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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Sunil V L <sunilvl@ventanamicro.com>
Cc:     linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-riscv@lists.infradead.org, linux-acpi@vger.kernel.org,
        linux-pci@vger.kernel.org, linux-serial@vger.kernel.org,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        Len Brown <lenb@kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Anup Patel <anup@brainfault.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        Conor Dooley <conor.dooley@microchip.com>,
        Andrew Jones <ajones@ventanamicro.com>,
        Atish Kumar Patra <atishp@rivosinc.com>,
        Haibo Xu <haibo1.xu@intel.com>
Subject: Re: [RFC PATCH v2 11/21] PCI: MSI: Add helper function to set
 system wide MSI support
In-Reply-To: <ZT/t0UY5rbudhjfH@sunil-laptop>
References: <20231025202344.581132-1-sunilvl@ventanamicro.com>
 <20231025202344.581132-12-sunilvl@ventanamicro.com> <87a5s0yyje.ffs@tglx>
 <ZT/t0UY5rbudhjfH@sunil-laptop>
Date:   Mon, 30 Oct 2023 20:29:13 +0100
Message-ID: <874ji7zz7a.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On Mon, Oct 30 2023 at 23:24, Sunil V. L. wrote:
> On Mon, Oct 30, 2023 at 03:28:53PM +0100, Thomas Gleixner wrote:
> Just noting related discussion :
> https://www.spinics.net/lists/linux-serial/msg57616.html
>
> The MSI controller on RISC-V (IMSIC) is optional for the platform. So,
> when by default pci_msi_enable = 1 and the MSI controller is not
> discovered, we get stack trace like below.

<SNIP>

> So, what I did was, by default call pci_no_msi() to disable MSI and then
> call pci_set_msi() to enable when MSI controller is probed.

Your taste sensors should have gone out of range ...

> But I think Bjorn's suggestion to depend on PCI_BUS_FLAGS_NO_MSI may be
> better idea. In that case, we need to set bridge->msi_domain to true in
> pci_create_root_bus(). Let me know what do you prefer or if I am
> completely missing something here.

That's definitely more sensible, but as I said in the other thread, Marc
is the one who did the PCI core/bridge setup magic and he is definitely
in a better position to answer that bridge->msi_domain question.

Thanks,

        tglx