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Date:   Thu, 30 Apr 2020 11:23:25 +0800
From:   Jiaxun Yang <jiaxun.yang@flygoat.com>
To:     Tiezhu Yang <yangtiezhu@loongson.cn>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Christoph Hellwig <hch@infradead.org>,
        Huacai Chen <chenhc@lemote.com>
CC:     linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
        Xuefeng Li <lixuefeng@loongson.cn>
Subject: Re: [PATCH v6] MIPS: Loongson: Add DMA support for LS7A
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=E4=BA=8E 2020=E5=B9=B44=E6=9C=8830=E6=97=A5 GMT+08:00 =E4=B8=8A=E5=8D=881=
0:31:07, Tiezhu Yang <yangtiezhu@loongson=2Ecn> =E5=86=99=E5=88=B0:
>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=2E
>
>In order to use the default implementation of __phys_to_dma() and
>__dma_to_phys() in dma-direct=2Eh, remove CONFIG_ARCH_HAS_PHYS_TO_DMA
>and then set the bus's DMA limit to 36 bit for RS780E to maintain
>downward compatibility=2E
>
>Signed-off-by: Tiezhu Yang <yangtiezhu@loongson=2Ecn>
>---
>
>Hi Christoph and Jiaxun,
>
>Thank you very much for your suggestions=2E

I'm probably going to refine this before we implement full devicetree boot=
,
but that's in far future=2E

LGTM to me for now=2E

Thanks=2E

Reviewed-by: Jiaxun Yang <jiaxun=2Eyang@flygoat=2Ecom>

>
>v5:
>  - use the default implementation of __phys_to_dma()
>    and __dma_to_phys() in dma-direct=2Eh
>
>v6:
>  - make loongson_dma_config() static
>  - put ls7a things before rs780 things
>
> arch/mips/Kconfig                                  |  1 -
> arch/mips/include/asm/mach-loongson64/boot_param=2Eh |  5 +++++
> arch/mips/loongson64/dma=2Ec                         | 22 +++++++++++---=
--------
> arch/mips/loongson64/env=2Ec                         |  2 ++
> 4 files changed, 18 insertions(+), 12 deletions(-)
>
>diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
>index 9f15539=2E=2E12b6bdb 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=2Eh b/arch/=
mips/include/asm/mach-loongson64/boot_param=2Eh
>index f082d87=2E=2E0c07a96 100644
>--- a/arch/mips/include/asm/mach-loongson64/boot_param=2Eh
>+++ b/arch/mips/include/asm/mach-loongson64/boot_param=2Eh
>@@ -197,6 +197,7 @@ enum loongson_bridge_type {
> 	RS780E =3D 2
> };
>=20
>+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);
> };
>=20
> extern struct efi_memory_map_loongson *loongson_memmap;
> extern struct loongson_system_configuration loongson_sysconf;
>=20
>+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=2Ec b/arch/mips/loongson64/dma=2Ec
>index 5e86635=2E=2Eef40b0d 100644
>--- a/arch/mips/loongson64/dma=2Ec
>+++ b/arch/mips/loongson64/dma=2Ec
>@@ -1,24 +1,24 @@
> // SPDX-License-Identifier: GPL-2=2E0
>-#include <linux/dma-direct=2Eh>
>+#include <linux/pci=2Eh>
> #include <linux/init=2Eh>
> #include <linux/swiotlb=2Eh>
>=20
>-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 =3D (paddr >> 44) & 0x3;
>-	return ((nid << 44) ^ paddr) | (nid << 37);
> }
>=20
>-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 =3D (daddr >> 37) & 0x3;
>-	return ((nid << 37) ^ daddr) | (nid << 44);
>+	pdev->dev=2Ebus_dma_limit =3D DMA_BIT_MASK(36);
> }
>=20
>+static void loongson_dma_config(struct pci_dev *pdev)
>+{
>+	loongson_sysconf=2Edma_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=2Ec b/arch/mips/loongson64/env=2Ec
>index 71f4aaf=2E=2E496f401 100644
>--- a/arch/mips/loongson64/env=2Ec
>+++ b/arch/mips/loongson64/env=2Ec
>@@ -192,8 +192,10 @@ void __init prom_init_env(void)
> 	if (vendor =3D=3D PCI_VENDOR_ID_LOONGSON && device =3D=3D 0x7a00) {
> 		pr_info("The bridge chip is LS7A\n");
> 		loongson_sysconf=2Ebridgetype =3D LS7A;
>+		loongson_sysconf=2Edma_config =3D ls7a_dma_config;
> 	} else {
> 		pr_info("The bridge chip is RS780E or SR5690\n");
> 		loongson_sysconf=2Ebridgetype =3D RS780E;
>+		loongson_sysconf=2Edma_config =3D rs780e_dma_config;
> 	}
> }

--=20
Jiaxun Yang