linux-kernel - [PATCH v2 1/2] PCI: Add enable_device() and disable

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Message-Id: <20240930-imx95_lut-v2-1-3b6467ba539a@nxp.com>
Date: Mon, 30 Sep 2024 15:42:21 -0400
From: Frank Li <Frank.Li@....com>
To: Bjorn Helgaas <bhelgaas@...gle.com>, Richard Zhu <hongxing.zhu@....com>, 
 Lucas Stach <l.stach@...gutronix.de>, 
 Lorenzo Pieralisi <lpieralisi@...nel.org>, 
 Krzysztof Wilczyński <kw@...ux.com>, 
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, 
 Rob Herring <robh@...nel.org>, Shawn Guo <shawnguo@...nel.org>, 
 Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-arm-kernel@...ts.infradead.org, imx@...ts.linux.dev, Frank.li@....com, 
 alyssa@...enzweig.io, bpf@...r.kernel.org, broonie@...nel.org, jgg@...pe.ca, 
 joro@...tes.org, l.stach@...gutronix.de, lgirdwood@...il.com, 
 maz@...nel.org, p.zabel@...gutronix.de, robin.murphy@....com, 
 will@...nel.org, Frank Li <Frank.Li@....com>
Subject: [PATCH v2 1/2] PCI: Add enable_device() and disable_device()
 callbacks for bridges

Some PCIe bridges require special handling when enabling or disabling
PCIe devices. For example, on the i.MX95 platform, a lookup table must be
configured to inform the hardware how to convert pci_device_id to stream
(bus master) ID, which is used by the IOMMU and MSI controller to identify
bus master device.

Enablement will be failure when there is not enough lookup table resource.
Avoid DMA write to wrong position. That is the reason why pci_fixup_enable
can't work since not return value for fixup function.

Signed-off-by: Frank Li <Frank.Li@....com>
---
Change from v1 to v2
- move enable(disable)device ops to pci_host_bridge
---
 drivers/pci/pci.c   | 14 ++++++++++++++
 include/linux/pci.h |  2 ++
 2 files changed, 16 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 7d85c04fbba2a..fcdeb12622568 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2056,6 +2056,7 @@ int __weak pcibios_enable_device(struct pci_dev *dev, int bars)
 static int do_pci_enable_device(struct pci_dev *dev, int bars)
 {
 	int err;
+	struct pci_host_bridge *host_bridge;
 	struct pci_dev *bridge;
 	u16 cmd;
 	u8 pin;
@@ -2068,6 +2069,13 @@ static int do_pci_enable_device(struct pci_dev *dev, int bars)
 	if (bridge)
 		pcie_aspm_powersave_config_link(bridge);
 
+	host_bridge = pci_find_host_bridge(dev->bus);
+	if (host_bridge && host_bridge->enable_device) {
+		err = host_bridge->enable_device(host_bridge, dev);
+		if (err)
+			return err;
+	}
+
 	err = pcibios_enable_device(dev, bars);
 	if (err < 0)
 		return err;
@@ -2262,12 +2270,18 @@ void pci_disable_enabled_device(struct pci_dev *dev)
  */
 void pci_disable_device(struct pci_dev *dev)
 {
+	struct pci_host_bridge *host_bridge;
+
 	dev_WARN_ONCE(&dev->dev, atomic_read(&dev->enable_cnt) <= 0,
 		      "disabling already-disabled device");
 
 	if (atomic_dec_return(&dev->enable_cnt) != 0)
 		return;
 
+	host_bridge = pci_find_host_bridge(dev->bus);
+	if (host_bridge && host_bridge->disable_device)
+		host_bridge->disable_device(host_bridge, dev);
+
 	do_pci_disable_device(dev);
 
 	dev->is_busmaster = 0;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 573b4c4c2be61..ac15b02e14ddd 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -578,6 +578,8 @@ struct pci_host_bridge {
 	u8 (*swizzle_irq)(struct pci_dev *, u8 *); /* Platform IRQ swizzler */
 	int (*map_irq)(const struct pci_dev *, u8, u8);
 	void (*release_fn)(struct pci_host_bridge *);
+	int (*enable_device)(struct pci_host_bridge *bridge, struct pci_dev *dev);
+	void (*disable_device)(struct pci_host_bridge *bridge, struct pci_dev *dev);
 	void		*release_data;
 	unsigned int	ignore_reset_delay:1;	/* For entire hierarchy */
 	unsigned int	no_ext_tags:1;		/* No Extended Tags */

-- 
2.34.1