB_R0:0x00aafa00, DB_R1:0x08200000!

IMX PCIe port: link down!

IMX usb wakeup probe

add wake up source irq 75

IMX usb wakeup probe

cpu regulator mode:ldo_enable

i.MXC CPU frequency driver

......

[xiaoqiangyang]

Hi leo,

I met the same problem with you, and got similar error:

......

iMX6 PCIe PCIe RC mode imx_pcie_pltfm_probe entering.

PCIE: imx_pcie_pltfm_probe start link up.

link up failed, DB_R0:0x002f0200, DB_R1:0x08200000!

IMX PCIe port: link down!

I used L3.0.35_4.1.0_130816_source.tar.gz, but the problem persisted. WHere can I enable the PCIe clock output? The kernel, or the source code?

[leoluo]

Hi Xiaoqiang,

You can do it in the function "static int _clk_pcie_enable(struct clk *clk)" in the file "clock.c" in source code.

Set the "ANATOP_LVDS_CLK1_SRC_SATA" bit of the register "ANADIG_MISC1_REG" to enable the clock.

Good luck!

[xiaoqiangyang]

I checked the code and found the register "ANADIG_MISC1_REG" had been set.

static int clkpcie_enable(struct clk *clk)

{

unsigned int reg;

#ifndef CONFIG_IMX_PCIE_RC_MODE_IN_EP_RC_SYS

/* Activate LVDS CLK1 (the MiniPCIe slot clock input) */

reg = __raw_readl(ANADIG_MISC1_REG);

reg &= ~ANATOP_LVDS_CLK1_IBEN_MASK;

__raw_writel(reg, ANADIG_MISC1_REG);

reg = __raw_readl(ANADIG_MISC1_REG);

reg |= ANATOP_LVDS_CLK1_SRC_SATA;

__raw_writel(reg, ANADIG_MISC1_REG);

reg = __raw_readl(ANADIG_MISC1_REG);

reg |= ANATOP_LVDS_CLK1_OBEN_MASK;

__raw_writel(reg, ANADIG_MISC1_REG);

#endif

I can not detect any signal on pin 23,25,31,33 of mini pcie slot using signal Oscilloscope.

But during boot up, I can detect waveform for about one secend on pin 11 and 13.

Is this phenomenon normal?

[richard_zhu]

This clk would turned off if the pcie link is failed to set-up.

You should mask the link-down handler codes if you want to measure the clk signals on clk1_np when the pcie link is down.

Richard

Best Regard

[xiaoqiangyang]

Thank you,I can get the regular waveform of clk, 100M Hz, by modifing code in the function

'static void clkpcie_disable'.But why the pcie link failed to set-up?

[richard_zhu]

There is another story, what's the HW platform used by you?

[xiaoqiangyang]

My platform is MX6Q-SDP.

[richard_zhu]

No anything else?

Such as the connector, mini-pcie2std-pcie adaptor and so on.

BTW, what's kinds of ep device used at your side?

As I know that there is only mini-pcie slot on imx6 SDP board, I suspect that the quality of the pcie signals are

damaged by the HW connection between your EP device and SDP board.

Otherwise,

I believe the debug path is to first look into board and system level types of issues. Specifically:

a) Visually inspect the traces from the transmitter to the receiver and ensure the ac-coupling capacitors are connected properly.

b) Check for any DC issues.  Specifically take a volt meter and look at the resistance from the transmitter to the ac-coupling capacitor.  Then, measure from the other side of the ac-coupling capacitor to the receiver. Check if there is any large DC resistance value.

c) Check to see that the power and ground on both sides of the link are the same.  Again, using a voltmeter, check the voltage supplies at the transmitter with respect to ground.  Then probe from the ground of the transmitter to the ground of the destination of the signal and see if there is any voltage difference.

The above is the basic start to the debug which should show any low level board issues..

[xiaoqiangyang]

Hi Hongxing,

My pcie problem has been solved.Freescale sent me a new board and pcie works well. Our board is broken on hardware level.Thanks for your help!

[richard_zhu]

Great to know that.

[xiaoqiangyang]

I tested pcie by two methods, unfortunately, all failed.

First, I used a pm2 mini-pcie2std-pcie adaptor and a pcie2pci adaptor(PEX8112):

Second,I tested mini-pcie wifi module(iwl4965) directly on the mini-pcie slot.

I checked the voltages on the slot using voltmeter,I found that 1.5V(pin6) was normal,but

3.3V was always changing.During boot up,it rose to 3.3V,but for a while, it begun to drop,

until to 2.x V, is this normal?

The mini-pcie2std-pcie don't need external power supply,its conversion circuit supplies power

to std-pcie.Severl days ago, these two solutions all worked well.But in order to use usb port on

the adaptor,I connected external power(12V and 5V,connected to std-pcie directly) to the place I

marked red,then the usb port could work well.I don't know if this is the problem,but after that,

I really haven't made the pcie work.

Any suggestion ?

[richard_zhu]

what's the sw baseline used at your side?

Best Regards

Richard

[leoluo · Accepted solution]

Hongxing, thank you for your response.

I use L3.0.35_4.1.0_130816_source.tar.gz downloaded from freescale's IMX6QSD platform resource website.

Now, the problem has been solved. The PCIe clock output was not enabled in the code when IMX6 worked as RC.

[richard_zhu]

Hi Leo:
It's great to hear that the problem had been fixed.

You're welcome. J

Best Regard

Richard

[AbisaiNegrete]

Hello richard.zhu,

I have tried  to enable N6235 WiFi chip through PCIe using imx6 sabreauto board and Yocto but I have not success on this.

Please, could you check attached log and give your suggestions? After last message in console "iwlagn: Copyright(c) 2003-2011 Intel Corporation" the system does not respond and seem to be frozen.

Best Regards,

Abisai

[richard_zhu]

Can you re-try the pcie wifi tests on imx_3.0.35 4.0 or 4.1 release?

BTW, what's kinds of sabreauto board used at your side?
Rev C or later version sabreauto obard is recommended.

Best Regards

Richard

[AbisaiNegrete]

Thanks a lot Richard, the problem was I had testing Rev B, Rev C works well.

[richard_zhu]

Great.

Best Regards
Richard