Messages in this thread | | | From | Huacai Chen <> | Date | Wed, 6 May 2020 16:47:30 +0800 | Subject | Re: [PATCH v6] MIPS: Loongson: Add DMA support for LS7A |
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Hi, Tiezhu,
On Wed, May 6, 2020 at 2:39 PM Tiezhu Yang <yangtiezhu@loongson.cn> wrote: > > On 04/30/2020 02:19 PM, Huacai Chen wrote: > > Hi Christoph, > > > > On Thu, Apr 30, 2020 at 10:31 AM Tiezhu Yang <yangtiezhu@loongson.cn> wrote: > >> 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. > > I know that you want use the default implementation of __phys_to_dma() > > and __dma_to_phys() as more as possible. But, if that is "impossible" > > on Loongson-3, should we still be forced to use the default? Yes, this > > patch makes the default version work, but it limit the device's DMA > > capability, which is not what we want. > > Hi Huacai, > > We know that the AMD RS780E bridge chip has been discontinued for > some years, as time goes by, it will gradually quit the stage of > history. > > Today and in the future, the most popular used bridge chip on the > Loongson platform is LS7A, so the initial aim of this patch is to > add DMA support for LS7A, at the same time, we should maintain > downward compatibility for RS780E. > > For the above reasons, I think what you are concerned is not a > big deal. I don't think so, this is obviously a regression. If we can accept a regression of RS780E, why we still maintain Loongson-2EF rather than simply drop them?
> > Thanks, > Tiezhu Yang > > > > >> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> > >> --- > >> > >> 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 > >> >
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