linux-kernel - RE: [EXTERNAL] [PATCH] vdpa/octeon_ep: Use non-hybrid PCI devres API

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Message-ID:
 <MW4PR18MB5244915E54967510C5356B4DA6BC2@MW4PR18MB5244.namprd18.prod.outlook.com>
Date: Thu, 17 Apr 2025 09:02:08 +0000
From: Vamsi Krishna Attunuru <vattunuru@...vell.com>
To: Philipp Stanner <phasta@...nel.org>, Srujana Challa <schalla@...vell.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Xuan
 Zhuo <xuanzhuo@...ux.alibaba.com>,
        Eugenio Pérez
	<eperezma@...hat.com>,
        Shijith Thotton <sthotton@...vell.com>,
        Dan Carpenter
	<dan.carpenter@...aro.org>,
        Satha Koteswara Rao Kottidi
	<skoteshwar@...vell.com>
CC: "virtualization@...ts.linux.dev" <virtualization@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [EXTERNAL] [PATCH] vdpa/octeon_ep: Use non-hybrid PCI devres API



>-----Original Message-----
>From: Philipp Stanner <phasta@...nel.org>
>Sent: Thursday, April 17, 2025 1:32 PM
>To: Srujana Challa <schalla@...vell.com>; Vamsi Krishna Attunuru
><vattunuru@...vell.com>; Michael S. Tsirkin <mst@...hat.com>; Jason
>Wang <jasowang@...hat.com>; Xuan Zhuo <xuanzhuo@...ux.alibaba.com>;
>Eugenio Pérez <eperezma@...hat.com>; Shijith Thotton
><sthotton@...vell.com>; Dan Carpenter <dan.carpenter@...aro.org>;
>Philipp Stanner <phasta@...nel.org>; Satha Koteswara Rao Kottidi
><skoteshwar@...vell.com>
>Cc: virtualization@...ts.linux.dev; linux-kernel@...r.kernel.org
>Subject: [EXTERNAL] [PATCH] vdpa/octeon_ep: Use non-hybrid PCI devres
>API
>
>octeon enables its PCI device with pcim_enable_device(). This, implicitly,
>switches the function pci_request_region() into managed mode, where it
>becomes a devres function. The PCI subsystem wants to remove this hybrid
>nature from its interfaces. 
>octeon enables its PCI device with pcim_enable_device(). This, implicitly,
>switches the function pci_request_region() into managed mode, where it
>becomes a devres function.
>
>The PCI subsystem wants to remove this hybrid nature from its interfaces. To
>do so, users of the aforementioned combination of functions must be ported
>to non-hybrid functions.
>
>Moreover, since both functions are already managed in this driver, the calls to
>pci_release_region() are unnecessary.
>
>Remove the calls to pci_release_region().
>
>Replace the call to sometimes-managed pci_request_region() with one to the
>always-managed pcim_request_region().

Thanks you, Philipps, for the patch. The Octeon EP driver does not use managed calls for handling resource regions. 
This is because the PCIe PF function reduces its resources to share them with its VFs and later restores them to original size
once the VFs are released. Due to this resource sharing requirement, the driver cannot use the always-managed request
regions calls.

>
>Signed-off-by: Philipp Stanner <phasta@...nel.org>
>---
> drivers/vdpa/octeon_ep/octep_vdpa_main.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
>
>diff --git a/drivers/vdpa/octeon_ep/octep_vdpa_main.c
>b/drivers/vdpa/octeon_ep/octep_vdpa_main.c
>index f3d4dda4e04c..e0da6367661e 100644
>--- a/drivers/vdpa/octeon_ep/octep_vdpa_main.c
>+++ b/drivers/vdpa/octeon_ep/octep_vdpa_main.c
>@@ -391,7 +391,7 @@ static int octep_iomap_region(struct pci_dev *pdev,
>u8 __iomem **tbl, u8 bar)  {
> 	int ret;
>
>-	ret = pci_request_region(pdev, bar, OCTEP_VDPA_DRIVER_NAME);
>+	ret = pcim_request_region(pdev, bar, OCTEP_VDPA_DRIVER_NAME);
> 	if (ret) {
> 		dev_err(&pdev->dev, "Failed to request BAR:%u region\n",
>bar);
> 		return ret;
>@@ -400,7 +400,6 @@ static int octep_iomap_region(struct pci_dev *pdev,
>u8 __iomem **tbl, u8 bar)
> 	tbl[bar] = pci_iomap(pdev, bar, pci_resource_len(pdev, bar));
> 	if (!tbl[bar]) {
> 		dev_err(&pdev->dev, "Failed to iomap BAR:%u\n", bar);
>-		pci_release_region(pdev, bar);
> 		ret = -ENOMEM;
> 	}
>
>@@ -410,7 +409,6 @@ static int octep_iomap_region(struct pci_dev *pdev,
>u8 __iomem **tbl, u8 bar)  static void octep_iounmap_region(struct pci_dev
>*pdev, u8 __iomem **tbl, u8 bar)  {
> 	pci_iounmap(pdev, tbl[bar]);
>-	pci_release_region(pdev, bar);
> }
>
> static void octep_vdpa_pf_bar_shrink(struct octep_pf *octpf)
>--
>2.48.1