[PATCH v4 2/3] MIPS: Loongson: Add DMA support for LS7A

[Tiezhu Yang]

In the current market, the most used bridge chip on the Loongson platform
are RS780E and LS7A, the RS780E bridge chip is already supported by the
mainline kernel.

If use the default implementation of __phys_to_dma() and __dma_to_phys()
in dma-direct.h when CONFIG_ARCH_HAS_PHYS_TO_DMA is not set, it works
well used with LS7A on the Loongson single-way and multi-way platform,
and also works well used with RS780E on the Loongson single-way platform,
but the DMA address will be wrong on the non-node0 used with RS780E on
the Loongson multi-way platform.

Just as the description in the code comment, the devices get node id from
40 bit of HyperTransport bus, so we extract 2 bit node id (bit 44~45) from
48 bit address space of Loongson CPU and embed it into HyperTransport bus
(bit 37-38), this operation can be done only at the software level used
with RS780E on the Loongson multi-way platform, because it has no hardware
function to translate address of node id, this is a hardware compatibility
problem.

Device
    |
    | DMA address
    |
Host Bridge
    |
    | HT bus address (40 bit)
    |
   CPU
    |
    | physical address (48 bit)
    |
   RAM

The LS7A has dma_node_id_offset field in the DMA route config register,
the hardware can use the dma_node_id_offset to translate address of
node id automatically, so we can get correct address when just use the
dma_pfn_offset field in struct device.

For the above reasons, in order to maintain downward compatibility
to support the RS780E bridge chip, it is better to use the platform
dependent implementation of __phys_to_dma() and __dma_to_phys().

Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
---

v3:
  - Modify the macro definition NODE_ID_OFFSET_ADDR to
    make it easy to read
  - update the commit message

v4:
  - Use LS7A instead of Loongson 7A1000 in the description
  - Use LS7A or ls7a instead of LS7A1000 or ls7a1000 in the code

 arch/mips/include/asm/mach-loongson64/boot_param.h |  5 +++++
 arch/mips/loongson64/dma.c                         |  9 ++++++---
 arch/mips/loongson64/env.c                         |  2 ++
 arch/mips/loongson64/init.c                        | 17 +++++++++++++++++
 4 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/arch/mips/include/asm/mach-loongson64/boot_param.h b/arch/mips/include/asm/mach-loongson64/boot_param.h
index fc9f14b..4ac7034 100644
--- a/arch/mips/include/asm/mach-loongson64/boot_param.h
+++ b/arch/mips/include/asm/mach-loongson64/boot_param.h
@@ -221,9 +221,14 @@ struct loongson_system_configuration {
 	u32 nr_sensors;
 	struct sensor_device sensors[MAX_SENSORS];
 	u64 workarounds;
+	void (*early_config)(void);
 };
 
 extern struct efi_memory_map_loongson *loongson_memmap;
 extern struct loongson_system_configuration loongson_sysconf;
 
+extern u32 node_id_offset;
+extern void rs780e_early_config(void);
+extern void ls7a_early_config(void);
+
 #endif
diff --git a/arch/mips/loongson64/dma.c b/arch/mips/loongson64/dma.c
index 5e86635..dbfe6e8 100644
--- a/arch/mips/loongson64/dma.c
+++ b/arch/mips/loongson64/dma.c
@@ -2,21 +2,24 @@
 #include <linux/dma-direct.h>
 #include <linux/init.h>
 #include <linux/swiotlb.h>
+#include <boot_param.h>
 
 dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t paddr)
 {
 	/* We extract 2bit node id (bit 44~47, only bit 44~45 used now) from
 	 * Loongson-3's 48bit address space and embed it into 40bit */
 	long nid = (paddr >> 44) & 0x3;
-	return ((nid << 44) ^ paddr) | (nid << 37);
+
+	return ((nid << 44) ^ paddr) | (nid << node_id_offset);
 }
 
 phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t daddr)
 {
 	/* We extract 2bit node id (bit 44~47, only bit 44~45 used now) from
 	 * Loongson-3's 48bit address space and embed it into 40bit */
-	long nid = (daddr >> 37) & 0x3;
-	return ((nid << 37) ^ daddr) | (nid << 44);
+	long nid = (daddr >> node_id_offset) & 0x3;
+
+	return ((nid << node_id_offset) ^ daddr) | (nid << 44);
 }
 
 void __init plat_swiotlb_setup(void)
diff --git a/arch/mips/loongson64/env.c b/arch/mips/loongson64/env.c
index 71f4aaf..d11bc34 100644
--- a/arch/mips/loongson64/env.c
+++ b/arch/mips/loongson64/env.c
@@ -192,8 +192,10 @@ void __init prom_init_env(void)
 	if (vendor == PCI_VENDOR_ID_LOONGSON && device == 0x7a00) {
 		pr_info("The bridge chip is LS7A\n");
 		loongson_sysconf.bridgetype = LS7A;
+		loongson_sysconf.early_config = ls7a_early_config;
 	} else {
 		pr_info("The bridge chip is RS780E or SR5690\n");
 		loongson_sysconf.bridgetype = RS780E;
+		loongson_sysconf.early_config = rs780e_early_config;
 	}
 }
diff --git a/arch/mips/loongson64/init.c b/arch/mips/loongson64/init.c
index da38944..06625d6 100644
--- a/arch/mips/loongson64/init.c
+++ b/arch/mips/loongson64/init.c
@@ -13,6 +13,11 @@
 #include <asm/fw/fw.h>
 
 #include <loongson.h>
+#include <boot_param.h>
+
+#define NODE_ID_OFFSET_ADDR	((void __iomem *)TO_UNCAC(0x1001041c))
+
+u32 node_id_offset;
 
 static void __init mips_nmi_setup(void)
 {
@@ -24,6 +29,16 @@ static void __init mips_nmi_setup(void)
 	flush_icache_range((unsigned long)base, (unsigned long)base + 0x80);
 }
 
+void rs780e_early_config(void)
+{
+	node_id_offset = 37;
+}
+
+void ls7a_early_config(void)
+{
+	node_id_offset = ((readl(NODE_ID_OFFSET_ADDR) >> 8) & 0x1f) + 36;
+}
+
 void __init prom_init(void)
 {
 	fw_init_cmdline();
@@ -33,6 +48,8 @@ void __init prom_init(void)
 	set_io_port_base((unsigned long)
 		ioremap(LOONGSON_PCIIO_BASE, LOONGSON_PCIIO_SIZE));
 
+	loongson_sysconf.early_config();
+
 	prom_init_numa_memory();
 
 	/* Hardcode to CPU UART 0 */
-- 
2.1.0