[PATCH v3 2/5] MIPS: ralink: implement 'pcibios_root_bridge_prepare()'

[Sergio Paracuellos <sergio.paracuellos@gmail.com>]

PCI core code call 'pcibios_root_bridge_prepare()' function inside function
'pci_register_host_bridge()'. This point is very good way to properly enter
into this MIPS ralink specific code to properly setup I/O coherency units
with PCI memory addresses.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
---
 arch/mips/ralink/mt7621.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/arch/mips/ralink/mt7621.c b/arch/mips/ralink/mt7621.c
index bd71f5b14238..d6efffd4dd20 100644
--- a/arch/mips/ralink/mt7621.c
+++ b/arch/mips/ralink/mt7621.c
@@ -10,6 +10,8 @@
 #include <linux/slab.h>
 #include <linux/sys_soc.h>
 #include <linux/memblock.h>
+#include <linux/pci.h>
+#include <linux/bug.h>
 
 #include <asm/bootinfo.h>
 #include <asm/mipsregs.h>
@@ -22,6 +24,35 @@
 
 static void *detect_magic __initdata = detect_memory_region;
 
+int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge)
+{
+	struct resource_entry *entry;
+	resource_size_t mask;
+
+	entry = resource_list_first_type(&bridge->windows, IORESOURCE_MEM);
+	if (!entry) {
+		pr_err("Cannot get memory resource\n");
+		return -EINVAL;
+	}
+
+	if (mips_cps_numiocu(0)) {
+		/*
+		 * Hardware doesn't accept mask values with 1s after
+		 * 0s (e.g. 0xffef), so warn if that's happen
+		 */
+		mask = ~(entry->res->end - entry->res->start) & CM_GCR_REGn_MASK_ADDRMASK;
+		WARN_ON(mask && BIT(ffz(~mask)) - 1 != ~mask);
+
+		write_gcr_reg1_base(entry->res->start);
+		write_gcr_reg1_mask(mask | CM_GCR_REGn_MASK_CMTGT_IOCU0);
+		pr_info("PCI coherence region base: 0x%08llx, mask/settings: 0x%08llx\n",
+			(unsigned long long)read_gcr_reg1_base(),
+			(unsigned long long)read_gcr_reg1_mask());
+	}
+
+	return 0;
+}
+
 phys_addr_t mips_cpc_default_phys_base(void)
 {
 	panic("Cannot detect cpc address");
-- 
2.33.0