Message-Id: <201401031307.50312.arnd@arndb.de>
Date:	Fri, 3 Jan 2014 13:07:50 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Tanmay Inamdar <tinamdar@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Grant Likely <grant.likely@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Rob Landley <rob@...dley.net>, devicetree@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-pci@...r.kernel.org,
	patches@....com, linux-kernel@...r.kernel.org, jcm@...hat.com
Subject: Re: [RFC PATCH 1/3] pci: APM X-Gene PCIe controller driver

On Monday 23 December 2013, Tanmay Inamdar wrote:
> This patch adds the AppliedMicro X-gene SOC PCIe controller driver.
> APM X-Gene PCIe controller supports maximum upto 8 lanes and
> GEN3 speed. X-Gene has maximum 5 PCIe ports supported.
> 
> Signed-off-by: Tanmay Inamdar <tinamdar@....com>
> ---
>  drivers/pci/host/Kconfig      |    5 +
>  drivers/pci/host/Makefile     |    1 +
>  drivers/pci/host/pcie-xgene.c | 1017 +++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 1023 insertions(+)
>  create mode 100644 drivers/pci/host/pcie-xgene.c
> 
> diff --git a/drivers/pci/host/Kconfig b/drivers/pci/host/Kconfig
> index 47d46c6..6d8fcbc 100644
> --- a/drivers/pci/host/Kconfig
> +++ b/drivers/pci/host/Kconfig
> @@ -33,4 +33,9 @@ config PCI_RCAR_GEN2
>  	  There are 3 internal PCI controllers available with a single
>  	  built-in EHCI/OHCI host controller present on each one.
>  
> +config PCI_XGENE
> +	bool "X-Gene PCIe controller"
> +	depends on ARCH_XGENE
> +	depends on OF

Please add a help text here.

> +#ifdef CONFIG_ARM64
> +#include <asm/pcibios.h>
> +#else
> +#include <asm/mach/pci.h>
> +#endif

What is !ARM64 case? Is this for PowerPC or ARM? Since you depend on
ARCH_XGENE in Kconfig I guess neither case can actually happen,
so you can remove the #ifdef.

> +#define CFG_CONSTANTS_31_00		0x2000
> +#define CFG_CONSTANTS_63_32		0x2004
> +#define CFG_CONSTANTS_159_128		0x2010
> +#define CFG_CONSTANTS_415_384           0x2030

These macros do not seem helpful. If you don't have meaningful register
names, just don't provide any and address the registers by index.

> +#define ENABLE_L1S_POWER_MGMT_SET(dst, src)     (((dst) & ~0x02000000) | \
> +						(((u32)(src) << 0x19) & \
> +						0x02000000))

Makes this an inline function, or open-code it in the caller if there
is only one.

> +#ifdef CONFIG_64BIT
> +#define pci_io_offset(s)		(s & 0xff00000000)
> +#else
> +#define pci_io_offset(s)		(s & 0x00000000)
> +#endif /* CONFIG_64BIT */

Why is this needed? The I/O space can never be over 0xffffffff,
or in practice 0xffff. My best guess is that you have a bug in the
function parsing your ranges property, or in the property value.

> +static inline struct xgene_pcie_port *
> +xgene_pcie_sys_to_port(struct pci_sys_data *sys)
> +{
> +	return (struct xgene_pcie_port *)sys->private_data;
> +}

You shouldn't need the cast, or the accessor function, since private_data
is already a void pointer.

> +/* IO ports are memory mapped */
> +void __iomem *__pci_ioport_map(struct pci_dev *dev, unsigned long port,
> +			       unsigned int nr)
> +{
> +	return devm_ioremap_nocache(&dev->dev, port, nr);
> +}

This can't be in the host driver, since you can have only one instance
of the function in the system, but you probably want multiple host
drivers in a multiplatform kernel on ARM64.

Also, the implementation is wrong since the I/O port range already needs
to be ioremapped in order for inb/outb to work. There is already a
generic implementation of this in include/asm-generic/iomap.h, which
correctly calls ioport_map. Make sure that arm64 uses this implementation
and provides an ioport_map() function like

static inline void __iomem *ioport_map(unsigned long port, unsigned int nr)
{
	return PCI_IOBASE + port;
}

> +/* PCIE Out/In to CSR */
> +static inline void xgene_pcie_out32(void *addr, u32 val)
> +{
> +	pr_debug("pcie csr wr: 0x%llx 0x%08x\n", (phys_addr_t)addr, val);
> +	writel(val, addr);
> +}
> +
> +static inline void xgene_pcie_in32(void *addr, u32 *val)
> +{
> +	*val = readl(addr);
> +	pr_debug("pcie csr rd: 0x%llx 0x%08x\n", (phys_addr_t)addr, *val);
> +}

These add no value, just remove them. If your code is so buggy that
you need to print every register access to the debug log, we don't
want it ;-)

> +static inline void xgene_pcie_cfg_out16(void *addr, u16 val)
> +{
> +	phys_addr_t temp_addr = (phys_addr_t) addr & ~0x3;
> +	u32 val32 = readl((void *)temp_addr);
> +
> +	switch ((phys_addr_t) addr & 0x3) {
> +	case 2:
> +		val32 &= ~0xFFFF0000;
> +		val32 |= (u32) val << 16;
> +		break;
> +	case 0:
> +	default:
> +		val32 &= ~0xFFFF;
> +		val32 |= val;
> +		break;
> +	}
> +	writel(val32, (void *)temp_addr);
> +}

Isn't there a generic version of this? If not, should there be one?
Maybe Bjorn can comment.

Also, all the typecasts are wrong. Please think about what types
you really want and fix them.

> +static void xgene_pcie_set_rtdid_reg(struct pci_bus *bus, uint devfn)
> +{
> +	struct xgene_pcie_port *port = xgene_pcie_bus_to_port(bus);
> +	unsigned int b, d, f;
> +	u32 rtdid_val = 0;
> +
> +	b = bus->number;
> +	d = PCI_SLOT(devfn);
> +	f = PCI_FUNC(devfn);
> +
> +	if (bus->number == port->first_busno)
> +		rtdid_val = (b << 24) | (d << 19) | (f << 16);
> +	else if (bus->number >= (port->first_busno + 1))
> +		rtdid_val = (port->first_busno << 24) |
> +		(b << 8) | (d << 3) | f;
> +
> +	xgene_pcie_out32(port->csr_base + RTDID, rtdid_val);
> +	/* read the register back to ensure flush */
> +	xgene_pcie_in32(port->csr_base + RTDID, &rtdid_val);
> +}

What is an 'rtdid'? Maybe add some comments

> +static void xgene_pcie_setup_lanes(struct xgene_pcie_port *port)
> +{
> +	void *csr_base = port->csr_base;
> +	u32 val;
> +
...
> +static void xgene_pcie_setup_link(struct xgene_pcie_port *port)
> +{
> +	void *csr_base = port->csr_base;
> +	u32 val;
> +

Don't these belong into the PHY driver? Can the setup be done in the
firmware instead so we don't have to bother with it in Linux?
Presumably you already need PCI support at boot time already if
you want to boot from a PCI device.

> +static void xgene_pcie_config_pims(void *csr_base, u32 addr,
> +				   u64 pim, resource_size_t size)
> +{
> +	u32 val;
> +
> +	xgene_pcie_out32(csr_base + addr, lower_32_bits(pim));
> +	val = upper_32_bits(pim) | EN_COHERENCY;
> +	xgene_pcie_out32(csr_base + addr + 0x04, val);
> +	xgene_pcie_out32(csr_base + addr + 0x08, 0x0);
> +	xgene_pcie_out32(csr_base + addr + 0x0c, 0x0);
> +	val = lower_32_bits(size);
> +	xgene_pcie_out32(csr_base + addr + 0x10, val);
> +	val = upper_32_bits(size);
> +	xgene_pcie_out32(csr_base + addr + 0x14, val);
> +}

I suspect this is for programming the inbound translation window for
DMA transactions (maybe add a comment?), and the second 64-bit word is
for the bus-side address. Are you sure you want a translation starting
at zero, rather than an identity-mapping like this?

	xgene_pcie_out32(csr_base + addr, lower_32_bits(pim));
	val = upper_32_bits(pim) | EN_COHERENCY;
	xgene_pcie_out32(csr_base + addr + 0x04, val);
	xgene_pcie_out32(csr_base + addr + 0x08, pim & 0xffffffff);
	xgene_pcie_out32(csr_base + addr + 0x0c, pim >> 32);

> +static void xgene_pcie_setup_port(struct xgene_pcie_port *port)
> +{
> +	int type = port->type;
> +
> +	xgene_pcie_program_core(port->csr_base);
> +	if (type == PTYPE_ROOT_PORT)
> +		xgene_pcie_setup_root_complex(port);
> +	else
> +		xgene_pcie_setup_endpoint(port);
> +}

We don't really have infrastructure for PCIe endpoint devices in Linux,
or in the generic DT binding for PCI hosts. We probably really want to
add that in the future, but until we have decided on how to do this,
please remove all code related to endpoint mode.

> +struct device_node *pcibios_get_phb_of_node(struct pci_bus *bus)
> +{
> +	struct xgene_pcie_port *port = xgene_pcie_bus_to_port(bus);
> +
> +	return of_node_get(port->node);
> +}

Another pointless wrapper to remove.

> +static void xgene_pcie_fixup_bridge(struct pci_dev *dev)
> +{
> +	int i;
> +
> +	for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {
> +		dev->resource[i].start = dev->resource[i].end = 0;
> +		dev->resource[i].flags = 0;
> +	}
> +}
> +DECLARE_PCI_FIXUP_HEADER(XGENE_PCIE_VENDORID, XGENE_PCIE_BRIDGE_DEVICEID,
> +			 xgene_pcie_fixup_bridge);

Please add a comment to describe exactly what bug you are working around,
and what devices are affected.

> +/*
> + * read configuration values from DTS
> + */
> +static int xgene_pcie_read_dts_config(struct xgene_pcie_port *port)
> +{
> +	struct device_node *np = port->node;
> +	struct resource csr_res;
> +	u32 val32;
> +	int ret;
> +	const u8 *val;
> +
> +	val = of_get_property(np, "device_type", NULL);
> +	if ((val != NULL) && !strcmp(val, "ep"))
> +		port->type = PTYPE_ENDPOINT;
> +	else
> +		port->type = PTYPE_ROOT_PORT;

"ep" is not a valid device_type for all I know.

> +	ret = of_property_read_u32(np, "link_speed", &val32);
> +	if (ret == 0)
> +		port->link_speed = val32;
> +	else
> +		port->link_speed = PCIE_GEN3;

I guess this should be an argument to the phy node. Isn't it the phy
that needs to know the link speed rather than the host?

> +static int xgene_pcie_alloc_ep_mem(struct xgene_pcie_port *port)
> +{
> +	struct xgene_pcie_ep_info *ep = &port->ep_info;
> +
> +	ep->reg_virt = dma_alloc_coherent(port->dev, XGENE_PCIE_EP_MEM_SIZE,
> +					  &ep->reg_phys, GFP_KERNEL);
> +	if (ep->reg_virt == NULL)
> +		return -ENOMEM;
> +
> +	dev_info(port->dev, "EP: Virt - %p Phys - 0x%llx Size - 0x%x\n",
> +		 ep->reg_virt, (u64) ep->reg_phys, XGENE_PCIE_EP_MEM_SIZE);
> +	return 0;
> +}

remove endpoint stuff for now.

> +static int xgene_pcie_populate_inbound_regions(struct xgene_pcie_port *port)
> +{
> +	struct resource *msi_res = &port->res[XGENE_MSI];
> +	phys_addr_t ddr_size = memblock_phys_mem_size();
> +	phys_addr_t ddr_base = memblock_start_of_DRAM();

This looks fragile. What about discontiguous memory? It's probably better to
leave this setup to the firmware, which already has to do it.

> +static int xgene_pcie_parse_map_ranges(struct xgene_pcie_port *port)
> +{
> +	struct device_node *np = port->node;
> +	struct of_pci_range range;
> +	struct of_pci_range_parser parser;
> +	struct device *dev = port->dev;
> +	u32 cfg_map_done = 0;
> +	int ret;
> +
> +	if (of_pci_range_parser_init(&parser, np)) {
> +		dev_err(dev, "missing ranges property\n");
> +		return -EINVAL;
> +	}
> +
> +	/* Get the I/O, memory, config ranges from DT */
> +	for_each_of_pci_range(&parser, &range) {
> +		struct resource *res = NULL;
> +		u64 restype = range.flags & IORESOURCE_TYPE_BITS;
> +		u64 end = range.cpu_addr + range.size - 1;
> +		dev_dbg(port->dev, "0x%08x 0x%016llx..0x%016llx -> 0x%016llx\n",
> +			range.flags, range.cpu_addr, end, range.pci_addr);
> +
> +		switch (restype) {
> +		case IORESOURCE_IO:
> +			res = &port->res[XGENE_IO];
> +			of_pci_range_to_resource(&range, np, res);
> +			xgene_pcie_setup_ob_reg(port->csr_base, OMR1BARL,
> +						XGENE_IO, res);
> +			break;
> +		case IORESOURCE_MEM:
> +			res = &port->res[XGENE_MEM];
> +			of_pci_range_to_resource(&range, np, res);
> +			xgene_pcie_setup_ob_reg(port->csr_base, OMR2BARL,
> +						XGENE_MEM, res);
> +			break;

You also need to read out the pci_addr field from the range struct in order
to set up the io_offset and mem_offset and the translation windows.
Don't assume that they start at zero.

> +		case 0:
> +			if (!cfg_map_done) {
> +				/* config region */
> +				if (port->type == PTYPE_ROOT_PORT) {
> +					ret = xgene_pcie_map_cfg(port, &range);
> +					if (ret)
> +						return ret;
> +				}
> +				cfg_map_done = 1;
> +			} else {
> +				/* msi region */
> +				res = &port->res[XGENE_MSI];
> +				of_pci_range_to_resource(&range, np, res);
> +			}
> +			break;

Don't make assumptions about the order of the ranges property. Also, neither
the MSI register nor the config space should be in the ranges.

> +static int xgene_pcie_setup(int nr, struct pci_sys_data *sys)
> +{
> +	struct xgene_pcie_port *pp = xgene_pcie_sys_to_port(sys);
> +
> +	if (pp == NULL)
> +		return 0;
> +
> +	if (pp->type == PTYPE_ENDPOINT)
> +		return 0;
> +
> +	sys->io_offset = pci_io_offset(pp->res[XGENE_IO].start);

Normally we want io_offset to be zero, i.e. have every Bus I/O space
window get translated to the same Linux I/O space address, i.e.
the number you pass into pci_ioremap_io(). The code here assumes
that the Bus I/O address is zero instead and the io_offset adjusts
for that, which is a bit confusing. Please change it to read
the actual values from the ranges property.

> +	sys->mem_offset = pci_io_offset(pp->res[XGENE_MEM].start);
> +
> +	BUG_ON(request_resource(&iomem_resource, &pp->res[XGENE_IO]) ||
> +	       request_resource(&iomem_resource, &pp->res[XGENE_MEM]));
> +
> +	pci_add_resource_offset(&sys->resources, &pp->res[XGENE_MEM],
> +				sys->mem_offset);
> +	pci_add_resource_offset(&sys->resources, &pp->res[XGENE_IO],
> +				sys->io_offset);

&pp->res[XGENE_IO] is in memory space, while the argument you want here
is in I/O space.

> +static int xgene_pcie_map_irq(const struct pci_dev *dev, u8 slot, u8 pin)
> +{
> +	return of_irq_parse_and_map_pci(dev, slot, pin);
> +}

Just use the function directly and remove the wrapper.

	Arnd
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