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From:   "Wu, Hao" <hao.wu@intel.com>
To:     "Zhang, Tianfei" <tianfei.zhang@intel.com>,
        "trix@redhat.com" <trix@redhat.com>,
        "mdf@kernel.org" <mdf@kernel.org>,
        "Xu, Yilun" <yilun.xu@intel.com>,
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CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "corbet@lwn.net" <corbet@lwn.net>,
        Matthew Gerlach <matthew.gerlach@linux.intel.com>
Subject: RE: [PATCH v3 1/5] fpga: dfl: Allow for ports without specific bar
 space.
Thread-Topic: [PATCH v3 1/5] fpga: dfl: Allow for ports without specific bar
 space.
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Date:   Tue, 1 Mar 2022 06:44:24 +0000
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References: <20220301062123.818687-1-tianfei.zhang@intel.com>
 <20220301062123.818687-2-tianfei.zhang@intel.com>
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> -----Original Message-----
> From: Zhang, Tianfei <tianfei.zhang@intel.com>
> Sent: Tuesday, March 1, 2022 2:21 PM
> To: Wu, Hao <hao.wu@intel.com>; trix@redhat.com; mdf@kernel.org; Xu, Yilu=
n
> <yilun.xu@intel.com>; linux-fpga@vger.kernel.org; linux-doc@vger.kernel.o=
rg
> Cc: linux-kernel@vger.kernel.org; corbet@lwn.net; Matthew Gerlach
> <matthew.gerlach@linux.intel.com>; Zhang, Tianfei <tianfei.zhang@intel.co=
m>
> Subject: [PATCH v3 1/5] fpga: dfl: Allow for ports without specific bar s=
pace.
>=20
> From: Matthew Gerlach <matthew.gerlach@linux.intel.com>
>=20
> In OFS, there is a Port device for each PR slot, like Port
> control, Port user clock control and Port errors, those feature
> devices are linked with DFL. The DFL of Port device was located
> in PCIe Bar 0 MMIO space by default, but it also can put into any

There is not default BAR for Port. In OFS implementation it could
be 0, but not default value for other implementation.

> PCIe Bar space. If the BarID (3bits field) in PORTn_OFFSET register
> set to invalid means that DFL of Port device is located in the Bar 0
> by default, in this case, it don't need add the Bar 0 into dfl list
> twice.

So why not just use existing method (e.g. BAR0 + offset) to locate
DFL of port?

The title is confusing too, PORTs still have its BAR location/space.

Hao

>=20
> ---
> v2: use FME_HDR_NO_PORT_BAR instead of PCI_STD_NUM_BARS.
>=20
> Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
> Signed-off-by: Tianfei Zhang <tianfei.zhang@intel.com>
> ---
>  drivers/fpga/dfl-pci.c | 6 ++++++
>  drivers/fpga/dfl.h     | 1 +
>  2 files changed, 7 insertions(+)
>=20
> diff --git a/drivers/fpga/dfl-pci.c b/drivers/fpga/dfl-pci.c
> index 4d68719e608f..33545c999c06 100644
> --- a/drivers/fpga/dfl-pci.c
> +++ b/drivers/fpga/dfl-pci.c
> @@ -258,6 +258,12 @@ static int find_dfls_by_default(struct pci_dev *pcid=
ev,
>  			 */
>  			bar =3D FIELD_GET(FME_PORT_OFST_BAR_ID, v);
>  			offset =3D FIELD_GET(FME_PORT_OFST_DFH_OFST, v);
> +			if (bar >=3D FME_HDR_NO_PORT_BAR) {
> +				dev_dbg(&pcidev->dev, "skipping port without
> specific BAR space %d\n",
> +					bar);
> +				continue;
> +			}
> +
>  			start =3D pci_resource_start(pcidev, bar) + offset;
>  			len =3D pci_resource_len(pcidev, bar) - offset;
>=20
> diff --git a/drivers/fpga/dfl.h b/drivers/fpga/dfl.h
> index 53572c7aced0..1fd493e82dd8 100644
> --- a/drivers/fpga/dfl.h
> +++ b/drivers/fpga/dfl.h
> @@ -91,6 +91,7 @@
>  #define FME_HDR_PORT_OFST(n)	(0x38 + ((n) * 0x8))
>  #define FME_HDR_BITSTREAM_ID	0x60
>  #define FME_HDR_BITSTREAM_MD	0x68
> +#define FME_HDR_NO_PORT_BAR	7
>=20
>  /* FME Fab Capability Register Bitfield */
>  #define FME_CAP_FABRIC_VERID	GENMASK_ULL(7, 0)	/* Fabric
> version ID */
> --
> 2.26.2