Subject: [PATCH v4 2/2] pci, pci-thunder-pem: Add PCIe host driver for ThunderX processors.

From: [email-masked] (Bjorn Helgaas)
Date: Thu, 4 Feb 2016 18:04:52 -0600

Hi David,

Looks good, a few trival questions below.

On Tue, Jan 26, 2016 at 01:46:21PM -0800, David Daney wrote:
> From: David Daney <[email-masked]>
> 
> Some Cavium ThunderX processors require quirky access methods for the
> config space of the PCIe bridge.  Add a driver to provide these config
> space accessor functions.  The pci-host-common code is used to
> configure the PCI machinery.
> 
> Signed-off-by: David Daney <[email-masked]>
> Acked-by: Rob Herring <[email-masked]>
> Acked-by: Arnd Bergmann <[email-masked]>
> ---
>  .../devicetree/bindings/pci/pci-thunder-pem.txt    |  43 ++++
>  MAINTAINERS                                        |   8 +
>  drivers/pci/host/Kconfig                           |   7 +
>  drivers/pci/host/Makefile                          |   1 +
>  drivers/pci/host/pci-thunder-pem.c                 | 283 +++++++++++++++++++++

What's the significance of the "pem" part of the name?  I'm wondering
if we can shorten the filenames and function names by dropping it and
referring to this simply as "thunder" or "thunderx".

>  5 files changed, 342 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/pci/pci-thunder-pem.txt
>  create mode 100644 drivers/pci/host/pci-thunder-pem.c
> 
> diff --git a/Documentation/devicetree/bindings/pci/pci-thunder-pem.txt b/Documentation/devicetree/bindings/pci/pci-thunder-pem.txt
> new file mode 100644
> index 0000000..f131fae
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pci/pci-thunder-pem.txt
> @@ -0,0 +1,43 @@
> +* ThunderX PEM PCIe host controller
> +
> +Firmware-initialized PCI host controller found on some Cavium
> +ThunderX processors.
> +
> +The properties and their meanings are identical to those described in
> +host-generic-pci.txt except as listed below.
> +
> +Properties of the host controller node that differ from
> +host-generic-pci.txt:
> +
> +- compatible     : Must be "cavium,pci-host-thunder-pem"
> +
> +- reg            : Two entries: First the configuration space for down
> +                   stream devices base address and size, as accessed
> +                   from the parent bus. Second, the register bank of
> +                   the PEM device PCIe bridge.
> +
> +Example:
> +
> +    pci at 87e0,c2000000 {
> +	compatible = "cavium,pci-host-thunder-pem";
> +	device_type = "pci";
> +	msi-parent = <&its>;
> +	msi-map = <0 &its 0x10000 0x10000>;
> +	bus-range = <0x8f 0xc7>;
> +	#size-cells = <2>;
> +	#address-cells = <3>;
> +
> +	reg = <0x8880 0x8f000000 0x0 0x39000000>,  /* Configuration space */
> +	      <0x87e0 0xc2000000 0x0 0x00010000>; /* PEM space */
> +	ranges = <0x01000000 0x00 0x00020000 0x88b0 0x00020000 0x00 0x00010000>, /* I/O */
> +		 <0x03000000 0x00 0x10000000 0x8890 0x10000000 0x0f 0xf0000000>, /* mem64 */
> +		 <0x43000000 0x10 0x00000000 0x88a0 0x00000000 0x10 0x00000000>, /* mem64-pref */
> +		 <0x03000000 0x87e0 0xc2f00000 0x87e0 0xc2000000 0x00 0x00100000>; /* mem64 PEM BAR4 */
> +
> +	#interrupt-cells = <1>;
> +	interrupt-map-mask = <0 0 0 7>;
> +	interrupt-map = <0 0 0 1 &gic0 0 0 0 24 4>, /* INTA */
> +			<0 0 0 2 &gic0 0 0 0 25 4>, /* INTB */
> +			<0 0 0 3 &gic0 0 0 0 26 4>, /* INTC */
> +			<0 0 0 4 &gic0 0 0 0 27 4>; /* INTD */
> +    };
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 73c5bde..1aa8f82 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -8419,6 +8419,14 @@ L:     linux-arm-msm at vger.kernel.org
>  S:     Maintained
>  F:     drivers/pci/host/*qcom*
>  
> +PCIE DRIVER FOR CAVIUM THUNDERX
> +M:	David Daney <[email-masked]>
> +L:	linux-pci at vger.kernel.org
> +L:	linux-arm-kernel at lists.infradead.org (moderated for non-subscribers)
> +S:	Supported
> +F:	Documentation/devicetree/bindings/pci/pci-thunder-*
> +F:	drivers/pci/host/pci-thunder-*
> +
>  PCMCIA SUBSYSTEM
>  P:	Linux PCMCIA Team
>  L:	linux-pcmcia at lists.infradead.org
> diff --git a/drivers/pci/host/Kconfig b/drivers/pci/host/Kconfig
> index 65709b4..184df22 100644
> --- a/drivers/pci/host/Kconfig
> +++ b/drivers/pci/host/Kconfig
> @@ -195,4 +195,11 @@ config PCIE_QCOM
>  	  PCIe controller uses the Designware core plus Qualcomm-specific
>  	  hardware wrappers.
>  
> +config PCI_HOST_THUNDER_PEM
> +	bool "Cavium Thunder PCIe controller to off-chip devices"
> +	depends on OF && ARM64
> +	select PCI_HOST_COMMON
> +	help
> +	  Say Y here if you want PCIe support for CN88XX Cavium Thunder SoCs.
> +
>  endmenu
> diff --git a/drivers/pci/host/Makefile b/drivers/pci/host/Makefile
> index 3b24af8..8903172 100644
> --- a/drivers/pci/host/Makefile
> +++ b/drivers/pci/host/Makefile
> @@ -23,3 +23,4 @@ obj-$(CONFIG_PCIE_ALTERA) += pcie-altera.o
>  obj-$(CONFIG_PCIE_ALTERA_MSI) += pcie-altera-msi.o
>  obj-$(CONFIG_PCI_HISI) += pcie-hisi.o
>  obj-$(CONFIG_PCIE_QCOM) += pcie-qcom.o
> +obj-$(CONFIG_PCI_HOST_THUNDER_PEM) += pci-thunder-pem.o
> diff --git a/drivers/pci/host/pci-thunder-pem.c b/drivers/pci/host/pci-thunder-pem.c
> new file mode 100644
> index 0000000..43fa6f5
> --- /dev/null
> +++ b/drivers/pci/host/pci-thunder-pem.c
> @@ -0,0 +1,283 @@
> +/*
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> + *
> + * Copyright (C) 2015 Cavium, Inc.
> + *
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of_address.h>
> +#include <linux/of_pci.h>
> +#include <linux/platform_device.h>
> +
> +#include "pci-host-common.h"
> +
> +#define PEM_CFG_WR 0x28
> +#define PEM_CFG_RD 0x30
> +
> +struct thunder_pem_pci {
> +	struct gen_pci	gen_pci;
> +	u32		ea_entry[3];
> +	void __iomem	*pem_reg_base;
> +};
> +
> +static int thunder_pem_config_read(struct pci_bus *bus, unsigned int devfn,
> +				   int where, int size, u32 *val)
> +{
> +	int r;
> +	struct thunder_pem_pci *pem_pci;
> +	struct gen_pci *pci = bus->sysdata;
> +
> +	pem_pci = container_of(pci, struct thunder_pem_pci, gen_pci);
> +
> +	/*
> +	 * The first device on the bus in the PEM PCIe bridge.
> +	 * Special case its config access.
> +	 */
> +	if (bus->number == pci->cfg.bus_range->start) {
> +		u64 read_val;
> +
> +		if (devfn != 0 || where >= 2048) {
> +			*val = ~0;
> +			return PCIBIOS_DEVICE_NOT_FOUND;
> +		}
> +
> +		/*
> +		 * 32-bit accesses only.  Write the address to the low
> +		 * order bits of PEM_CFG_RD, then trigger the read by
> +		 * reading back.  The config data lands in the upper
> +		 * 32-bits of PEM_CFG_RD.
> +		 */
> +		read_val = where & ~3ull;
> +		writeq(read_val, pem_pci->pem_reg_base + PEM_CFG_RD);
> +		read_val = readq(pem_pci->pem_reg_base + PEM_CFG_RD);
> +		read_val >>= 32;
> +
> +		/*
> +		 * The config space contains some garbage, fix it up.
> +		 * Also synthesize an EA capability for the BAR used
> +		 * by MSI-X.
> +		 */
> +		switch (where & ~3u) {
> +		case 0x40:
> +			read_val &= 0xffff00ff;
> +			read_val |= 0x00007000; /* Skip MSI CAP */
> +			break;
> +		case 0x70: /* Express Cap */
> +			/* PME interrupt on vector 2*/
> +			read_val |= (2u << 25);
> +			break;
> +		case 0xb0: /* MSI-X Cap */
> +			/* TableSize=4, Next Cap is EA */
> +			read_val &= 0xc00000ff;
> +			read_val |= 0x0003bc00;
> +			break;
> +		case 0xb4:
> +			/* Table offset=0, BIR=0 */
> +			read_val = 0x00000000;
> +			break;
> +		case 0xb8:
> +			/* BPA offset=0xf0000, BIR=0 */
> +			read_val = 0x000f0000;
> +			break;
> +		case 0xbc:
> +			/* EA, 1 entry, no next Cap */
> +			read_val = 0x00010014;
> +			break;
> +		case 0xc0:
> +			/* DW2 for type-1 */
> +			read_val = 0x00000000;
> +			break;
> +		case 0xc4:
> +			/* Entry BEI=0, PP=0x00, SP=0xff, ES=3 */
> +			read_val = 0x80ff0003;
> +			break;
> +		case 0xc8:
> +			read_val = pem_pci->ea_entry[0];
> +			break;
> +		case 0xcc:
> +			read_val = pem_pci->ea_entry[1];
> +			break;
> +		case 0xd0:
> +			read_val = pem_pci->ea_entry[2];
> +			break;
> +		default:
> +			break;
> +		}
> +		read_val >>= (8 * (where & 3));
> +		switch (size) {
> +		case 1:
> +			read_val &= 0xff;
> +			break;
> +		case 2:
> +			read_val &= 0xffff;
> +			break;
> +		default:
> +			break;
> +		}
> +		*val = read_val;
> +		return PCIBIOS_SUCCESSFUL;
> +	}
> +	if (bus->number < pci->cfg.bus_range->start ||
> +	    bus->number > pci->cfg.bus_range->end)
> +		return PCIBIOS_DEVICE_NOT_FOUND;
> +
> +	r = pci_generic_config_read(bus, devfn, where, size, val);
> +	return r;
> +}
> +
> +static int thunder_pem_config_write(struct pci_bus *bus, unsigned int devfn,
> +				    int where, int size, u32 val)
> +{
> +	struct gen_pci *pci = bus->sysdata;
> +	struct thunder_pem_pci *pem_pci;
> +
> +	pem_pci = container_of(pci, struct thunder_pem_pci, gen_pci);
> +
> +	/*
> +	 * The first device on the bus in the PEM PCIe bridge.
> +	 * Special case its config access.
> +	 */
> +	if (bus->number == pci->cfg.bus_range->start) {
> +		u64 write_val, read_val;
> +
> +		if (devfn != 0 || where >= 2048)
> +			return PCIBIOS_DEVICE_NOT_FOUND;
> +
> +		/*
> +		 * 32-bit accesses only.  If the write is for a size
> +		 * smaller than 32-bits, we must first read the 32-bit
> +		 * value and merge in the desired bits and then write
> +		 * the whole 32-bits back out.
> +		 */

Ugh.  Another device that only supports 32-bit writes.  I guess this
only affects this single device, and maybe you "know" that it has no
registers where RW1C bits may be corrupted.  Although I suppose this
device has the standard status registers (Status at 0x06, Secondary
Status at 0x1e, Device Status in PCIe capability, etc.), which do
contain RW1C bits.

We need to print a warning at probe-time so we know to consider the
possibility of corruption when debugging.

> +		switch (size) {
> +		case 1:
> +			read_val = where & ~3ull;
> +			writeq(read_val, pem_pci->pem_reg_base + PEM_CFG_RD);
> +			read_val = readq(pem_pci->pem_reg_base + PEM_CFG_RD);
> +			read_val >>= 32;
> +			read_val &= ~(0xff << (8 * (where & 3)));
> +			val = (val & 0xff) << (8 * (where & 3));
> +			val |= (u32)read_val;
> +			break;
> +		case 2:
> +			read_val = where & ~3ull;
> +			writeq(read_val, pem_pci->pem_reg_base + PEM_CFG_RD);
> +			read_val = readq(pem_pci->pem_reg_base + PEM_CFG_RD);
> +			read_val >>= 32;
> +			read_val &= ~(0xffff << (8 * (where & 3)));
> +			val = (val & 0xffff) << (8 * (where & 3));
> +			val |= (u32)read_val;
> +			break;
> +		default:
> +			break;
> +
> +		}
> +		/*
> +		 * Low order bits are the config address, the high
> +		 * order 32 bits are the data to be written.
> +		 */
> +		write_val = where & ~3ull;
> +		write_val |= (((u64)val) << 32);
> +		writeq(write_val, pem_pci->pem_reg_base + PEM_CFG_WR);
> +		return PCIBIOS_SUCCESSFUL;
> +	}
> +	if (bus->number < pci->cfg.bus_range->start ||
> +	    bus->number > pci->cfg.bus_range->end)
> +		return PCIBIOS_DEVICE_NOT_FOUND;
> +	return pci_generic_config_write(bus, devfn, where, size, val);
> +}
> +
> +static void __iomem *map_cfg_bus_thunder_pem(struct pci_bus *bus,
> +					     unsigned int devfn,
> +					     int where)
> +{
> +	struct gen_pci *pci = bus->sysdata;
> +	resource_size_t idx = bus->number - pci->cfg.bus_range->start;
> +
> +	return pci->cfg.win[idx] + ((devfn << 16) | where);
> +}
> +
> +static struct gen_pci_cfg_bus_ops thunder_pem_bus_ops = {
> +	.bus_shift	= 24,
> +	.ops		= {
> +		.map_bus	= map_cfg_bus_thunder_pem,

How about "thunder_pem_map_bus"?

> +		.read		= thunder_pem_config_read,
> +		.write		= thunder_pem_config_write,
> +	}
> +};
> +
> +static const struct of_device_id thunder_pem_of_match[] = {
> +	{ .compatible = "cavium,pci-host-thunder-pem",
> +	  .data = &thunder_pem_bus_ops },
> +
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, thunder_pem_of_match);
> +
> +static int thunder_pem_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	const struct of_device_id *of_id;
> +	resource_size_t bar4_start;
> +	struct resource *res_pem;
> +	struct thunder_pem_pci *pem_pci;
> +
> +	pem_pci = devm_kzalloc(dev, sizeof(*pem_pci), GFP_KERNEL);
> +	if (!pem_pci)
> +		return -ENOMEM;
> +
> +	of_id = of_match_node(thunder_pem_of_match, dev->of_node);
> +	pem_pci->gen_pci.cfg.ops = (struct gen_pci_cfg_bus_ops *)of_id->data;
> +
> +	/*
> +	 * The second register range is the PEM bridge to the PCIe
> +	 * bus.  It has a different config access method than those
> +	 * devices behind the bridge.
> +	 */
> +	res_pem = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> +	if (!res_pem) {
> +		dev_err(dev, "missing \"reg[1]\"property\n");
> +		return -EINVAL;
> +	}
> +
> +	pem_pci->pem_reg_base = devm_ioremap(dev, res_pem->start, 0x10000);
> +	if (!pem_pci->pem_reg_base)
> +		return -ENOMEM;
> +
> +	/*
> +	 * The MSI-X BAR for the PEM and AER interrupts is located at
> +	 * a fixed offset from the PEM register base.  Generate a
> +	 * fragment of the synthesized Enhanced Allocation capability
> +	 * structure here for the BAR.
> +	 */
> +	bar4_start = res_pem->start + 0xf00000;
> +	pem_pci->ea_entry[0] = (u32)bar4_start | 2;
> +	pem_pci->ea_entry[1] = (u32)(res_pem->end - bar4_start) & ~3u;
> +	pem_pci->ea_entry[2] = (u32)(bar4_start >> 32);
> +
> +	return pci_host_common_probe(pdev, &pem_pci->gen_pci);
> +}
> +
> +static struct platform_driver thunder_pem_driver = {
> +	.driver = {
> +		.name = KBUILD_MODNAME,
> +		.of_match_table = thunder_pem_of_match,
> +	},
> +	.probe = thunder_pem_probe,
> +};
> +module_platform_driver(thunder_pem_driver);
> +
> +MODULE_DESCRIPTION("Thunder PEM PCIe host driver");
> +MODULE_LICENSE("GPL v2");
> -- 
> 1.8.3.1
> 
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