Subject: [PATCH] Revert "ARM: cns3xxx: pci: avoid potential stack overflow"

From: [email-masked] (Bjorn Helgaas)
Date: Tue, 31 May 2016 17:02:24 -0500

[+cc Russell, linux-arm-kernel]

On Tue, May 31, 2016 at 04:58:02PM -0500, Bjorn Helgaas wrote:
> This reverts commit 498a92d42596a7a32c042319eb62a4c3d8081cf1.
> 
> Krzysztof reported that this change broke Cavium CNS3xxx, ARMv6 (Laguna
> GW-2388) because the MRRS setting is never written to the hardware.

Krzysztof, can you test this and see whether it fixes the problem for
you?

> Signed-off-by: Bjorn Helgaas <[email-masked]>
> CC: Arnd Bergmann <[email-masked]>
> CC: Krzysztof Ha?asa <[email-masked]>
> ---
>  arch/arm/mach-cns3xxx/pcie.c |   71 ++++++++++++++++++++++++------------------
>  1 file changed, 41 insertions(+), 30 deletions(-)
> 
> diff --git a/arch/arm/mach-cns3xxx/pcie.c b/arch/arm/mach-cns3xxx/pcie.c
> index 318394e..c622c30 100644
> --- a/arch/arm/mach-cns3xxx/pcie.c
> +++ b/arch/arm/mach-cns3xxx/pcie.c
> @@ -65,9 +65,8 @@ static void __iomem *cns3xxx_pci_map_bus(struct pci_bus *bus,
>  
>  	/*
>  	 * The CNS PCI bridge doesn't fit into the PCI hierarchy, though
> -	 * we still want to access it.
> -	 * We place the host bridge on bus 0, and the directly connected
> -	 * device on bus 1, slot 0.
> +	 * we still want to access it. For this to work, we must place
> +	 * the first device on the same bus as the CNS PCI bridge.
>  	 */
>  	if (busno == 0) { /* internal PCIe bus, host bridge device */
>  		if (devfn == 0) /* device# and function# are ignored by hw */
> @@ -212,46 +211,58 @@ static void __init cns3xxx_pcie_check_link(struct cns3xxx_pcie *cnspci)
>  	}
>  }
>  
> -static void cns3xxx_write_config(struct cns3xxx_pcie *cnspci,
> -					 int where, int size, u32 val)
> -{
> -	void __iomem *base = cnspci->host_regs + (where & 0xffc);
> -	u32 v;
> -	u32 mask = (0x1ull << (size * 8)) - 1;
> -	int shift = (where % 4) * 8;
> -
> -	v = readl_relaxed(base);
> -
> -	v &= ~(mask << shift);
> -	v |= (val & mask) << shift;
> -
> -	writel_relaxed(v, base);
> -	readl_relaxed(base);
> -}
> -
>  static void __init cns3xxx_pcie_hw_init(struct cns3xxx_pcie *cnspci)
>  {
> +	int port = cnspci->port;
> +	struct pci_sys_data sd = {
> +		.private_data = cnspci,
> +	};
> +	struct pci_bus bus = {
> +		.number = 0,
> +		.ops = &cns3xxx_pcie_ops,
> +		.sysdata = &sd,
> +	};
>  	u16 mem_base  = cnspci->res_mem.start >> 16;
>  	u16 mem_limit = cnspci->res_mem.end   >> 16;
>  	u16 io_base   = cnspci->res_io.start  >> 16;
>  	u16 io_limit  = cnspci->res_io.end    >> 16;
> +	u32 devfn = 0;
> +	u8 tmp8;
> +	u16 pos;
> +	u16 dc;
> +
> +	pci_bus_write_config_byte(&bus, devfn, PCI_PRIMARY_BUS, 0);
> +	pci_bus_write_config_byte(&bus, devfn, PCI_SECONDARY_BUS, 1);
> +	pci_bus_write_config_byte(&bus, devfn, PCI_SUBORDINATE_BUS, 1);
>  
> -	cns3xxx_write_config(cnspci, PCI_PRIMARY_BUS, 1, 0);
> -	cns3xxx_write_config(cnspci, PCI_SECONDARY_BUS, 1, 1);
> -	cns3xxx_write_config(cnspci, PCI_SUBORDINATE_BUS, 1, 1);
> -	cns3xxx_write_config(cnspci, PCI_MEMORY_BASE, 2, mem_base);
> -	cns3xxx_write_config(cnspci, PCI_MEMORY_LIMIT, 2, mem_limit);
> -	cns3xxx_write_config(cnspci, PCI_IO_BASE_UPPER16, 2, io_base);
> -	cns3xxx_write_config(cnspci, PCI_IO_LIMIT_UPPER16, 2, io_limit);
> +	pci_bus_read_config_byte(&bus, devfn, PCI_PRIMARY_BUS, &tmp8);
> +	pci_bus_read_config_byte(&bus, devfn, PCI_SECONDARY_BUS, &tmp8);
> +	pci_bus_read_config_byte(&bus, devfn, PCI_SUBORDINATE_BUS, &tmp8);
> +
> +	pci_bus_write_config_word(&bus, devfn, PCI_MEMORY_BASE, mem_base);
> +	pci_bus_write_config_word(&bus, devfn, PCI_MEMORY_LIMIT, mem_limit);
> +	pci_bus_write_config_word(&bus, devfn, PCI_IO_BASE_UPPER16, io_base);
> +	pci_bus_write_config_word(&bus, devfn, PCI_IO_LIMIT_UPPER16, io_limit);
>  
>  	if (!cnspci->linked)
>  		return;
>  
>  	/* Set Device Max_Read_Request_Size to 128 byte */
> -	pcie_bus_config = PCIE_BUS_PEER2PEER;
> -
> +	bus.number = 1; /* directly connected PCIe device */
> +	devfn = PCI_DEVFN(0, 0);
> +	pos = pci_bus_find_capability(&bus, devfn, PCI_CAP_ID_EXP);
> +	pci_bus_read_config_word(&bus, devfn, pos + PCI_EXP_DEVCTL, &dc);
> +	if (dc & PCI_EXP_DEVCTL_READRQ) {
> +		dc &= ~PCI_EXP_DEVCTL_READRQ;
> +		pci_bus_write_config_word(&bus, devfn, pos + PCI_EXP_DEVCTL, dc);
> +		pci_bus_read_config_word(&bus, devfn, pos + PCI_EXP_DEVCTL, &dc);
> +		if (dc & PCI_EXP_DEVCTL_READRQ)
> +			pr_warn("PCIe: Unable to set device Max_Read_Request_Size\n");
> +		else
> +			pr_info("PCIe: Max_Read_Request_Size set to 128 bytes\n");
> +	}
>  	/* Disable PCIe0 Interrupt Mask INTA to INTD */
> -	__raw_writel(~0x3FFF, MISC_PCIE_INT_MASK(cnspci->port));
> +	__raw_writel(~0x3FFF, MISC_PCIE_INT_MASK(port));
>  }
>  
>  static int cns3xxx_pcie_abort_handler(unsigned long addr, unsigned int fsr,
> 
> --
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