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Date: Tue, 17 Nov 2015 08:24:47 -0800
From: Ray Jui <rjui@...adcom.com>
To: Marc Zyngier <marc.zyngier@....com>,
Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>
CC: "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>,
"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>,
Robin Murphy <Robin.Murphy@....com>
Subject: Re: [PATCH v8] PCI: Xilinx-NWL-PCIe: Added support for Xilinx NWL
PCIe Host Controller
On 11/17/2015 5:55 AM, Marc Zyngier wrote:
> On 17/11/15 13:27, Bharat Kumar Gogada wrote:
>>>
>>> On Tue, 17 Nov 2015 04:59:39 +0000
>>> Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com> wrote:
>>>
>>>>> 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.
>>>
>>> Question to both of you: Does the write make it to memory? Or is it sampled
>>> by the bridge and dropped?
>>>
>> No, write will not do any modification in memory, it is consumed by bridge.
>
> Then you do not need to allocate memory at all. Use whatever memory you
> already have. CC-ing Robin, as this may have interaction with the SMMU.
>
>>
>>> What happens if you replace the page in RAM with a dummy address?
>> What do you mean by dummy address ?
>
> Any random (and suitably aligned) address. 0x00000deadbeef000 for example.
In our case, I'm pretty sure the writes make it to memory (RAM). I can
try replacing it with a dummy address, but I'm pretty sure that will not
work.
Thanks,
Ray
>
> Thanks,
>
> M.
>
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