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

Dongdong Liu
2016-09-01T02:06:27Z

在 2016/8/31 19:45, Arnd Bergmann 写道:
> 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?

Hi Arnd, thanks for replying.

__force is used to, well, force a conversion, like casting from or to a bitwise type, else the Sparse checker will throw a warning.

>
>> + 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.
>

For our host bridge, access RC and EP config space are not the same way.
Our host bridge is non ECAM only for the RC bus config space;
for any other bus underneath the root bus we support ECAM access.

hisi_pcie_common_cfg_read is used to read RC config space, only supports 32-bit config access.
hisi_pcie_common_cfg_read/hisi_pcie_common_cfg_write may change as below will be better.

/* 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)
{
void __iomem *addr;

addr = reg_base + (where & ~0x3);
*val = readl(addr);

if (size <= 2)
*val = (*val >> (8 * (where & 3))) & ((1 << (size * 8)) - 1);

return PCIBIOS_SUCCESSFUL;
}

/* HipXX PCIe host only supports 32-bit config access */
int hisi_pcie_common_cfg_write(void __iomem *reg_base, int where, int size,
u32 val)
{
void __iomem *addr;
u32 mask, tmp;

addr = reg_base + (where & ~0x3);
if (size == 4) {
writel(val, addr);
return PCIBIOS_SUCCESSFUL;
} else {
mask = ~(((1 << (size * 8)) - 1) << ((where & 0x3) * 8));
}

tmp = readl(addr) & mask;
tmp |= val << ((where & 0x3) * 8);
writel(tmp, addr);

return PCIBIOS_SUCCESSFUL;
}

Thanks
Dongdong

> Arnd
>
> .
>