linux-kernel - Re: [External] : [PATCH v2 1/2] dmaengine: dw-edma: Add AMD MDB Endpoint Support

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Message-ID: <20250916150532.GA1797586@bhelgaas>
Date: Tue, 16 Sep 2025 10:05:32 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: ALOK TIWARI <alok.a.tiwari@...cle.com>
Cc: Devendra K Verma <devendra.verma@....com>, bhelgaas@...gle.com,
	mani@...nel.org, vkoul@...nel.org, dmaengine@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	michal.simek@....com
Subject: Re: [External] : [PATCH v2 1/2] dmaengine: dw-edma: Add AMD MDB
 Endpoint Support

On Tue, Sep 16, 2025 at 04:25:49PM +0530, ALOK TIWARI wrote:
> 
> 
> On 9/16/2025 4:13 PM, Devendra K Verma wrote:
> > +	/*
> > +	 * Synopsys and AMD (Xilinx) use the same VSEC ID for the purpose
> > +	 * of map, channel counts, etc.
> > +	 */
> > +	if (vendor != PCI_VENDOR_ID_SYNOPSYS ||
> > +	    vendor != PCI_VENDOR_ID_XILINX)
> > +		return;
> 
> if, vendor == PCI_VENDOR_ID_XILINX condition will true
> 
> should not be if (vendor != PCI_VENDOR_ID_SYNOPSYS && vendor !=
> PCI_VENDOR_ID_XILINX) ?

Good catch, I mistakenly said this part was correct, but you're right;
it's obviously broken.

The alternate structure I suggested would avoid this problem.

> > +
> > +	cap = DW_PCIE_VSEC_DMA_ID;
> > +	if (vendor == PCI_VENDOR_ID_XILINX)
> > +		cap = DW_PCIE_XILINX_MDB_VSEC_ID;
> > +
> > +	vsec = pci_find_vsec_capability(pdev, vendor, cap);
> >   	if (!vsec)
> 
> 
> Thanks,
> Alok