linux-kernel - Re: [PATCH AUTOSEL 5.4 7/9] ACPI / PCI: fix LPIC IRQ model default PCI IRQ polarity

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Date:   Sat, 17 Dec 2022 18:05:07 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Sasha Levin <sashal@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Jianmin Lv <lvjianmin@...ngson.cn>,
        Huacai Chen <chenhuacai@...ngson.cn>, bhelgaas@...gle.com,
        rafael@...nel.org, linux-pci@...r.kernel.org,
        linux-acpi@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 5.4 7/9] ACPI / PCI: fix LPIC IRQ model default PCI IRQ polarity

On Sat, 17 Dec 2022 15:29:45 +0000,
Sasha Levin <sashal@...nel.org> wrote:
> 
> From: Jianmin Lv <lvjianmin@...ngson.cn>
> 
> [ Upstream commit d0c50cc4b957b2cf6e43cec4998d212b5abe9220 ]
> 
> On LoongArch based systems, the PCI devices (e.g. SATA controllers and
> PCI-to-PCI bridge controllers) in Loongson chipsets output high-level
> interrupt signal to the interrupt controller they are connected (see
> Loongson 7A1000 Bridge User Manual v2.00, sec 5.3, "For the bridge chip,
> AC97 DMA interrupts are edge triggered, gpio interrupts can be configured
> to be level triggered or edge triggered as needed, and the rest of the
> interrupts are level triggered and active high."), while the IRQs are
> active low from the perspective of PCI (see Conventional PCI spec r3.0,
> sec 2.2.6, "Interrupts on PCI are optional and defined as level sensitive,
> asserted low."), which means that the interrupt output of PCI devices plugged
> into PCI-to-PCI bridges of Loongson chipset will be also converted to high-level.
> So high level triggered type is required to be passed to acpi_register_gsi()
> when creating mappings for PCI devices.
> 
> Signed-off-by: Jianmin Lv <lvjianmin@...ngson.cn>
> Reviewed-by: Huacai Chen <chenhuacai@...ngson.cn>
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> Link: https://lore.kernel.org/r/20221022075955.11726-2-lvjianmin@loongson.cn
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>  drivers/acpi/pci_irq.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/acpi/pci_irq.c b/drivers/acpi/pci_irq.c
> index dea8a60e18a4..7b843a70f33d 100644
> --- a/drivers/acpi/pci_irq.c
> +++ b/drivers/acpi/pci_irq.c
> @@ -399,13 +399,15 @@ int acpi_pci_irq_enable(struct pci_dev *dev)
>  	u8 pin;
>  	int triggering = ACPI_LEVEL_SENSITIVE;
>  	/*
> -	 * On ARM systems with the GIC interrupt model, level interrupts
> +	 * On ARM systems with the GIC interrupt model, or LoongArch
> +	 * systems with the LPIC interrupt model, level interrupts
>  	 * are always polarity high by specification; PCI legacy
>  	 * IRQs lines are inverted before reaching the interrupt
>  	 * controller and must therefore be considered active high
>  	 * as default.
>  	 */
> -	int polarity = acpi_irq_model == ACPI_IRQ_MODEL_GIC ?
> +	int polarity = acpi_irq_model == ACPI_IRQ_MODEL_GIC ||
> +		       acpi_irq_model == ACPI_IRQ_MODEL_LPIC ?
>  				      ACPI_ACTIVE_HIGH : ACPI_ACTIVE_LOW;
>  	char *link = NULL;
>  	char link_desc[16];

This cannot even compile, as the *architecture* is not even supported
in 5.4.

Please drop this patch.

       M.

-- 
Without deviation from the norm, progress is not possible.