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SubjectRe: [PATCH v4 14/24] fpga: dfl: fme: add partial reconfiguration sub feature support
On Tue, Mar 06, 2018 at 12:29:35PM -0600, Alan Tull wrote:
> On Mon, Mar 5, 2018 at 8:08 PM, Wu Hao <hao.wu@intel.com> wrote:
> > On Mon, Mar 05, 2018 at 04:46:02PM -0600, Alan Tull wrote:
> >> On Tue, Feb 13, 2018 at 3:24 AM, Wu Hao <hao.wu@intel.com> wrote:
> >>
> >> Hi Hao,
> >
> > Hi Alan,
> >
> > Thanks for the comments.
> >
> >>
> >> We are going to want to be able use different FPGA managers with this
> >> framework. The different manager may be part of a different FME in
> >> fabric or it may be a hardware FPGA manager. Fortunately, at this
> >> point now the changes, noted below, to get there are pretty small.
> >
> > Yes, understand these could be some cases that FME having different PR
> > hardware.
> >
>
> Or supporting reduced FME plus hardware-based FPGA manager.
>
> Just to re-emphasize, the basic intent of the FPGA manager subsystem
> in the first place is to have FPGA managers separate from higher level
> frameworks so that the higher level frameworks will be able to able to
> use different FPGAs.
>
> >> > +/**
> >> > + * fpga_fme_create_mgr - create fpga mgr platform device as child device
> >> > + *
> >> > + * @pdata: fme platform_device's pdata
> >> > + *
> >> > + * Return: mgr platform device if successful, and error code otherwise.
> >> > + */
> >> > +static struct platform_device *
> >> > +fpga_fme_create_mgr(struct feature_platform_data *pdata)
> >> > +{
> >> > + struct platform_device *mgr, *fme = pdata->dev;
> >> > + struct feature *feature;
> >> > + struct resource res;
> >> > + struct resource *pres;
> >> > + int ret = -ENOMEM;
> >> > +
> >> > + feature = get_feature_by_id(&pdata->dev->dev, FME_FEATURE_ID_PR_MGMT);
> >> > + if (!feature)
> >> > + return ERR_PTR(-ENODEV);
> >> > +
> >> > + /*
> >> > + * Each FME has only one fpga-mgr, so allocate platform device using
> >> > + * the same FME platform device id.
> >> > + */
> >> > + mgr = platform_device_alloc(FPGA_DFL_FME_MGR, fme->id);
> >>
> >> At this point, the framework is assuming all FME's include the same
> >> FPGA manager device which would use the driver in dfl-fme-mgr.c.
> >>
> >> I'm thinking of two cases where the manager isn't the same as a
> >> dfl-fme-mgr.c manager are a bit different:
> >>
> >> (1) a FME-based FPGA manager, but different implementation, different
> >> registers. The constraint is that the port implementation has to be
> >> similar enough to use the rest of the base FME code. I am wondering
> >> if the FPGA manager can be added to the DFL. At this point, the DFL
> >> would drive which FPGA manager is alloc'd. That way the user gets to
> >> use all this code in dfl-fme-pr.c but with their FPGA manager.
> >
> > Actually I'm not sure how this will be implemented in the hardware in the
> > future, but from my understanding, there may be several methods to add this
> > support (a different PR hardware) to FME.
> >
> > 1) introduce a new PR sub feature to FME.
> > driver knows it by different feature id, and create different fpga
> > manager platform device, but may not be able to reuse dfl-fme-pr.c.
>
> What would prevent reusing dfl-fme-pr.c? It looks like this is 98% of
> the way there and only needs a way of knowing which FPGA manager
> driver to alloc here. I am hoping that a new PR sub feature could be
> added and that dfl-fme-pr.c can be reused.

It depeneds on how hardware implements it. : )
I agree that if it follows the same way of current PR sub feature, then we
could reuse the dfl-fme-pr.c for sure.

>
> >
> > 2) add a different PR hardware support to current PR sub feature.
> > It requires hardware to add registers to indicate this is a different
> > PR hardware than dfl-fme-mgr.c, and its register region information
> > (e.g location and size). Then this dfl-fme-pr.c driver could read
> > these information from hardware and create a different fpga manager
> > platform device with correct resources.
>
> So this dfl-fme-pr.c would have to know where some ID registers are
> and the enumeration gets messier. Some of the enumeration would be
> DFL and some would be from information that is not in the DFL headers.
> The DFL should contain the knowledge of which mgr to use.

Actually I don't know how hardware will implement this in the future, but I
just listed my ideas here. Per my understanding, driver (reuse dfl-fme-pr.c)
needs some more information to decide which platform device to create (for
fpga manager).

1) introduce a new PR sub feature. Then it has a different private feature
id in DFH (Device Feature Header). driver could use this id to create a
different platform device.

2) introduce some registers inside the current PR sub feature. Then driver
could read these registers to know which platform device to create for fpga
manager.

I think either 1) or 2) will only require small changes to current driver
code, I don't have any concern on supporting different PR hardware. :)

I understand your concern on case 2), everybody who wants to reuse dfl-fme-pr.c
needs to implement ID register which is not defined by DFL, so I guess we
should suggest 1).

>
> >
> > I think current driver framework could support both cases above for sure.
> >
> >>
> >> (2) a FPGA manager that can be added by device tree in the case of a
> >> platform that is using device tree. I think this will be pretty
> >> simple and can be done later when someone is actually bringing this
> >> framework up on a FPGA running under device tree. I'm thinking that
> >> the base DFL device that reads the dfl data from hardware can have a
> >> DT property that points to the FPGA manager. That manager can be
> >> saved somewhere handy like the pdata and passed down to this code,
> >> which realizes it can use that existing device and doesn't need to
> >> alloc a platform device. But again, that's probably best done later.
> >
> > Sure, we can discuss further when we really need it. Actually per my
> > understanding, if hardware describes itself clearly, we may not have to
> > use DT for fpga manager, as driver could create it automatically based
> > on information read from hardware. :)
>
> DT exists for busses that don't have that kind of discovery. For a
> concrete example, consider how the Arria10 driver (socfpga-a10.c)
> probe function is getting its two mmio spaces and clock.

I see. If we have to create fpga mgr using DT some cases, it makes sense
that we just link the existing one instead.

>
> >
> >>
> >> > + if (!mgr)
> >> > + return ERR_PTR(ret);
> >> > +
> >> > + mgr->dev.parent = &fme->dev;
> >> > +
> >> > + pres = platform_get_resource(fme, IORESOURCE_MEM,
> >> > + feature->resource_index);
> >> > + if (!pres) {
> >> > + ret = -ENODEV;
> >> > + goto create_mgr_err;
> >> > + }
> >> > +
> >> > + memset(&res, 0, sizeof(struct resource));
> >> > +
> >> > + res.start = pres->start;
> >> > + res.end = pres->end;
> >> > + res.name = pres->name;
> >> > + res.flags = IORESOURCE_MEM;
> >> > +
> >> > + ret = platform_device_add_resources(mgr, &res, 1);
> >> > + if (ret)
> >> > + goto create_mgr_err;
> >> > +
> >> > + ret = platform_device_add(mgr);
> >> > + if (ret)
> >> > + goto create_mgr_err;
> >> > +
> >> > + return mgr;
> >> > +
> >> > +create_mgr_err:
> >> > + platform_device_put(mgr);
> >> > + return ERR_PTR(ret);
> >> > +}
>
> >> > diff --git a/drivers/fpga/dfl-fme-pr.h b/drivers/fpga/dfl-fme-pr.h
> >> > new file mode 100644
> >> > index 0000000..11bd001
> >> > --- /dev/null
> >> > +++ b/drivers/fpga/dfl-fme-pr.h
> >> > @@ -0,0 +1,113 @@
> >> > +/* SPDX-License-Identifier: GPL-2.0 */
> >> > +/*
> >> > + * Header file for FPGA Management Engine (FME) Partial Reconfiguration Driver
> >> > + *
> >> > + * Copyright (C) 2017 Intel Corporation, Inc.
> >> > + *
> >> > + * Authors:
> >> > + * Kang Luwei <luwei.kang@intel.com>
> >> > + * Xiao Guangrong <guangrong.xiao@linux.intel.com>
> >> > + * 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>
> >> > + */
> >> > +
> >> > +#ifndef __DFL_FME_PR_H
> >> > +#define __DFL_FME_PR_H
> >> > +
> >> > +#include <linux/platform_device.h>
> >> > +
> >> > +/**
> >> > + * struct fme_region - FME fpga region data structure
> >> > + *
> >> > + * @region: platform device of the FPGA region.
> >> > + * @node: used to link fme_region to a list.
> >> > + * @port_id: indicate which port this region connected to.
> >> > + */
> >> > +struct fme_region {
> >> > + struct platform_device *region;
> >> > + struct list_head node;
> >> > + int port_id;
> >> > +};
> >> > +
> >> > +/**
> >> > + * struct fme_region_pdata - platform data for FME region platform device.
> >> > + *
> >> > + * @mgr: platform device of the FPGA manager.
> >> > + * @br: platform device of the FPGA bridge.
> >> > + * @region_id: region id (same as port_id).
> >> > + */
> >> > +struct fme_region_pdata {
> >> > + struct platform_device *mgr;
> >> > + struct platform_device *br;
> >> > + int region_id;
> >> > +};
> >> > +
> >> > +/**
> >> > + * struct fme_bridge - FME fpga bridge data structure
> >> > + *
> >> > + * @br: platform device of the FPGA bridge.
> >> > + * @node: used to link fme_bridge to a list.
> >> > + */
> >> > +struct fme_bridge {
> >> > + struct platform_device *br;
> >> > + struct list_head node;
> >> > +};
> >> > +
> >> > +/**
> >> > + * struct fme_bridge_pdata - platform data for FME bridge platform device.
> >> > + *
> >> > + * @port: platform device of the port feature dev.
> >> > + */
> >> > +struct fme_br_pdata {
> >> > + struct platform_device *port;
> >> > +};
> >> > +
> >> > +#define FPGA_DFL_FME_MGR "dfl-fme-mgr"
> >> > +#define FPGA_DFL_FME_BRIDGE "dfl-fme-bridge"
> >> > +#define FPGA_DFL_FME_REGION "dfl-fme-region"
> >> > +
> >> Everything in dfl-fme-pr.h up to this point is good and general and
> >> should remain in dfl-fme-pr.h. The register #defines for this FME's
> >> FPGA manager device below should be associated with the FPGA manager
> >> driver. Sorry if the way I stated that in the v3 review wasn't clear.
> >
> > Actually I put the PR sub feature register set definitions in this header
> > file (dfl-fme-pr.h), because it's possible the driver (dfl-fme-pr.c) of
> > this PR sub feature access some of the registers in the future. e.g read
> > some PR sub feature registers to create different fpga manager platform
> > devices as I mentioned above.
>
> That sounds like a workaround. Since you're adding a new method of
> enumeration, you should use that new method of enumeration to choose
> which FPGA manager is being used. Otherwise we are ending up with
> multi-level enumeration, i.e. look at the DFL and then look at a
> specific register location in the device.
>
> >
> > I have to say this is only future consideration, and in this dfl-fme-pr.c
> > driver there is no code to access below registers currently. I can move all
> > of them to dfl-fme-mgr.h or dfl-fme-mgr.c in the next version if this is
> > preferred. : )
>
> That sounds good. That makes the mgr driver its own separate thing
> which is what is supposed to happen in this framework.

Sure, will fix this.

Thanks
Hao

>
> >
> >>
> >> > +/* FME Partial Reconfiguration Sub Feature Register Set */
> >> > +#define FME_PR_DFH 0x0
> >> > +#define FME_PR_CTRL 0x8
> >> > +#define FME_PR_STS 0x10
> >> > +#define FME_PR_DATA 0x18
> >> > +#define FME_PR_ERR 0x20
> >> > +#define FME_PR_INTFC_ID_H 0xA8
> >> > +#define FME_PR_INTFC_ID_L 0xB0
> >> > +
> >> > +/* FME PR Control Register Bitfield */
> >> > +#define FME_PR_CTRL_PR_RST BIT(0) /* Reset PR engine */
> >> > +#define FME_PR_CTRL_PR_RSTACK BIT(4) /* Ack for PR engine reset */
> >> > +#define FME_PR_CTRL_PR_RGN_ID GENMASK_ULL(9, 7) /* PR Region ID */
> >> > +#define FME_PR_CTRL_PR_START BIT(12) /* Start to request for PR service */
> >> > +#define FME_PR_CTRL_PR_COMPLETE BIT(13) /* PR data push complete notification */
> >> > +
> >> > +/* FME PR Status Register Bitfield */
> >> > +/* Number of available entries in HW queue inside the PR engine. */
> >> > +#define FME_PR_STS_PR_CREDIT GENMASK_ULL(8, 0)
> >> > +#define FME_PR_STS_PR_STS BIT(16) /* PR operation status */
> >> > +#define FME_PR_STS_PR_STS_IDLE 0
> >> > +#define FME_PR_STS_PR_CTRLR_STS GENMASK_ULL(22, 20) /* Controller status */
> >> > +#define FME_PR_STS_PR_HOST_STS GENMASK_ULL(27, 24) /* PR host status */
> >> > +
> >> > +/* FME PR Data Register Bitfield */
> >> > +/* PR data from the raw-binary file. */
> >> > +#define FME_PR_DATA_PR_DATA_RAW GENMASK_ULL(32, 0)
> >> > +
> >> > +/* FME PR Error Register */
> >> > +/* PR Operation errors detected. */
> >> > +#define FME_PR_ERR_OPERATION_ERR BIT(0)
> >> > +/* CRC error detected. */
> >> > +#define FME_PR_ERR_CRC_ERR BIT(1)
> >> > +/* Incompatible PR bitstream detected. */
> >> > +#define FME_PR_ERR_INCOMPATIBLE_BS BIT(2)
> >> > +/* PR data push protocol violated. */
> >> > +#define FME_PR_ERR_PROTOCOL_ERR BIT(3)
> >> > +/* PR data fifo overflow error detected */
> >> > +#define FME_PR_ERR_FIFO_OVERFLOW BIT(4)
> >>
> >> This stuff is specific to this FPGA manager device, so it should
> >> either be in the dfl-fme-mgr.c or in a dfl-fme-mgr.h
> >
> > same as above, I can fix this in the next version.
> >
> > Thanks
> > Hao
>
> Thanks,
> Alan

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