One other point.

On Fri, May 25, 2012 at 05:48:57PM +0200, Alessandro Rubini wrote:

+/* This is a template, copied every time a new pci device appears */
+static AMBA_APB_DEVICE(pl011_pci_template, "pl011-pci", 0,
+		       0 /* base */, {0} /* irqs */, NULL /* data */);

APB device.  It's a _peripheral_, it only has a _slave_ port which can't
initiate DMA, so:

+	if (pdev->vendor == PCI_VENDOR_ID_STMICRO) {
+		/* Under sta2x11, DMA is there but limited to 512M */
+		adev->dma_mask = SZ_512M - 1;
+		adev->dev.coherent_dma_mask = SZ_512M - 1;
+	}

This is pointless and unnecessary.  The PL011 driver itself doesn't use
_this_ struct device for anything to do with DMA at all.  That's all
handled by the DMA engine's struct device.

That's true of all APB devices.  Only AHB devices with a master port can
initiate bus transactions, and hence cause accesses to other parts of the
system.