topic Re: IMX6 PCIe EP Cannot configure BAR1 in i.MX Processors

IMX6 PCIe EP Cannot configure BAR1

elijahbrown — Mon, 20 Jun 2016 23:13:02 GMT

With the IMX6 configured as a PCIe endpoint, I try to setup BAR0 and BAR1 as 32 bit memory BARs. The problem is that if BAR0 is configured to be a 32 bit memory BAR it seems that whatever I set in the BAR1 mask register is ignored. This is what I do in the code:

	// setup BAR0 and its mask
	RegWrite(Registers32::PCIE_EP_BAR0, 0x0);
	RegWrite(Registers32::PCIE_EP_MASK0, 0xFFFF);

	// setup BAR1 and its mask
	RegWrite(Registers32::PCIE_EP_BAR1, 0x0);
	RegWrite(Registers32::PCIE_EP_MASK1, 0xFFFF);

When the RC enumerates the endpoint and writes 0xFFFFFFFF to each BAR and then reads them back, BAR0 returns 0xFFFF0000 as expected. But BAR1 returns 0x00000000. If I change BAR0 to be a 64 bit BAR (RegWrite(Registers32::PCIE_EP_BAR0, 0x4);) but change nothing else, then BAR1 seems to work and the RC sees it request 64K of memory as expected.

I'm using a PCIe bus analyzer to verify the config reads and writes so I know it's not an issue with the RC. These are the values actually going across the wire to and from the IMX6.

Can a freescale engineer look into this please? Both the datasheet and the linux example code do not enable BAR1 as a 32 bit BAR so I'm wondering if this has ever been tested or if there is a bug in the part itself. Thanks.

Re: IMX6 PCIe EP Cannot configure BAR1

elijahbrown — Tue, 21 Jun 2016 02:07:49 GMT

Thought I would also paste the linux demo code provided by freescale as well. Based on these comments and my experience, should we assume there is indeed a hardware issue with using BAR1, BAR3, BAR4 and BAR5?

	/* 32bit none-prefetchable 8M bytes memory on bar0 */
	writel(0x0, dbi_base + PCI_BASE_ADDRESS_0);
	writel(SZ_8M - 1, dbi_base + (1 << 12) + PCI_BASE_ADDRESS_0);

	/* None used bar1 */
	writel(0x0, dbi_base + PCI_BASE_ADDRESS_1);
	writel(0, dbi_base + (1 << 12) + PCI_BASE_ADDRESS_1);

	/* 4K bytes IO on bar2 */
	writel(0x1, dbi_base + PCI_BASE_ADDRESS_2);
	writel(SZ_4K - 1, dbi_base + (1 << 12) + PCI_BASE_ADDRESS_2);

	/*
	* 32bit prefetchable 1M bytes memory on bar3
	* FIXME BAR MASK3 is not changable, the size
	* is fixed to 256 bytes.
	*/
	writel(0x8, dbi_base + PCI_BASE_ADDRESS_3);
	writel(SZ_1M - 1, dbi_base + (1 << 12) + PCI_BASE_ADDRESS_3);

	/*
	* 64bit prefetchable 1M bytes memory on bar4-5.
	* FIXME BAR4,5 are not enabled yet
	*/
	writel(0xc, dbi_base + PCI_BASE_ADDRESS_4);
	writel(SZ_1M - 1, dbi_base + (1 << 12) + PCI_BASE_ADDRESS_4);
	writel(0, dbi_base + (1 << 12) + PCI_BASE_ADDRESS_5);

Re: IMX6 PCIe EP Cannot configure BAR1

Yuri — Tue, 21 Jun 2016 09:25:03 GMT

Hello,

From R&D:

BAR0 thru 4 are different.

BAR0+BAR1 as 64 bit addressing bar, type memory, prefetchable, mask 0xfffff, mask

writable. So Bar1 can’t be used separately.

BAR2 : 32 bit addressing , type memory, prefetchable , mask 0xfffff, mask writable

BAR3 : 32 bit addressing , type IO, mask 0xff

Have a great day,
Yuri

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Re: IMX6 PCIe EP Cannot configure BAR1

elijahbrown — Tue, 21 Jun 2016 18:09:04 GMT

Thank you. From the reference manual:

The core provides three pairs of 32-bit BARs for each implemented function. Each pair

(BARs 0 and 1, BARs 2 and 3, BARs 4 and 5) can be configured as follows:

• One 64-bit BAR: For example, BARs 0 and 1 are combined to form a single 64-bit

BAR.

• Two 32-bit BARs: For example, BARs 0 and 1 are two independent 32-bit BARs.

• One 32-bit BAR: For example, BAR 0 is a 32-bit BAR and BAR 1 is either disabled

or removed from the core altogether to reduce gate count.

So the reference manual is incorrect, the hardware is not actually capable of being configured this way?

Re: IMX6 PCIe EP Cannot configure BAR1

Yuri — Thu, 23 Jun 2016 03:58:27 GMT

Hello,

the information from R&D is declared as non-documented feature.

Please let me know if it helps.

Regards,

Yuri.