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

[Alan Tull]

On Wed, May 23, 2018 at 10:28 AM, Wu Hao <hao.wu@xxxxxxxxx> 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@xxxxxxxxx> 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@xxxxxxxxx>
>> > Signed-off-by: Enno Luebbers <enno.luebbers@xxxxxxxxx>
>> > Signed-off-by: Shiva Rao <shiva.rao@xxxxxxxxx>
>> > Signed-off-by: Christopher Rauer <christopher.rauer@xxxxxxxxx>
>> > Signed-off-by: Wu Hao <hao.wu@xxxxxxxxx>
>> > Acked-by: Alan Tull <atull@xxxxxxxxxx>
>> > Acked-by: Moritz Fischer <mdf@xxxxxxxxxx>
>> > ---
>> > 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@xxxxxxxxx>
>> > + *   Joseph Grecco <joe.grecco@xxxxxxxxx>
>> > + *   Enno Luebbers <enno.luebbers@xxxxxxxxx>
>> > + *   Tim Whisonant <tim.whisonant@xxxxxxxxx>
>> > + *   Ananda Ravuri <ananda.ravuri@xxxxxxxxx>
>> > + *   Henry Mitchel <henry.mitchel@xxxxxxxxx>
>> > + */
>> > +
>> > +#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.

[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.

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
>> >