Re: [PATCH 06/24] RISC-V: ACPI: Add PCI functions to build ACPI core

[Conor Dooley]

On Mon, Jan 30, 2023 at 11:52:07PM +0530, Sunil V L wrote:
> When CONFIG_PCI is enabled, ACPI core expects few arch
> functions related to PCI. Add those functions so that
> ACPI core gets build. These are levraged from arm64.
> 
> Signed-off-by: Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>
> ---
>  arch/riscv/kernel/Makefile |   1 +
>  arch/riscv/kernel/pci.c    | 173 +++++++++++++++++++++++++++++++++++++
>  2 files changed, 174 insertions(+)
>  create mode 100644 arch/riscv/kernel/pci.c

> diff --git a/arch/riscv/kernel/pci.c b/arch/riscv/kernel/pci.c
> new file mode 100644
> index 000000000000..3388af3a67a0
> --- /dev/null
> +++ b/arch/riscv/kernel/pci.c
> @@ -0,0 +1,173 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Code borrowed from ARM64
> + *
> + * Copyright (C) 2003 Anton Blanchard <anton@xxxxxxxxxx>, IBM
> + * Copyright (C) 2014 ARM Ltd.
> + * Copyright (C) 2022-2023 Ventana Micro System Inc.
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/init.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/mm.h>
> +#include <linux/pci.h>
> +#include <linux/pci-acpi.h>
> +#include <linux/pci-ecam.h>
> +
> +#ifdef CONFIG_ACPI

Quickly checking against ARM64, they do not wrap the read/write
functions in this ifdef, so why do we need to do so?

> +/*
> + * raw_pci_read/write - Platform-specific PCI config space access.
> + */
> +int raw_pci_read(unsigned int domain, unsigned int bus,
> +		  unsigned int devfn, int reg, int len, u32 *val)
> +{
> +	struct pci_bus *b = pci_find_bus(domain, bus);
> +
> +	if (!b)
> +		return PCIBIOS_DEVICE_NOT_FOUND;
> +	return b->ops->read(b, devfn, reg, len, val);

A newline before the return would be appreciated by my eyes :)

> +}
> +
> +int raw_pci_write(unsigned int domain, unsigned int bus,
> +		unsigned int devfn, int reg, int len, u32 val)

Also, both read and write functions here appear to have incorrect
alignment on the second lines.

> +{
> +	struct pci_bus *b = pci_find_bus(domain, bus);
> +
> +	if (!b)
> +		return PCIBIOS_DEVICE_NOT_FOUND;
> +	return b->ops->write(b, devfn, reg, len, val);
> +}
> +
> +

Extra newline here too, looks to be exactly where you deleted the numa
stuff from arm64 ;)

> +struct acpi_pci_generic_root_info {
> +	struct acpi_pci_root_info	common;
> +	struct pci_config_window	*cfg;	/* config space mapping */
> +};
> +
> +int acpi_pci_bus_find_domain_nr(struct pci_bus *bus)
> +{
> +	struct pci_config_window *cfg = bus->sysdata;
> +	struct acpi_device *adev = to_acpi_device(cfg->parent);
> +	struct acpi_pci_root *root = acpi_driver_data(adev);
> +
> +	return root->segment;
> +}
> +
> +static int pci_acpi_root_prepare_resources(struct acpi_pci_root_info *ci)

Rhetorical question perhaps, but what does "ci" mean?

> +{
> +	struct resource_entry *entry, *tmp;
> +	int status;
> +
> +	status = acpi_pci_probe_root_resources(ci);
> +	resource_list_for_each_entry_safe(entry, tmp, &ci->resources) {
> +		if (!(entry->res->flags & IORESOURCE_WINDOW))
> +			resource_list_destroy_entry(entry);
> +	}
> +	return status;

Perhaps that extra newline from above could migrate down to the line
above the return here.

> +}
> +
> +/*
> + * Lookup the bus range for the domain in MCFG, and set up config space
> + * mapping.
> + */
> +static struct pci_config_window *
> +pci_acpi_setup_ecam_mapping(struct acpi_pci_root *root)

This all fits on 1 line.

> +{
> +	struct device *dev = &root->device->dev;
> +	struct resource *bus_res = &root->secondary;
> +	u16 seg = root->segment;
> +	const struct pci_ecam_ops *ecam_ops;
> +	struct resource cfgres;
> +	struct acpi_device *adev;
> +	struct pci_config_window *cfg;
> +	int ret;
> +
> +	ret = pci_mcfg_lookup(root, &cfgres, &ecam_ops);
> +	if (ret) {
> +		dev_err(dev, "%04x:%pR ECAM region not found\n", seg, bus_res);
> +		return NULL;
> +	}
> +
> +	adev = acpi_resource_consumer(&cfgres);
> +	if (adev)
> +		dev_info(dev, "ECAM area %pR reserved by %s\n", &cfgres,
> +			 dev_name(&adev->dev));
> +	else
> +		dev_warn(dev, FW_BUG "ECAM area %pR not reserved in ACPI namespace\n",
> +			 &cfgres);
> +
> +	cfg = pci_ecam_create(dev, &cfgres, bus_res, ecam_ops);
> +	if (IS_ERR(cfg)) {
> +		dev_err(dev, "%04x:%pR error %ld mapping ECAM\n", seg, bus_res,
> +			PTR_ERR(cfg));
> +		return NULL;
> +	}
> +
> +	return cfg;
> +}
> +
> +/* release_info: free resources allocated by init_info */

The fact that you haven't picked a consistent comment style for this
functions really bothers my OCD. Yes, it may be copy-paste from arm64,
but since this is "new code" I don't think there's harm in at least
*starting* with something that looks cohesive.

> +static void pci_acpi_generic_release_info(struct acpi_pci_root_info *ci)
> +{
> +	struct acpi_pci_generic_root_info *ri;
> +
> +	ri = container_of(ci, struct acpi_pci_generic_root_info, common);
> +	pci_ecam_free(ri->cfg);
> +	kfree(ci->ops);
> +	kfree(ri);
> +}
> +
> +

Extra newline here.

> +/* Interface called from ACPI code to setup PCI host controller */
> +struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
> +{
> +	struct acpi_pci_generic_root_info *ri;
> +	struct pci_bus *bus, *child;
> +	struct acpi_pci_root_ops *root_ops;
> +	struct pci_host_bridge *host;
> +
> +	ri = kzalloc(sizeof(*ri), GFP_KERNEL);
> +	if (!ri)
> +		return NULL;
> +
> +	root_ops = kzalloc(sizeof(*root_ops), GFP_KERNEL);
> +	if (!root_ops) {
> +		kfree(ri);
> +		return NULL;
> +	}
> +
> +	ri->cfg = pci_acpi_setup_ecam_mapping(root);
> +	if (!ri->cfg) {
> +		kfree(ri);
> +		kfree(root_ops);
> +		return NULL;
> +	}
> +
> +	root_ops->release_info = pci_acpi_generic_release_info;
> +	root_ops->prepare_resources = pci_acpi_root_prepare_resources;
> +	root_ops->pci_ops = (struct pci_ops *)&ri->cfg->ops->pci_ops;
> +	bus = acpi_pci_root_create(root, root_ops, &ri->common, ri->cfg);
> +	if (!bus)
> +		return NULL;
> +
> +	/* If we must preserve the resource configuration, claim now */
> +	host = pci_find_host_bridge(bus);
> +	if (host->preserve_config)
> +		pci_bus_claim_resources(bus);
> +
> +	/*
> +	 * Assign whatever was left unassigned. If we didn't claim above,
> +	 * this will reassign everything.
> +	 */
> +	pci_assign_unassigned_root_bus_resources(bus);
> +
> +	list_for_each_entry(child, &bus->children, node)
> +		pcie_bus_configure_settings(child);
> +
> +	return bus;
> +}

Anyways, this does look to be "leveraged from arm64" as you say and I
only had minor nits to comment about...
Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>

Cheers,
Conor.

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