[PATCH v4 3/3] PCI: imx6: Add support for i.MX6 PCIe controller

On 14/9/13 7:50 AM, Tim Harvey wrote:

Sean,

Thanks for your work - I'm glad to see an i.MX6 PCIe host controller 
driver finally getting some upstream attention!

I've tested this under several scenarios and am running into some issues.

I found that on an IMX6DL I had to enable the sata_ref_100m clock 
additionally or a readl to the host address registers would hang (like 
the core had no clock).  I've run into this before with the IMX6DL and 
don't quite understand why the core would be clocked off the sata clock.

When going through a switch (Gateworks GW5400-B has a PLX PEX8609 
8-port PCIe switch) I found that the CPU would randomly hang sometime 
after bootup.  I found that installing an abort handler (from the 
Freescale BSP) seemed to resolve this.  Additionally when going 
through a switch, I could not read config space of the switch dev or 
anything beyond it so it doesn't look like the driver supports 
switches/bridges.

As Richard Zhu mentioned, all devices should have sata_ref_100m 
enabled.  I'll make this change in v5.

I don't have a PCIe switch handy, so I can't test your handler, but the 
reasoning does make sense.  I'll add the abort handler code into the 
driver.  I'd be curious to know if this is a Designware limitation, or 
if it's the sort of thing that this hardware is capable of supporting.

Freescale recommends using the SATA clock to drive the external bus.  I 
don't quite understand the reasoning, but it seems to have to do with a 
number of dividers and multipliers it goes through, some of which are 
fixed, and they all expect a 100 MHz clock.  They are starting to change 
the names of the clocks in the documentation from "SATA" and "PCIE" to 
"100Mhz" and "125Mhz" because of the ambiguity.

--
Sean Cross