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Date:   Fri, 07 May 2021 11:16:58 +0100
Message-ID: <87czu2q25h.wl-maz@kernel.org>
From:   Marc Zyngier <maz@kernel.org>
To:     Pali =?UTF-8?B?Um9ow6Fy?= <pali@kernel.org>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
        Rob Herring <robh@kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Russell King <rmk+kernel@armlinux.org.uk>,
        Marek =?UTF-8?B?QmVow7pu?= <kabel@kernel.org>,
        Remi Pommarel <repk@triplefau.lt>, Xogium <contact@xogium.me>,
        Tomasz Maciej Nowak <tmn505@gmail.com>,
        linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 17/42] PCI: aardvark: Fix support for MSI interrupts
In-Reply-To: <20210506153153.30454-18-pali@kernel.org>
References: <20210506153153.30454-1-pali@kernel.org>
        <20210506153153.30454-18-pali@kernel.org>
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On Thu, 06 May 2021 16:31:28 +0100,
Pali Rohár <pali@kernel.org> wrote:
> 
> MSI domain callback .alloc (implemented by advk_msi_irq_domain_alloc()
> function) should return zero on success. Returning non-zero value indicates
> failure. Fix return value of this function as in many cases it now returns
> failure while allocating IRQs.
> 
> Aardvark hardware supports Multi-MSI and MSI_FLAG_MULTI_PCI_MSI is already
> set. But when allocating MSI interrupt numbers for Multi-MSI, they need to
> be properly aligned, otherwise endpoint devices send MSI interrupt with
> incorrect numbers. Fix this issue by using function bitmap_find_free_region()
> instead of bitmap_find_next_zero_area().
> 
> To ensure that aligned MSI interrupt numbers are used by endpoint devices,
> we cannot use Linux virtual irq numbers (as they are random and not
> properly aligned). So use hwirq numbers allocated by the function
> bitmap_find_free_region(), which are aligned. This needs an update in
> advk_msi_irq_compose_msi_msg() and advk_pcie_handle_msi() functions to do
> proper mapping between Linux virtual irq numbers and hwirq MSI inner domain
> numbers.
> 
> Also the whole 16-bit MSI number is stored in the PCIE_MSI_PAYLOAD_REG
> register, not only lower 8 bits. Fix reading content of this register.
> 
> This change fixes receiving MSI interrupts on Armada 3720 boards and allows
> using NVMe disks which use Multi-MSI feature with 3 interrupts.
> 
> Without this change, NVMe disks just freeze booting Linux on Armada 3720
> boards as linux nvme-core.c driver is waiting 60s for an interrupt.
> 
> Signed-off-by: Pali Rohár <pali@kernel.org>
> Reviewed-by: Marek Behún <kabel@kernel.org>
> Cc: stable@vger.kernel.org # f21a8b1b6837 ("PCI: aardvark: Move to MSI handling using generic MSI support")
> ---
>  drivers/pci/controller/pci-aardvark.c | 32 ++++++++++++++++-----------
>  1 file changed, 19 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
> index 366d7480bc1b..498810c00b6d 100644
> --- a/drivers/pci/controller/pci-aardvark.c
> +++ b/drivers/pci/controller/pci-aardvark.c
> @@ -118,6 +118,7 @@
>  #define PCIE_MSI_STATUS_REG			(CONTROL_BASE_ADDR + 0x58)
>  #define PCIE_MSI_MASK_REG			(CONTROL_BASE_ADDR + 0x5C)
>  #define PCIE_MSI_PAYLOAD_REG			(CONTROL_BASE_ADDR + 0x9C)
> +#define     PCIE_MSI_DATA_MASK			GENMASK(15, 0)

See my comment below about this addition.

>  /* LMI registers base address and register offsets */
>  #define LMI_BASE_ADDR				0x6000
> @@ -861,7 +862,7 @@ static void advk_msi_irq_compose_msi_msg(struct irq_data *data,
>  
>  	msg->address_lo = lower_32_bits(msi_msg);
>  	msg->address_hi = upper_32_bits(msi_msg);
> -	msg->data = data->irq;
> +	msg->data = data->hwirq;
>  }
>  
>  static int advk_msi_set_affinity(struct irq_data *irq_data,
> @@ -878,15 +879,11 @@ static int advk_msi_irq_domain_alloc(struct irq_domain *domain,
>  	int hwirq, i;
>  
>  	mutex_lock(&pcie->msi_used_lock);
> -	hwirq = bitmap_find_next_zero_area(pcie->msi_used, MSI_IRQ_NUM,
> -					   0, nr_irqs, 0);
> -	if (hwirq >= MSI_IRQ_NUM) {
> -		mutex_unlock(&pcie->msi_used_lock);
> -		return -ENOSPC;
> -	}
> -
> -	bitmap_set(pcie->msi_used, hwirq, nr_irqs);
> +	hwirq = bitmap_find_free_region(pcie->msi_used, MSI_IRQ_NUM,
> +					order_base_2(nr_irqs));
>  	mutex_unlock(&pcie->msi_used_lock);
> +	if (hwirq < 0)
> +		return -ENOSPC;
>  
>  	for (i = 0; i < nr_irqs; i++)
>  		irq_domain_set_info(domain, virq + i, hwirq + i,
> @@ -894,7 +891,7 @@ static int advk_msi_irq_domain_alloc(struct irq_domain *domain,
>  				    domain->host_data, handle_simple_irq,
>  				    NULL, NULL);
>  
> -	return hwirq;
> +	return 0;
>  }
>  
>  static void advk_msi_irq_domain_free(struct irq_domain *domain,
> @@ -904,7 +901,7 @@ static void advk_msi_irq_domain_free(struct irq_domain *domain,
>  	struct advk_pcie *pcie = domain->host_data;
>  
>  	mutex_lock(&pcie->msi_used_lock);
> -	bitmap_clear(pcie->msi_used, d->hwirq, nr_irqs);
> +	bitmap_release_region(pcie->msi_used, d->hwirq, order_base_2(nr_irqs));
>  	mutex_unlock(&pcie->msi_used_lock);
>  }
>  
> @@ -1048,6 +1045,7 @@ static void advk_pcie_handle_msi(struct advk_pcie *pcie)
>  {
>  	u32 msi_val, msi_mask, msi_status, msi_idx;
>  	u16 msi_data;
> +	int virq;
>  
>  	msi_mask = advk_readl(pcie, PCIE_MSI_MASK_REG);
>  	msi_val = advk_readl(pcie, PCIE_MSI_STATUS_REG);
> @@ -1057,9 +1055,17 @@ static void advk_pcie_handle_msi(struct advk_pcie *pcie)
>  		if (!(BIT(msi_idx) & msi_status))
>  			continue;
>  
> +		/*
> +		 * msi_idx contains bits [4:0] of the msi_data and msi_data
> +		 * contains 16bit MSI interrupt number from MSI inner domain
> +		 */
>  		advk_writel(pcie, BIT(msi_idx), PCIE_MSI_STATUS_REG);
> -		msi_data = advk_readl(pcie, PCIE_MSI_PAYLOAD_REG) & 0xFF;
> -		generic_handle_irq(msi_data);
> +		msi_data = advk_readl(pcie, PCIE_MSI_PAYLOAD_REG) & PCIE_MSI_DATA_MASK;

Can this be moved to a separate patch? It seems like this patch should
only focus on correctly dealing with the irq/hwirq issues.

> +		virq = irq_find_mapping(pcie->msi_inner_domain, msi_data);
> +		if (virq)
> +			generic_handle_irq(virq);
> +		else
> +			dev_err(&pcie->pdev->dev, "unexpected MSI 0x%04hx\n", msi_data);

Same concern about the unmitigated screaming.

Thanks,

	M.

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