linux-kernel - Re: [RFC PATCH V2 1/3] PCI: hisi: re-architect Hip05/Hip06 controllers driver to preapare for ACPI

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Date:   Wed, 31 Aug 2016 13:45:24 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Dongdong Liu <liudongdong3@...wei.com>
Cc:     helgaas@...nel.org, rafael@...nel.org, Lorenzo.Pieralisi@....com,
        tn@...ihalf.com, wangzhou1@...ilicon.com, pratyush.anand@...il.com,
        linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, jcm@...hat.com,
        gabriele.paoloni@...wei.com, charles.chenxin@...wei.com,
        hanjun.guo@...aro.org, linuxarm@...wei.com
Subject: Re: [RFC PATCH V2 1/3] PCI: hisi: re-architect Hip05/Hip06 controllers driver to preapare for ACPI

On Wednesday, August 31, 2016 7:48:12 PM CEST Dongdong Liu wrote:
> +
> +/* HipXX PCIe host only supports 32-bit config access */
> +int hisi_pcie_common_cfg_read(void __iomem *reg_base, int where, int size,
> +                             u32 *val)
> +{
> +       u32 reg;
> +       u32 reg_val;
> +       void *walker = &reg_val;
> +
> +       walker += (where & 0x3);
> +       reg = where & ~0x3;
> +       reg_val = readl(reg_base + reg);
> +
> +       if (size == 1)
> +               *val = *(u8 __force *) walker;
> +       else if (size == 2)
> +               *val = *(u16 __force *) walker;

What is the __force for?

> +       else if (size == 4)
> +               *val = reg_val;
> +       else
> +               return PCIBIOS_BAD_REGISTER_NUMBER;
> +
> +       return PCIBIOS_SUCCESSFUL;

It looks like you are reimplementing pci_generic_config_read32/pci_generic_config_write32
read here, better use them directly.

	Arnd