linux-kernel - Re: [PATCH v1 3/7] fpga: dfl: Allow for ports with no local bar space.

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Date:   Tue, 15 Feb 2022 07:05:55 -0800
From:   Tom Rix <trix@...hat.com>
To:     Tianfei zhang <tianfei.zhang@...el.com>, hao.wu@...el.com,
        mdf@...nel.org, yilun.xu@...el.com, linux-fpga@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     corbet@....net, Matthew Gerlach <matthew.gerlach@...ux.intel.com>
Subject: Re: [PATCH v1 3/7] fpga: dfl: Allow for ports with no local bar
 space.


On 2/14/22 3:26 AM, Tianfei zhang wrote:
> From: Matthew Gerlach <matthew.gerlach@...ux.intel.com>
>
>  From a fpga partial reconfiguration standpoint, a port
> may not be connected any local BAR space.  The port could
> be connected to a different PCIe Physical Function (PF) or
> Virtual Function (VF), in which case another driver instance
> would manage the endpoint.

It is not clear if this is part of iofs or a bug fix.

> Signed-off-by: Matthew Gerlach <matthew.gerlach@...ux.intel.com>
> Signed-off-by: Tianfei Zhang <tianfei.zhang@...el.com>
> ---
>   drivers/fpga/dfl-pci.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
>
> diff --git a/drivers/fpga/dfl-pci.c b/drivers/fpga/dfl-pci.c
> index 4d68719e608f..8abd9b408403 100644
> --- a/drivers/fpga/dfl-pci.c
> +++ b/drivers/fpga/dfl-pci.c
> @@ -243,6 +243,7 @@ static int find_dfls_by_default(struct pci_dev *pcidev,
>   		v = readq(base + FME_HDR_CAP);
>   		port_num = FIELD_GET(FME_CAP_NUM_PORTS, v);
>   
> +		dev_info(&pcidev->dev, "port_num = %d\n", port_num);
>   		WARN_ON(port_num > MAX_DFL_FPGA_PORT_NUM);
>   
>   		for (i = 0; i < port_num; i++) {
> @@ -258,6 +259,13 @@ static int find_dfls_by_default(struct pci_dev *pcidev,
>   			 */
>   			bar = FIELD_GET(FME_PORT_OFST_BAR_ID, v);
>   			offset = FIELD_GET(FME_PORT_OFST_DFH_OFST, v);
> +			if (bar >= PCI_STD_NUM_BARS) {

Is bar set to a better magic number that pci_std_num_bars ? maybe 0xff's

How do you tell between this case and broken hw ?

Move up a line and skip getting an offset that will not be used.

> +				dev_info(&pcidev->dev, "skipping port without local BAR space %d\n",
> +					 bar);
> +				continue;
> +			} else {
> +				dev_info(&pcidev->dev, "BAR %d offset %u\n", bar, offset);
> +			}
>   			start = pci_resource_start(pcidev, bar) + offset;
>   			len = pci_resource_len(pcidev, bar) - offset;
>   

Is similar logic needed for else-if (port) block below this ?

Tom