Re: [PATCH v5 20/28] fpga: dfl: add fpga bridge platform driver for FME

Alan Tull
2018-05-24T17:26:09Z

On Wed, May 23, 2018 at 6:42 PM, Wu Hao <hao.wu@intel.com> wrote:
> On Wed, May 23, 2018 at 04:06:17PM -0500, Alan Tull wrote:
>> On Wed, May 23, 2018 at 10:28 AM, Wu Hao <hao.wu@intel.com> wrote:
>> > On Wed, May 23, 2018 at 10:15:00AM -0500, Alan Tull wrote:
>> >> On Tue, May 1, 2018 at 9:50 PM, Wu Hao <hao.wu@intel.com> wrote:
>> >>
>> >> Hi Hao,
>> >>
>> >> > This patch adds fpga bridge platform driver for FPGA Management Engine.
>> >> > It implements the enable_set callback for fpga bridge.
>> >> >
>> >> > Signed-off-by: Tim Whisonant <tim.whisonant@intel.com>
>> >> > Signed-off-by: Enno Luebbers <enno.luebbers@intel.com>
>> >> > Signed-off-by: Shiva Rao <shiva.rao@intel.com>
>> >> > Signed-off-by: Christopher Rauer <christopher.rauer@intel.com>
>> >> > Signed-off-by: Wu Hao <hao.wu@intel.com>
>> >> > Acked-by: Alan Tull <atull@kernel.org>
>> >> > Acked-by: Moritz Fischer <mdf@kernel.org>
>> >> > ---
>> >> > v3: rename driver to fpga-dfl-fme-br
>> >> > remove useless dev_dbg in probe function.
>> >> > rebased due to fpga api change.
>> >> > v4: rename to dfl-fme-br and fix SPDX license issue
>> >> > include dfl-fme-pr.h instead of dfl-fme.h
>> >> > add Acked-by from Alan and Moritz
>> >> > v5: rebase due to API changes.
>> >> > defer port and its ops finding when really need.
>> >> > ---
>> >> > drivers/fpga/Kconfig | 6 +++
>> >> > drivers/fpga/Makefile | 1 +
>> >> > drivers/fpga/dfl-fme-br.c | 114 ++++++++++++++++++++++++++++++++++++++++++++++
>> >> > 3 files changed, 121 insertions(+)
>> >> > create mode 100644 drivers/fpga/dfl-fme-br.c
>> >> >
>> >> > diff --git a/drivers/fpga/Kconfig b/drivers/fpga/Kconfig
>> >> > index 89f76e8..a8f939a 100644
>> >> > --- a/drivers/fpga/Kconfig
>> >> > +++ b/drivers/fpga/Kconfig
>> >> > @@ -156,6 +156,12 @@ config FPGA_DFL_FME_MGR
>> >> > help
>> >> > Say Y to enable FPGA Manager driver for FPGA Management Engine.
>> >> >
>> >> > +config FPGA_DFL_FME_BRIDGE
>> >> > + tristate "FPGA DFL FME Bridge Driver"
>> >> > + depends on FPGA_DFL_FME
>> >> > + help
>> >> > + Say Y to enable FPGA Bridge driver for FPGA Management Engine.
>> >> > +
>> >> > config FPGA_DFL_PCI
>> >> > tristate "FPGA Device Feature List (DFL) PCIe Device Driver"
>> >> > depends on PCI && FPGA_DFL
>> >> > diff --git a/drivers/fpga/Makefile b/drivers/fpga/Makefile
>> >> > index f82814a..75096e9 100644
>> >> > --- a/drivers/fpga/Makefile
>> >> > +++ b/drivers/fpga/Makefile
>> >> > @@ -32,6 +32,7 @@ obj-$(CONFIG_OF_FPGA_REGION) += of-fpga-region.o
>> >> > obj-$(CONFIG_FPGA_DFL) += dfl.o
>> >> > obj-$(CONFIG_FPGA_DFL_FME) += dfl-fme.o
>> >> > obj-$(CONFIG_FPGA_DFL_FME_MGR) += dfl-fme-mgr.o
>> >> > +obj-$(CONFIG_FPGA_DFL_FME_BRIDGE) += dfl-fme-br.o
>> >> >
>> >> > dfl-fme-objs := dfl-fme-main.o dfl-fme-pr.o
>> >> >
>> >> > diff --git a/drivers/fpga/dfl-fme-br.c b/drivers/fpga/dfl-fme-br.c
>> >> > new file mode 100644
>> >> > index 0000000..5c51b08
>> >> > --- /dev/null
>> >> > +++ b/drivers/fpga/dfl-fme-br.c
>> >> > @@ -0,0 +1,114 @@
>> >> > +// SPDX-License-Identifier: GPL-2.0
>> >> > +/*
>> >> > + * FPGA Bridge Driver for FPGA Management Engine (FME)
>> >> > + *
>> >> > + * Copyright (C) 2017 Intel Corporation, Inc.
>> >> > + *
>> >> > + * Authors:
>> >> > + * Wu Hao <hao.wu@intel.com>
>> >> > + * Joseph Grecco <joe.grecco@intel.com>
>> >> > + * Enno Luebbers <enno.luebbers@intel.com>
>> >> > + * Tim Whisonant <tim.whisonant@intel.com>
>> >> > + * Ananda Ravuri <ananda.ravuri@intel.com>
>> >> > + * Henry Mitchel <henry.mitchel@intel.com>
>> >> > + */
>> >> > +
>> >> > +#include <linux/module.h>
>> >> > +#include <linux/fpga/fpga-bridge.h>
>> >> > +
>> >> > +#include "dfl.h"
>> >> > +#include "dfl-fme-pr.h"
>> >> > +
>> >> > +struct fme_br_priv {
>> >> > + struct dfl_fme_br_pdata *pdata;
>> >> > + struct dfl_fpga_port_ops *port_ops;
>> >> > + struct platform_device *port_pdev;
>> >> > +};
>> >> > +
>> >> > +static int fme_bridge_enable_set(struct fpga_bridge *bridge, bool enable)
>> >> > +{
>> >> > + struct fme_br_priv *priv = bridge->priv;
>> >> > + struct platform_device *port_pdev;
>> >> > + struct dfl_fpga_port_ops *ops;
>> >> > +
>> >> > + if (!priv->port_pdev) {
>> >> > + port_pdev = dfl_fpga_cdev_find_port(priv->pdata->cdev,
>> >> > + &priv->pdata->port_id,
>> >> > + dfl_fpga_check_port_id);
>> >> > + if (!port_pdev)
>> >> > + return -ENODEV;
>> >> > +
>> >> > + priv->port_pdev = port_pdev;
>> >> > + }
>> >> > +
>> >> > + if (priv->port_pdev && !priv->port_ops) {
>> >> > + ops = dfl_fpga_get_port_ops(priv->port_pdev);
>> >> > + if (!ops || !ops->enable_set)
>> >> > + return -ENOENT;
>> >> > +
>> >> > + priv->port_ops = ops;
>> >> > + }
>> >>
>> >> This is saving some pointers. Is it possible that the port_pdev or
>> >> port_ops could go away?
>> >
>> > Hi Alan
>> >
>> > Thanks for the comments.
>> >
>> > The find_port function will get the port device to prevent that.
>> > You can see put device in remove function. And it's similar for the
>> > port ops. In dfl_fpga_get_port_ops function, it will prevent unexpected
>> > port ops removing by try module get.
>>
>> OK, good, and I see the find_port function documents that put_device
>> is needed, so that's good too.
>>
>> When we previously discussed this [1] you described a procedure of
>> hot-unplugging the VF AFU from the VM and turning it back to PF before
>> doing the FPGA programming. Some comments on that would be helpful,
>> maybe located with the port_ops functions.
>>
>
> Hi Alan
>
> Actually I plan to add those descriptions about virtualization in the
> documenation/fpga/dfl.txt, together with the patch which enables the
> virtualization support for Intel FPGA device (e.g Intel PAC card).

Great

> I
> think dfl.txt is a better place to have that procedure documented.
> How do you think?

If it is only in the dff.txt, it may remain unclear (in the code) that
that is an issue that the code is working around.

>
>
>> [1] https://lkml.org/lkml/2018/4/6/180
>>
>> >
>> >>
>> >> Also, the port ops routines probably should be named
>> >> dfl_fpga_port_ops_get/find_port/etc
>> >>
>> >
>> > Hm.. as I see there are functions named as get_device(), put_device(), so
>> > I just name it as ..._get_port_ops and ..._put_port_ops in similar way. :)
>> > If you think that could be a better name, it's fine for me to change them.
>>
>> Yes, I've seen that too. I think keeping the prefix the same helps to
>> organize the namespace. Plus :) if I'm grepping through the code, I
>> can be lazy and not have to use a regex to find the port ops
>> functions.
>
> so we good with current naming?

Recently GregKH give us some guidance about using a common prefix [2].

>
> some places we find it's get_device() and put_device(), but other functions
> like device_add(), device_del(). actually it's not a big problem I think, :)
> currently port_ops has a unified style ..._add/del/get/put_port_ops. I am
> fine with both kind of naming, if you prefer ...port_ops_add/del/get/put
> style, please let me know, I can change them in the next version.

Since you have struct dfl_fpga_port_ops, you can just add _{action} to
the name of the struct and you have dfl_fpga_port_ops_add/del/get/pu

Thanks,
Alan

[2] https://lkml.org/lkml/2018/3/15/709

>
> Thanks
> Hao
>
>>
>> Alan
>>
>> >
>> > Thanks
>> > Hao
>> >
>> >> Alan
>> >>
>> >> > +
>> >> > + return priv->port_ops->enable_set(priv->port_pdev, enable);
>> >> > +}
>> >> > +
>> >> > +static const struct fpga_bridge_ops fme_bridge_ops = {
>> >> > + .enable_set = fme_bridge_enable_set,
>> >> > +};
>> >> > +
>> >> > +static int fme_br_probe(struct platform_device *pdev)
>> >> > +{
>> >> > + struct device *dev = &pdev->dev;
>> >> > + struct fme_br_priv *priv;
>> >> > + struct fpga_bridge *br;
>> >> > + int ret;
>> >> > +
>> >> > + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>> >> > + if (!priv)
>> >> > + return -ENOMEM;
>> >> > +
>> >> > + priv->pdata = dev_get_platdata(dev);
>> >> > +
>> >> > + br = fpga_bridge_create(dev, "DFL FPGA FME Bridge",
>> >> > + &fme_bridge_ops, priv);
>> >> > + if (!br)
>> >> > + return -ENOMEM;
>> >> > +
>> >> > + platform_set_drvdata(pdev, br);
>> >> > +
>> >> > + ret = fpga_bridge_register(br);
>> >> > + if (ret)
>> >> > + fpga_bridge_free(br);
>> >> > +
>> >> > + return ret;
>> >> > +}
>> >> > +
>> >> > +static int fme_br_remove(struct platform_device *pdev)
>> >> > +{
>> >> > + struct fpga_bridge *br = platform_get_drvdata(pdev);
>> >> > + struct fme_br_priv *priv = br->priv;
>> >> > +
>> >> > + fpga_bridge_unregister(br);
>> >> > +
>> >> > + if (priv->port_pdev)
>> >> > + put_device(&priv->port_pdev->dev);
>> >> > + if (priv->port_ops)
>> >> > + dfl_fpga_put_port_ops(priv->port_ops);
>> >> > +
>> >> > + return 0;
>> >> > +}
>> >> > +
>> >> > +static struct platform_driver fme_br_driver = {
>> >> > + .driver = {
>> >> > + .name = DFL_FPGA_FME_BRIDGE,
>> >> > + },
>> >> > + .probe = fme_br_probe,
>> >> > + .remove = fme_br_remove,
>> >> > +};
>> >> > +
>> >> > +module_platform_driver(fme_br_driver);
>> >> > +
>> >> > +MODULE_DESCRIPTION("FPGA Bridge for DFL FPGA Management Engine");
>> >> > +MODULE_AUTHOR("Intel Corporation");
>> >> > +MODULE_LICENSE("GPL v2");
>> >> > +MODULE_ALIAS("platform:dfl-fme-bridge");
>> >> > --
>> >> > 1.8.3.1
>> >> >
>> --
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