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Date:   Tue, 12 Jan 2021 08:16:15 +0800
From:   Xu Yilun <yilun.xu@...el.com>
To:     Tom Rix <trix@...hat.com>
Cc:     Moritz Fischer <mdf@...nel.org>, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        lgoncalv@...hat.com, hao.wu@...el.com, yilun.xu@...el.com
Subject: Re: [PATCH v5 1/2] fpga: dfl: add the userspace I/O device support
  for DFL devices

On Mon, Jan 11, 2021 at 06:59:10AM -0800, Tom Rix wrote:
> 
> On 1/10/21 10:16 PM, Xu Yilun wrote:
> > On Sun, Jan 10, 2021 at 12:11:17PM -0800, Moritz Fischer wrote:
> >> On Sat, Jan 02, 2021 at 11:13:01AM +0800, Xu Yilun wrote:
> >>> This patch supports the DFL drivers be written in userspace. This is
> >>> realized by exposing the userspace I/O device interfaces.
> >>>
> >>> The driver leverages the uio_pdrv_genirq, it adds the uio_pdrv_genirq
> >>> platform device with the DFL device's resources, and let the generic UIO
> >>> platform device driver provide support to userspace access to kernel
> >>> interrupts and memory locations.
> >>>
> >>> The driver now supports the ether group feature. To support a new DFL
> >>> feature been directly accessed via UIO, its feature id should be added to
> >>> the driver's id_table.
> >>>
> >>> Signed-off-by: Xu Yilun <yilun.xu@...el.com>
> >>> Reviewed-by: Tom Rix <trix@...hat.com>
> >>> ---
> >>> v2: switch to the new matching algorithem. It matches DFL devices which
> >>>      could not be handled by other DFL drivers.
> >>>     refacor the code about device resources filling.
> >>>     fix some comments.
> >>> v3: split the dfl.c changes out of this patch.
> >>>     some minor fixes
> >>> v4: drop the idea of a generic matching algorithem, instead we specify
> >>>      each matching device in id_table.
> >>>     to make clear that only one irq is supported, the irq handling code
> >>>      is refactored.
> >>> v5: refactor the irq resource code.
> >>> ---
> >>>  drivers/fpga/Kconfig        | 10 +++++
> >>>  drivers/fpga/Makefile       |  1 +
> >>>  drivers/fpga/dfl-uio-pdev.c | 91 +++++++++++++++++++++++++++++++++++++++++++++
> >>>  3 files changed, 102 insertions(+)
> >>>  create mode 100644 drivers/fpga/dfl-uio-pdev.c
> >>>
> >>> diff --git a/drivers/fpga/Kconfig b/drivers/fpga/Kconfig
> >>> index 5ff9438..61445be 100644
> >>> --- a/drivers/fpga/Kconfig
> >>> +++ b/drivers/fpga/Kconfig
> >>> @@ -203,6 +203,16 @@ config FPGA_DFL_NIOS_INTEL_PAC_N3000
> >>>  	  the card. It also instantiates the SPI master (spi-altera) for
> >>>  	  the card's BMC (Board Management Controller).
> >>>  
> >>> +config FPGA_DFL_UIO_PDEV
> >>> +	tristate "FPGA DFL Driver for Userspace I/O platform devices"
> >>> +	depends on FPGA_DFL && UIO_PDRV_GENIRQ
> >>> +	help
> >>> +	  Enable this to allow some DFL drivers be written in userspace. It
> >>> +	  adds the uio_pdrv_genirq platform device with the DFL feature's
> >>> +	  resources, and lets the generic UIO platform device driver provide
> >>> +	  support for userspace access to kernel interrupts and memory
> >>> +	  locations.
> >>> +
> >>>  config FPGA_DFL_PCI
> >>>  	tristate "FPGA DFL PCIe Device Driver"
> >>>  	depends on PCI && FPGA_DFL
> >>> diff --git a/drivers/fpga/Makefile b/drivers/fpga/Makefile
> >>> index 18dc9885..8847fe0 100644
> >>> --- a/drivers/fpga/Makefile
> >>> +++ b/drivers/fpga/Makefile
> >>> @@ -45,6 +45,7 @@ dfl-afu-objs := dfl-afu-main.o dfl-afu-region.o dfl-afu-dma-region.o
> >>>  dfl-afu-objs += dfl-afu-error.o
> >>>  
> >>>  obj-$(CONFIG_FPGA_DFL_NIOS_INTEL_PAC_N3000)	+= dfl-n3000-nios.o
> >>> +obj-$(CONFIG_FPGA_DFL_UIO_PDEV)		+= dfl-uio-pdev.o
> >>>  
> >>>  # Drivers for FPGAs which implement DFL
> >>>  obj-$(CONFIG_FPGA_DFL_PCI)		+= dfl-pci.o
> >>> diff --git a/drivers/fpga/dfl-uio-pdev.c b/drivers/fpga/dfl-uio-pdev.c
> >>> new file mode 100644
> >>> index 0000000..a4cd581
> >>> --- /dev/null
> >>> +++ b/drivers/fpga/dfl-uio-pdev.c
> >>> @@ -0,0 +1,91 @@
> >>> +// SPDX-License-Identifier: GPL-2.0
> >>> +/*
> >>> + * DFL driver for Userspace I/O platform devices
> >>> + *
> >>> + * Copyright (C) 2020 Intel Corporation, Inc.
> >>> + */
> >>> +#include <linux/dfl.h>
> >>> +#include <linux/errno.h>
> >>> +#include <linux/kernel.h>
> >>> +#include <linux/module.h>
> >>> +#include <linux/platform_device.h>
> >>> +#include <linux/slab.h>
> >>> +#include <linux/uio_driver.h>
> >>> +
> >>> +#define DRIVER_NAME "dfl-uio-pdev"
> >>> +
> >>> +static int dfl_uio_pdev_probe(struct dfl_device *ddev)
> >>> +{
> >>> +	struct platform_device_info pdevinfo = { 0 };
> >>> +	struct uio_info uio_pdata = { 0 };
> >>> +	struct platform_device *uio_pdev;
> >>> +	struct device *dev = &ddev->dev;
> >>> +	unsigned int num_res = 1;
> >>> +	struct resource res[2];
> >>> +
> >>> +	res[0].parent = &ddev->mmio_res;
> >>> +	res[0].flags = IORESOURCE_MEM;
> >>> +	res[0].start = ddev->mmio_res.start;
> >>> +	res[0].end = ddev->mmio_res.end;
> >>> +
> >>> +	if (ddev->num_irqs) {
> >>> +		if (ddev->num_irqs > 1)
> >>> +			dev_warn(&ddev->dev,
> >>> +				 "%d irqs for %s, but UIO only supports the first one\n",
> >>> +				 ddev->num_irqs, dev_name(&ddev->dev));
> >>> +
> >>> +		res[1].flags = IORESOURCE_IRQ;
> >>> +		res[1].start = ddev->irqs[0];
> >>> +		res[1].end = ddev->irqs[0];
> >>> +		num_res++;
> >>> +	}
> >>> +
> >>> +	uio_pdata.name = DRIVER_NAME;
> >>> +	uio_pdata.version = "0";
> >>> +
> >>> +	pdevinfo.name = "uio_pdrv_genirq";
> >>> +	pdevinfo.res = res;
> >>> +	pdevinfo.num_res = num_res;
> >>> +	pdevinfo.parent = &ddev->dev;
> >>> +	pdevinfo.id = PLATFORM_DEVID_AUTO;
> >>> +	pdevinfo.data = &uio_pdata;
> >>> +	pdevinfo.size_data = sizeof(uio_pdata);
> >>> +
> >>> +	uio_pdev = platform_device_register_full(&pdevinfo);
> >>> +	if (!IS_ERR(uio_pdev))
> >>> +		dev_set_drvdata(dev, uio_pdev);
> >> I'm not sure if this is more readable than:
> >>
> >>    	uio_pdev = platform_device_register_full(&pdevinfo);
> >>    	if (IS_ERR(uio_pdev))
> >>    		return PTR_ERR(uio_pdev);
> >>
> >> 	dev_set_drvdata(dev, uio_pdev);
> >> 	return 0;
> >>
> >> No strong preference, though ... :)
> > I think your version is more readable, I'll change it.
> >
> >>> +
> >>> +	return PTR_ERR_OR_ZERO(uio_pdev);
> >>> +}
> >>> +
> >>> +static void dfl_uio_pdev_remove(struct dfl_device *ddev)
> >>> +{
> >>> +	struct platform_device *uio_pdev = dev_get_drvdata(&ddev->dev);
> >>> +
> >>> +	platform_device_unregister(uio_pdev);
> >>> +}
> >>> +
> >>> +#define FME_FEATURE_ID_ETH_GROUP	0x10
> >>> +
> >>> +static const struct dfl_device_id dfl_uio_pdev_ids[] = {
> >>> +	{ FME_ID, FME_FEATURE_ID_ETH_GROUP },
> >> Will you want to always bind FME_FEATURE_ID_ETH_GROUP? If not I'd suggest not
> >> to add it here.
> > Actually this is not the most preferable to me. I'm always looking for a
> > generic way to bind the uio driver to user assigned dfl devices. But there
> > is concern that userspace should not be responsible for the device driver
> > matching in previous mail thread:
> >
> > https://lore.kernel.org/linux-fpga/1602828151-24784-2-git-send-email-yilun.xu@intel.com/
> >
> > But TBH I still didn't figure out why driver_override is not OK in this
> > case.
> >
> >> If you want to provide an option to somewhat non-ABI fixed bind things
> >> you could look at what vfio-pci does (provide a module parameter),
> >> otherwise use sysfs 'new_id' or 'bind'.
> > I would like to have a "new_id" for dfl bus driver. It is not generic to
> > all drivers, I need to add the attr for dfl drivers like pci do.
> >
> > My concern is how the module param or "new_id" is different from
> > "driver_override", seems userspace is also taking part in the device
> > matching.
> >
> > But since we've restarted the discussion, I'm very much willing to have
> > a try on the "new_id".
> 
> I don't believe there is any problem with the basic platform uio driver.
> 
> Can we split it out and work the new_id change in parallel ?

Yes. The Ether Group is always bind to the uio driver for Intel PAC
N3000. So this patch works properly now. We could have a separate patch
for the new_id.

Thanks,
Yilun

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