From: Christoph Hellwig <hch@infradead.org>
To: Vincent Chen <vincent.chen@sifive.com>
Cc: linux-riscv@lists.infradead.org, palmer@dabbelt.com
Subject: Re: [PATCH v2] riscv: Kconfig: do not select PCI_MSI if CONIFG_PCI is enabled
Date: Wed, 21 Jul 2021 06:57:50 +0100 [thread overview]
Message-ID: <YPe3XuYfxBkbDzHf@infradead.org> (raw)
In-Reply-To: <1626838752-7013-1-git-send-email-vincent.chen@sifive.com>
On Wed, Jul 21, 2021 at 11:39:12AM +0800, Vincent Chen wrote:
> The CONFIG_PCI_MSI is used to allow device drivers to enable MSI. The MSI
> enables a device to generate an interrupt using an inbound Memory Write
> on its PCI bus instead of asserting a device IRQ pin. The whole mechanism
> needs support from the PCI controller or generic interrupt controller and
> the corresponding software driver.
>
> The RISC-V Kconfig file actively selects the PCI_MSI if users enable
> CONFIG_PCI. However, the RISC-V specification does not require every RISC-V
> platform shall have MSI support. In other words, Kconfig enables CONFIG_PCI
> to allow PCI devices to use MSI, but due to lack of MSI support, the kernel
> may not have any function to deal with the MSI from PCI devices. When this
> case happens, it leads to the following warning message displayed in
> booting a v5.10~v5.12 kernel.
So make sure the runtime detection works fine. An x86 kernel with
CONFIG_PCI_MSI also works on non-MSI systems.
NAK to this patch.
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next prev parent reply other threads:[~2021-07-21 5:58 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-21 3:39 [PATCH v2] riscv: Kconfig: do not select PCI_MSI if CONIFG_PCI is enabled Vincent Chen
2021-07-21 5:57 ` Christoph Hellwig [this message]
2021-07-22 2:21 ` Vincent Chen
2021-08-02 5:23 ` Vincent Chen
2021-08-03 8:21 ` Christoph Hellwig
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