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Date:   Mon, 27 Apr 2020 12:57:32 +0800
From:   Jiaxun Yang <jiaxun.yang@flygoat.com>
To:     Tiezhu Yang <yangtiezhu@loongson.cn>
Cc:     Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Huacai Chen <chenhc@lemote.com>, linux-mips@vger.kernel.org,
        linux-kernel@vger.kernel.org, Xuefeng Li <lixuefeng@loongson.cn>
Subject: Re: [PATCH v4 0/3] Add basic support for LS7A bridge chip
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On Mon, 27 Apr 2020 09:31:54 +0800
Tiezhu Yang <yangtiezhu@loongson.cn> wrote:

> On 04/03/2020 05:29 PM, Tiezhu Yang wrote:
> > The LS7A bridge chip has been released for several years since the
> > second half of 2017, but it is not supported by the Linux mainline
> > kernel while it only works well with the Loongson internal kernel
> > version. When I update the latest version of Linux mainline kernel
> > on the Loongson 3A3000 CPU and LS7A bridge chip system, the boot
> > process failed and I feel depressed.
> >
> > The LS7A bridge chip is used a lot with 3A3000 or 3A4000 CPU in
> > the most Loongson desktop and sever products, it is important to
> > support LS7A bridge chip by the Linux mainline kernel.
> >
> > This patch series adds the basic support for the LS7A bridge chip,
> > the patch about vendor ID and SATA has been merged into the mainline
> > tree, the next work is to refactor the code about the interrupt
> > controller, and then power management and some other controller
> > device drivers.
> >
> > By the way, if you want the boot process is successful (just for
> > test) on the Loongson 3A3000 CPU and LS7A bridge chip system,
> > you should not only apply these patches, but also need the support
> > for SATA and interrupt controller in the v1 patch series.
> >
> > This patch series is based on mips-next.
> >
> > If you have any questions and suggestions, please let me know.
> >
> > Thanks,
> >
> > Tiezhu Yang
> >
> > v2:
> >    - The split patch series about Loongson vendor ID and SATA
> > controller has been merged into the linux-block.git by Jens Axboe
> > [1].
> >
> >    - Think about using hierarchy IRQ domain in the patch of
> > interrupt controller, and this maybe depend on the patch series by
> > Jiaxun ("Modernize Loongson64 Machine"), so the patch about
> > interrupt is not included in this v2 patch series.
> >
> > v3:
> >    - The split patch series about Loongson vendor ID and SATA
> > controller has been merged into the mainline tree [2]
> >
> >    - Modify the macro definition and add comment to make it easy to
> > read
> >
> >    - Move ls7a1000_pci_class_quirk() to fixup-loongson3.c
> >
> >    - Use PCI_VENDOR_ID_LOONGSON in pci_ids.h instead of 0x0014
> >
> > v4:
> >    - Use LS7A instead of Loongson 7A1000 in the description
> >    - Use LS7A or ls7a instead of LS7A1000 or ls7a1000 in the code
> >
> > [1]
> > https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git/commit/?h=for-next&id=9acb9fe18d86
> > https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git/commit/?h=for-next&id=e49bd683e00b
> > [2]
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9acb9fe18d86
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e49bd683e00b
> >
> > Tiezhu Yang (3):
> >    MIPS: Loongson: Get host bridge information
> >    MIPS: Loongson: Add DMA support for LS7A
> >    MIPS: Loongson: Add PCI support for LS7A
> >
> >   arch/mips/include/asm/mach-loongson64/boot_param.h | 20 +++++++
> >   arch/mips/loongson64/dma.c                         |  9 ++--
> >   arch/mips/loongson64/env.c                         | 22 ++++++++
> >   arch/mips/loongson64/init.c                        | 17 ++++++
> >   arch/mips/pci/fixup-loongson3.c                    | 12 +++++
> >   arch/mips/pci/ops-loongson3.c                      | 63
> > ++++++++++++++++++++-- 6 files changed, 136 insertions(+), 7
> > deletions(-) 
> 
> Hi Thomas,
> 
> Could you please apply the following two patches to mips-next?
> 
> [v4,1/3] MIPS: Loongson: Get host bridge information
> https://lore.kernel.org/patchwork/patch/1220009/
> 
> [v4,2/3] MIPS: Loongson: Add DMA support for LS7A
> https://lore.kernel.org/patchwork/patch/1220010/

Sorry but I really don't like the DMA patch, hard coding a config
register in platform code is not necessarily a good idea, it
create painful hell for adding new platform support.

I'm trying very hard to let all devices go through DeviceTree.

I'd suggest you to limit DMA capability on LS7A PCH instead of doing
the hack.

Or if you think the function is necessary, you can create a DeviceTree
node called "loongson,ls7a-syscon", and do whatever you like in
init_calls by parsing this node.

Also that will also block my upcoming LS2K support patches.
You can check my tree here[1].

Thanks.

[1]: https://github.com/FlyGoat/linux/commits/next-testing-2k

> 
> Thanks,
> Tiezhu Yang
> 

--
Jiaxun Yang