arm: a37xx: pci: Program the data strobe for config read requests

According to the Armada 3720 Functional Specification Data Strobe applies
for both read and write config requests.

Data strobe bits configure which bytes from the start address should be
returned for read request. Set value 0xf (all 4 bits) into Data Strobe
register to read all four bytes from specified 32-bit config space
register. Same value for Data Strobe register is programmed by Linux
pci-aardvark.c driver for config read requests.

Without this patch pci-aardvark driver sets data strobe register only
during config write operations. So any followup config read operations
could result with just partial datai returned (if previous write operation
was not 32-bit wide). This patch fixes it and ensures that config read
operations always read all bytes from requested register.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>

drivers/pci/pci-aardvark.c

@@ -472,6 +472,9 @@ static int pcie_advk_read_config(const struct udevice *bus, pci_dev_t bdf,
 	advk_writel(pcie, reg, PIO_ADDR_LS);
 	advk_writel(pcie, 0, PIO_ADDR_MS);
 
+	/* Program the data strobe */
+	advk_writel(pcie, 0xf, PIO_WR_DATA_STRB);
+
 	retry_count = 0;
 
 retry: