linux-kernel - RE: [PATCH v3 4/5] fpga: dfl: Handle dfl's starting with AFU

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Date:   Wed, 2 Mar 2022 02:42:57 +0000
From:   "Zhang, Tianfei" <tianfei.zhang@...el.com>
To:     "Wu, Hao" <hao.wu@...el.com>, "trix@...hat.com" <trix@...hat.com>,
        "mdf@...nel.org" <mdf@...nel.org>,
        "Xu, Yilun" <yilun.xu@...el.com>,
        "linux-fpga@...r.kernel.org" <linux-fpga@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "corbet@....net" <corbet@....net>,
        Matthew Gerlach <matthew.gerlach@...ux.intel.com>
Subject: RE: [PATCH v3 4/5] fpga: dfl: Handle dfl's starting with AFU



> -----Original Message-----
> From: Wu, Hao <hao.wu@...el.com>
> Sent: Tuesday, March 1, 2022 3:28 PM
> To: Zhang, Tianfei <tianfei.zhang@...el.com>; trix@...hat.com;
> mdf@...nel.org; Xu, Yilun <yilun.xu@...el.com>; linux-fpga@...r.kernel.org;
> linux-doc@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org; corbet@....net; Matthew Gerlach
> <matthew.gerlach@...ux.intel.com>
> Subject: RE: [PATCH v3 4/5] fpga: dfl: Handle dfl's starting with AFU
> 
> > -----Original Message-----
> > From: Zhang, Tianfei <tianfei.zhang@...el.com>
> > Sent: Tuesday, March 1, 2022 2:21 PM
> > To: Wu, Hao <hao.wu@...el.com>; trix@...hat.com; mdf@...nel.org; Xu,
> > Yilun <yilun.xu@...el.com>; linux-fpga@...r.kernel.org;
> > linux-doc@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org; corbet@....net; Matthew Gerlach
> > <matthew.gerlach@...ux.intel.com>; Zhang, Tianfei
> > <tianfei.zhang@...el.com>
> > Subject: [PATCH v3 4/5] fpga: dfl: Handle dfl's starting with AFU
> >
> > From: Matthew Gerlach <matthew.gerlach@...ux.intel.com>
> >
> > Allow for a Device Feature List (DFL) to start with a Device Feature
> > Header (DFH) of type Accelerator Function Unit (AFU) by doing nothing.
> > This allows for PCIe VFs to be created.
> 
> Why this is related to VFs creation? We don't have AFU in PF in OFS case, right?

Yes, in " Multiple VFs per PR slot" model, the AFU was not connected with Port.

> 
> >
> > Signed-off-by: Matthew Gerlach <matthew.gerlach@...ux.intel.com>
> > Signed-off-by: Tianfei Zhang <tianfei.zhang@...el.com>
> > ---
> >  drivers/fpga/dfl-pci.c |  7 ++++++-
> >  drivers/fpga/dfl.c     | 22 +++++++++++++---------
> >  2 files changed, 19 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/fpga/dfl-pci.c b/drivers/fpga/dfl-pci.c index
> > 33545c999c06..e7d58e7b1bbd 100644
> > --- a/drivers/fpga/dfl-pci.c
> > +++ b/drivers/fpga/dfl-pci.c
> > @@ -275,7 +275,12 @@ static int find_dfls_by_default(struct pci_dev
> > *pcidev,
> >
> >  		dfl_fpga_enum_info_add_dfl(info, start, len);
> >  	} else {
> 
> Can be something like else if dfl_feature_is_afu(base) following the same style.

dfl_feature_is_afu(base) will be better.

> 
> > -		ret = -ENODEV;
> > +		v = readq(base + DFH);
> > +		if (FIELD_GET(DFH_TYPE, v) != DFH_TYPE_AFU) {
> > +			dev_info(&pcidev->dev, "Unknown feature type 0x%llx
> > id 0x%llx\n",
> > +				 FIELD_GET(DFH_TYPE, v), FIELD_GET(DFH_ID,
> > v));
> > +			ret = -ENODEV;
> > +		}
> 
> But nothing else done for AFU so far? How it works? Sounds like more patches
> are required.

In " Multiple VFs per PR slot" model, we access the AFU resource via VFs for example VFIO-PIC driver, and we cannot access the AFU MMIO resource by AFU APIs.

> 
> >  	}
> >
> >  	/* release I/O mappings for next step enumeration */ diff --git
> > a/drivers/fpga/dfl.c b/drivers/fpga/dfl.c index
> > fd04ef5c8b03..e30bbb3039cd 100644
> > --- a/drivers/fpga/dfl.c
> > +++ b/drivers/fpga/dfl.c
> > @@ -900,9 +900,11 @@ static void build_info_free(struct
> > build_feature_devs_info *binfo)
> >  		dfl_id_free(feature_dev_id_type(binfo->feature_dev),
> >  			    binfo->feature_dev->id);
> >
> > -		list_for_each_entry_safe(finfo, p, &binfo->sub_features, node)
> > {
> > -			list_del(&finfo->node);
> > -			kfree(finfo);
> > +		if (!list_empty(&binfo->sub_features)) {
> > +			list_for_each_entry_safe(finfo, p, &binfo-
> > >sub_features, node) {
> > +				list_del(&finfo->node);
> > +				kfree(finfo);
> > +			}
> >  		}
> >  	}
> >
> > @@ -1439,12 +1441,14 @@ dfl_fpga_feature_devs_enumerate(struct
> > dfl_fpga_enum_info *info)
> >  	 * start enumeration for all feature devices based on Device Feature
> >  	 * Lists.
> >  	 */
> > -	list_for_each_entry(dfl, &info->dfls, node) {
> > -		ret = parse_feature_list(binfo, dfl->start, dfl->len);
> > -		if (ret) {
> > -			remove_feature_devs(cdev);
> > -			build_info_free(binfo);
> > -			goto unregister_region_exit;
> > +	if (!list_empty(&info->dfls)) {
> > +		list_for_each_entry(dfl, &info->dfls, node) {
> > +			ret = parse_feature_list(binfo, dfl->start, dfl->len);
> > +			if (ret) {
> > +				remove_feature_devs(cdev);
> > +				build_info_free(binfo);
> > +				goto unregister_region_exit;
> > +			}
> >  		}
> >  	}
> >
> > --
> > 2.26.2