Re: [PATCH 3/6] x86, acpi, pci: Move PCI config space accessors.

[Tomasz Nowicki <tomasz.nowicki@linaro.org>]

On 11.12.2014 00:17, Bjorn Helgaas wrote:
> On Wed, Nov 19, 2014 at 05:04:48PM +0100, Tomasz Nowicki wrote:
>> We are going to use mmio_config_{} name convention across all architectures.
>
> mmio_config_*() are workarounds for an AMD Fam10h defect [1].  I would prefer
> not to extend these names to other architectures, because they should be
> able to use readb()/writeb()/etc. directly, as we did on x86 before
> 3320ad994afb ("x86: Work around mmio config space quirk on AMD Fam10h").
>
> In fact, it would be nice if we could use readb()/writeb()/etc. on x86, and
> only use mmio_config_*() when we're on AMD Fam10h.  Maybe there could be a
> "struct pci_raw_ops pci_mmcfg_amd_fam10h" that used mmio_config_*(), and we
> could set raw_pci_ext_ops to those ops instead of the default ones when
> we're on AMD Fam10h.  Then x86 should be able to use the generic
> readb()-based ops on most platforms.

While I do agree we should use readb()/writeb()... methods, I am not 
sure there is a nice way to use mmio_config_*() exclusively for AMD 
Fam10h. For x86, right now, we have three PCI config accessors sets: 
mmconfig_32.c, mmconfig_64.c, numachip.c and each are different. So one 
pci_mmcfg_amd_fam10h pci_raw_ops is not enough. I am thinking of having 
additional structure (integrated with "struct pci_mmcfg_region") that 
keeps MMIO accessors where readb()/writeb() would be the default one. 
For AMD Fam10h case we could tweak it as necessary. What do you thing Bjorn?

Tomasz

>
> Bjorn
>
> [1] 3320ad994afb ("x86: Work around mmio config space quirk on AMD Fam10h")
>
> Somewhere in this process, I'd like to update the AMD Fam10h comment to fix
> the typos and reference the spec that talks about this, i.e., the "BIOS and
> Kernel Developer's Guide (BKDG) For AMD Family 10h Processors," rev 3.48,
> sec 2.11.1, "MMIO Configuration Coding Requirements."
>
> That can be a separate patch since it's only cosmetic.
>
>> Currently it belongs to asm/pci_x86.h header which should be included
>> only for x86 specific files. From now on, those accessors are in asm/pci.h
>> header which can be included in non-architecture code much easier.
>>
>> Signed-off-by: Tomasz Nowicki <tomasz.nowicki@linaro.org>
>> Tested-by: Hanjun Guo <hanjun.guo@linaro.org>
>> ---
>>   arch/x86/include/asm/pci.h     | 42 +++++++++++++++++++++++++++++++++++++++++
>>   arch/x86/include/asm/pci_x86.h | 43 ------------------------------------------
>>   2 files changed, 42 insertions(+), 43 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/pci.h b/arch/x86/include/asm/pci.h
>> index 0892ea0..5ba3720 100644
>> --- a/arch/x86/include/asm/pci.h
>> +++ b/arch/x86/include/asm/pci.h
>> @@ -71,6 +71,48 @@ void pcibios_set_master(struct pci_dev *dev);
>>   struct irq_routing_table *pcibios_get_irq_routing_table(void);
>>   int pcibios_set_irq_routing(struct pci_dev *dev, int pin, int irq);
>>
>> +/*
>> + * AMD Fam10h CPUs are buggy, and cannot access MMIO config space
>> + * on their northbrige except through the * %eax register. As such, you MUST
>> + * NOT use normal IOMEM accesses, you need to only use the magic mmio-config
>> + * accessor functions.
>> + * In fact just use pci_config_*, nothing else please.
>> + */
>> +static inline unsigned char mmio_config_readb(void __iomem *pos)
>> +{
>> +	u8 val;
>> +	asm volatile("movb (%1),%%al" : "=a" (val) : "r" (pos));
>> +	return val;
>> +}
>> +
>> +static inline unsigned short mmio_config_readw(void __iomem *pos)
>> +{
>> +	u16 val;
>> +	asm volatile("movw (%1),%%ax" : "=a" (val) : "r" (pos));
>> +	return val;
>> +}
>> +
>> +static inline unsigned int mmio_config_readl(void __iomem *pos)
>> +{
>> +	u32 val;
>> +	asm volatile("movl (%1),%%eax" : "=a" (val) : "r" (pos));
>> +	return val;
>> +}
>> +
>> +static inline void mmio_config_writeb(void __iomem *pos, u8 val)
>> +{
>> +	asm volatile("movb %%al,(%1)" : : "a" (val), "r" (pos) : "memory");
>> +}
>> +
>> +static inline void mmio_config_writew(void __iomem *pos, u16 val)
>> +{
>> +	asm volatile("movw %%ax,(%1)" : : "a" (val), "r" (pos) : "memory");
>> +}
>> +
>> +static inline void mmio_config_writel(void __iomem *pos, u32 val)
>> +{
>> +	asm volatile("movl %%eax,(%1)" : : "a" (val), "r" (pos) : "memory");
>> +}
>>
>>   #define HAVE_PCI_MMAP
>>   extern int pci_mmap_page_range(struct pci_dev *dev, struct vm_area_struct *vma,
>> diff --git a/arch/x86/include/asm/pci_x86.h b/arch/x86/include/asm/pci_x86.h
>> index caba141..42e7332 100644
>> --- a/arch/x86/include/asm/pci_x86.h
>> +++ b/arch/x86/include/asm/pci_x86.h
>> @@ -121,49 +121,6 @@ extern int __init pcibios_init(void);
>>   extern int pci_legacy_init(void);
>>   extern void pcibios_fixup_irqs(void);
>>
>> -/*
>> - * AMD Fam10h CPUs are buggy, and cannot access MMIO config space
>> - * on their northbrige except through the * %eax register. As such, you MUST
>> - * NOT use normal IOMEM accesses, you need to only use the magic mmio-config
>> - * accessor functions.
>> - * In fact just use pci_config_*, nothing else please.
>> - */
>> -static inline unsigned char mmio_config_readb(void __iomem *pos)
>> -{
>> -	u8 val;
>> -	asm volatile("movb (%1),%%al" : "=a" (val) : "r" (pos));
>> -	return val;
>> -}
>> -
>> -static inline unsigned short mmio_config_readw(void __iomem *pos)
>> -{
>> -	u16 val;
>> -	asm volatile("movw (%1),%%ax" : "=a" (val) : "r" (pos));
>> -	return val;
>> -}
>> -
>> -static inline unsigned int mmio_config_readl(void __iomem *pos)
>> -{
>> -	u32 val;
>> -	asm volatile("movl (%1),%%eax" : "=a" (val) : "r" (pos));
>> -	return val;
>> -}
>> -
>> -static inline void mmio_config_writeb(void __iomem *pos, u8 val)
>> -{
>> -	asm volatile("movb %%al,(%1)" : : "a" (val), "r" (pos) : "memory");
>> -}
>> -
>> -static inline void mmio_config_writew(void __iomem *pos, u16 val)
>> -{
>> -	asm volatile("movw %%ax,(%1)" : : "a" (val), "r" (pos) : "memory");
>> -}
>> -
>> -static inline void mmio_config_writel(void __iomem *pos, u32 val)
>> -{
>> -	asm volatile("movl %%eax,(%1)" : : "a" (val), "r" (pos) : "memory");
>> -}
>> -
>>   #ifdef CONFIG_PCI
>>   # ifdef CONFIG_ACPI
>>   #  define x86_default_pci_init		pci_acpi_init
>> --
>> 1.9.1
>>