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

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Message-ID: <8520D5D51A55D047800579B0941471982585CBDA@XAP-PVEXMBX01.xlnx.xilinx.com>
Date:	Tue, 17 Nov 2015 04:59:39 +0000
From:	Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>
To:	Ray Jui <rjui@...adcom.com>, Marc Zyngier <marc.zyngier@....com>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"pawel.moll@....com" <pawel.moll@....com>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"galak@...eaurora.org" <galak@...eaurora.org>,
	Michal Simek <michals@...inx.com>,
	Soren Brinkmann <sorenb@...inx.com>,
	"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	"arnd@...db.de" <arnd@...db.de>,
	"tinamdar@....com" <tinamdar@....com>,
	"treding@...dia.com" <treding@...dia.com>,
	"Minghuan.Lian@...escale.com" <Minghuan.Lian@...escale.com>,
	"m-karicheri2@...com" <m-karicheri2@...com>,
	"hauke@...ke-m.de" <hauke@...ke-m.de>,
	"dhdang@....com" <dhdang@....com>,
	"sbranden@...adcom.com" <sbranden@...adcom.com>
CC:	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Ravikiran Gummaluri <rgummal@...inx.com>
Subject: RE: [PATCH v8] PCI: Xilinx-NWL-PCIe: Added support for Xilinx NWL
 PCIe Host Controller

> On 11/16/2015 7:14 AM, Marc Zyngier wrote:
> > On 11/11/15 06:33, Bharat Kumar Gogada 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
> >>
> >
> > [...]
> >
> >> +static int nwl_pcie_enable_msi(struct nwl_pcie *pcie, struct pci_bus
> >> +*bus) {
> >> +	struct platform_device *pdev = to_platform_device(pcie->dev);
> >> +	struct nwl_msi *msi = &pcie->msi;
> >> +	unsigned long base;
> >> +	int ret;
> >> +
> >> +	mutex_init(&msi->lock);
> >> +
> >> +	/* Check for msii_present bit */
> >> +	ret = nwl_bridge_readl(pcie, I_MSII_CAPABILITIES) & MSII_PRESENT;
> >> +	if (!ret) {
> >> +		dev_err(pcie->dev, "MSI not present\n");
> >> +		ret = -EIO;
> >> +		goto err;
> >> +	}
> >> +
> >> +	/* Enable MSII */
> >> +	nwl_bridge_writel(pcie, nwl_bridge_readl(pcie, I_MSII_CONTROL) |
> >> +			  MSII_ENABLE, I_MSII_CONTROL);
> >> +
> >> +	/* Enable MSII status */
> >> +	nwl_bridge_writel(pcie, nwl_bridge_readl(pcie, I_MSII_CONTROL) |
> >> +			  MSII_STATUS_ENABLE, I_MSII_CONTROL);
> >> +
> >> +	/* setup AFI/FPCI range */
> >> +	msi->pages = __get_free_pages(GFP_KERNEL, 0);
> >> +	base = virt_to_phys((void *)msi->pages);
> >> +	nwl_bridge_writel(pcie, lower_32_bits(base), I_MSII_BASE_LO);
> >> +	nwl_bridge_writel(pcie, upper_32_bits(base), I_MSII_BASE_HI);
> >
> > BTW, you still haven't answered my question as to why you need to
> > waste a page of memory here, and why putting a device address doesn't
> work.
> >
> > As this is (to the best of my knowledge) the only driver doing so, I'd
> > really like you to explain the rational behind this.
> 
> Might not be the only driver doing so after I start sending out patches for the
> iProc MSI support (soon), :)
> 
> I'm not sure how it works for the Xilinx NWL controller, which Bharat should
> be able to help to explain. But for the iProc MSI controller, there's no device
> I/O memory reserved for MSI posted writes in the ASIC.
> Therefore one needs to reserve host memory for these writes.
> >

Our SoC doesn't reserve any memory for MSI, hence we need to assign a memory space for it out of RAM.

Regards,
Bharat


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