[PATCH v6] 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.

In order to use the default implementation of __phys_to_dma() and
__dma_to_phys() in dma-direct.h, remove CONFIG_ARCH_HAS_PHYS_TO_DMA
and then set the bus's DMA limit to 36 bit for RS780E to maintain
downward compatibility.

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

Hi Christoph and Jiaxun,

Thank you very much for your suggestions.

v5:
  - use the default implementation of __phys_to_dma()
    and __dma_to_phys() in dma-direct.h

v6:
  - make loongson_dma_config() static
  - put ls7a things before rs780 things

 arch/mips/Kconfig                                  |  1 -
 arch/mips/include/asm/mach-loongson64/boot_param.h |  5 +++++
 arch/mips/loongson64/dma.c                         | 22 +++++++++++-----------
 arch/mips/loongson64/env.c                         |  2 ++
 4 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 9f15539..12b6bdb 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -1454,7 +1454,6 @@ choice
 config CPU_LOONGSON64
 	bool "Loongson 64-bit CPU"
 	depends on SYS_HAS_CPU_LOONGSON64
-	select ARCH_HAS_PHYS_TO_DMA
 	select CPU_MIPSR2
 	select CPU_HAS_PREFETCH
 	select CPU_SUPPORTS_64BIT_KERNEL
diff --git a/arch/mips/include/asm/mach-loongson64/boot_param.h b/arch/mips/include/asm/mach-loongson64/boot_param.h
index f082d87..0c07a96 100644
--- a/arch/mips/include/asm/mach-loongson64/boot_param.h
+++ b/arch/mips/include/asm/mach-loongson64/boot_param.h
@@ -197,6 +197,7 @@ enum loongson_bridge_type {
 	RS780E = 2
 };
 
+struct pci_dev;
 struct loongson_system_configuration {
 	u32 nr_cpus;
 	u32 nr_nodes;
@@ -221,9 +222,13 @@ struct loongson_system_configuration {
 	u32 nr_sensors;
 	struct sensor_device sensors[MAX_SENSORS];
 	u64 workarounds;
+	void (*dma_config)(struct pci_dev *pdev);
 };
 
 extern struct efi_memory_map_loongson *loongson_memmap;
 extern struct loongson_system_configuration loongson_sysconf;
 
+extern void ls7a_dma_config(struct pci_dev *pdev);
+extern void rs780e_dma_config(struct pci_dev *pdev);
+
 #endif
diff --git a/arch/mips/loongson64/dma.c b/arch/mips/loongson64/dma.c
index 5e86635..ef40b0d 100644
--- a/arch/mips/loongson64/dma.c
+++ b/arch/mips/loongson64/dma.c
@@ -1,24 +1,24 @@
 // SPDX-License-Identifier: GPL-2.0
-#include <linux/dma-direct.h>
+#include <linux/pci.h>
 #include <linux/init.h>
 #include <linux/swiotlb.h>
 
-dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t paddr)
+void ls7a_dma_config(struct pci_dev *pdev)
 {
-	/* 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);
 }
 
-phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t daddr)
+void rs780e_dma_config(struct pci_dev *pdev)
 {
-	/* 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);
+	pdev->dev.bus_dma_limit = DMA_BIT_MASK(36);
 }
 
+static void loongson_dma_config(struct pci_dev *pdev)
+{
+	loongson_sysconf.dma_config(pdev);
+}
+
+DECLARE_PCI_FIXUP_EARLY(PCI_ANY_ID, PCI_ANY_ID, loongson_dma_config);
+
 void __init plat_swiotlb_setup(void)
 {
 	swiotlb_init(1);
diff --git a/arch/mips/loongson64/env.c b/arch/mips/loongson64/env.c
index 71f4aaf..496f401 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.dma_config = ls7a_dma_config;
 	} else {
 		pr_info("The bridge chip is RS780E or SR5690\n");
 		loongson_sysconf.bridgetype = RS780E;
+		loongson_sysconf.dma_config = rs780e_dma_config;
 	}
 }
-- 
2.1.0