linux-kernel - Re: [PATCH v8] PCI: Xilinx-NWL-PCIe: Added support for Xilinx NWL PCIe Host Controller

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Date:	Wed, 11 Nov 2015 17:37:12 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>
Cc:	<robh+dt@...nel.org>, <pawel.moll@....com>, <mark.rutland@....com>,
	<ijc+devicetree@...lion.org.uk>, <galak@...eaurora.org>,
	<michals@...inx.com>, <sorenb@...inx.com>, <bhelgaas@...gle.com>,
	<arnd@...db.de>, <tinamdar@....com>, <treding@...dia.com>,
	<rjui@...adcom.com>, <Minghuan.Lian@...escale.com>,
	<m-karicheri2@...com>, <hauke@...ke-m.de>, <dhdang@....com>,
	<sbranden@...adcom.com>, <devicetree@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>,
	"Bharat Kumar Gogada" <bharatku@...inx.com>,
	Ravi Kiran Gummaluri <rgummal@...inx.com>
Subject: Re: [PATCH v8] PCI: Xilinx-NWL-PCIe: Added support for Xilinx NWL
 PCIe Host Controller

On Wed, 11 Nov 2015 12:03:39 +0530
Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com> wrote:

> Adding PCIe Root Port driver for Xilinx PCIe NWL bridge IP.
> 
> Signed-off-by: Bharat Kumar Gogada <bharatku@...inx.com>
> Signed-off-by: Ravi Kiran Gummaluri <rgummal@...inx.com>
> ---
> Added logic to allocate contiguous hwirq in nwl_irq_domain_alloc function.
> Moved MSI functionality to separate functions.
> Changed error return values.
> ---
>  .../devicetree/bindings/pci/xilinx-nwl-pcie.txt    |   68 ++
>  drivers/pci/host/Kconfig                           |   16 +-
>  drivers/pci/host/Makefile                          |    1 +
>  drivers/pci/host/pcie-xilinx-nwl.c                 | 1062 ++++++++++++++++++++
>  4 files changed, 1144 insertions(+), 3 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/pci/xilinx-nwl-pcie.txt
>  create mode 100644 drivers/pci/host/pcie-xilinx-nwl.c
> 
> diff --git a/drivers/pci/host/pcie-xilinx-nwl.c b/drivers/pci/host/pcie-xilinx-nwl.c
> new file mode 100644
> index 0000000..8bc509c
> --- /dev/null
> +++ b/drivers/pci/host/pcie-xilinx-nwl.c

[...]

> +static struct msi_domain_info nwl_msi_domain_info = {
> +	.flags = (MSI_FLAG_USE_DEF_DOM_OPS | MSI_FLAG_USE_DEF_CHIP_OPS |
> +		  MSI_FLAG_MULTI_PCI_MSI),

Given that you claim to support multi-MSI...

[...]

> +static int nwl_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
> +				unsigned int nr_irqs, void *args)
> +{
> +	struct nwl_pcie *pcie = domain->host_data;
> +	struct nwl_msi *msi = &pcie->msi;
> +	unsigned long bit;
> +	int i;
> +
> +	mutex_lock(&msi->lock);
> +	for (i = 0; i < nr_irqs; i++) {
> +		bit = find_first_zero_bit(msi->used, INT_PCI_MSI_NR);
> +		if (bit < INT_PCI_MSI_NR)
> +			set_bit(bit, msi->used);
> +		else
> +			bit = -ENOSPC;
> +
> +		if (bit < 0) {
> +			mutex_unlock(&msi->lock);
> +			return bit;
> +		}
> +
> +		irq_domain_set_info(domain, virq, bit, &nwl_irq_chip,
> +				domain->host_data, handle_simple_irq,
> +				NULL, NULL);
> +		virq = virq + 1;
> +	}

I really don't see how this allocator guarantees that all hwirqs are
contiguous. I already mentioned this when reviewing v7, and you still
haven't got it right. So either you allocate *contiguous* hwirqs in an
atomic fashion, or you drop support for multi-MSI.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny.
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