Re: [RFC PATCH 1/2] pci: determine CLS more intelligently

Benjamin Herrenschmidt
2009-06-25T10:09:33Z

On Thu, 2009-06-25 at 16:12 +0900, Tejun Heo wrote:
> Till now, CLS has been determined either by arch code or as
> L1_CACHE_BYTES. Only x86 and ia64 set CLS explicitly and x86 doesn't
> always get it right. On most configurations, the chance is that
> firmware configures the correct value during boot.
>
> This patch makes pci_init() determine CLS by looking at what firmware
> has configured. It scans all devices and if all non-zero values
> agree, the value is used. If none is configured or there is a
> disagreement, pci_dfl_cache_line_size is used. arch can set the dfl
> value (via PCI_CACHE_LINE_BYTES or pci_dfl_cache_line_size) or
> override the actual one.
>
> ia64, x86 and sparc64 updated to set the default cls instead of the
> actual one. sparc64 is currently the only one using
> PCI_CACHE_LINE_BYTES. It would be nice to update it to set the
> default variable instead.

Looks ok, I'll have a quick look through though, as we have some weirdo
stuff on some PowerMacs with both PCI/PCI-E and HT off the north bridge
who need different values behind those different segments (for strange
reasons). IIRC, We get away because we never enable MWI on these (ie, I
don't think your patch can cause a regression either way), but I suppose
it would be good if I double checked.

If you don't hear from me mid next week, assume I forgot and merge it,
I'll deal with the consequences :-)

Cheers,
Ben.

> RFC PATCH, PLEASE DON'T APPLY YET.
> Cc: Greg KH <gregkh@suse.de>
> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Tony Luck <tony.luck@intel.com>
> Cc: David Miller <davem@davemloft.net>
> ---
> These two patches are refreshed version of the following patch.
>
> http://thread.gmane.org/gmane.linux.kernel.pci/4418/focus=4431
>
> This patch improves how CLS is determined and was written mainly
> because the original code didn't get it right on my laptop (lenovo
> x61s, the determined value was 32 but the value bios used for other
> devices was 64). For x86, maybe we can remove the arch specific
> configuration codes in the long run?
>
> Seems to work fine on my test machine and laptop. Also builds fine
> for powerpc64 and sparc64.
>
> Axel, to test, you'll need to build a vanialla kernel with the patches
> applied. There are pretty good docs about doing that on the web.
>
> Thanks.
>
> arch/ia64/pci/pci.c | 8 ++++----
> arch/x86/pci/common.c | 8 ++++----
> drivers/pci/pci.c | 49 +++++++++++++++++++++++++++++++++++++++++--------
> 3 files changed, 49 insertions(+), 16 deletions(-)
>
> Index: work/arch/ia64/pci/pci.c
> ===================================================================
> --- work.orig/arch/ia64/pci/pci.c
> +++ work/arch/ia64/pci/pci.c
> @@ -716,7 +716,7 @@ int ia64_pci_legacy_write(struct pci_bus
> }
>
> /* It's defined in drivers/pci/pci.c */
> -extern u8 pci_cache_line_size;
> +extern u8 pci_dfl_cache_line_size;
>
> /**
> * set_pci_cacheline_size - determine cacheline size for PCI devices
> @@ -726,7 +726,7 @@ extern u8 pci_cache_line_size;
> *
> * Code mostly taken from arch/ia64/kernel/palinfo.c:cache_info().
> */
> -static void __init set_pci_cacheline_size(void)
> +static void __init set_pci_dfl_cacheline_size(void)
> {
> unsigned long levels, unique_caches;
> long status;
> @@ -746,7 +746,7 @@ static void __init set_pci_cacheline_siz
> "(status=%ld)\n", __func__, status);
> return;
> }
> - pci_cache_line_size = (1 << cci.pcci_line_size) / 4;
> + pci_dfl_cache_line_size = (1 << cci.pcci_line_size) / 4;
> }
>
> u64 ia64_dma_get_required_mask(struct device *dev)
> @@ -777,7 +777,7 @@ EXPORT_SYMBOL_GPL(dma_get_required_mask)
>
> static int __init pcibios_init(void)
> {
> - set_pci_cacheline_size();
> + set_pci_dfl_cacheline_size();
> return 0;
> }
>
> Index: work/arch/x86/pci/common.c
> ===================================================================
> --- work.orig/arch/x86/pci/common.c
> +++ work/arch/x86/pci/common.c
> @@ -410,7 +410,7 @@ struct pci_bus * __devinit pcibios_scan_
> return bus;
> }
>
> -extern u8 pci_cache_line_size;
> +extern u8 pci_dfl_cache_line_size;
>
> int __init pcibios_init(void)
> {
> @@ -426,11 +426,11 @@ int __init pcibios_init(void)
> * and P4. It's also good for 386/486s (which actually have 16)
> * as quite a few PCI devices do not support smaller values.
> */
> - pci_cache_line_size = 32 >> 2;
> + pci_dfl_cache_line_size = 32 >> 2;
> if (c->x86 >= 6 && c->x86_vendor == X86_VENDOR_AMD)
> - pci_cache_line_size = 64 >> 2; /* K7 & K8 */
> + pci_dfl_cache_line_size = 64 >> 2; /* K7 & K8 */
> else if (c->x86 > 6 && c->x86_vendor == X86_VENDOR_INTEL)
> - pci_cache_line_size = 128 >> 2; /* P4 */
> + pci_dfl_cache_line_size = 128 >> 2; /* P4 */
>
> pcibios_resource_survey();
>
> Index: work/drivers/pci/pci.c
> ===================================================================
> --- work.orig/drivers/pci/pci.c
> +++ work/drivers/pci/pci.c
> @@ -41,6 +41,19 @@ int pci_domains_supported = 1;
> unsigned long pci_cardbus_io_size = DEFAULT_CARDBUS_IO_SIZE;
> unsigned long pci_cardbus_mem_size = DEFAULT_CARDBUS_MEM_SIZE;
>
> +#ifndef PCI_CACHE_LINE_BYTES
> +#define PCI_CACHE_LINE_BYTES L1_CACHE_BYTES
> +#endif
> +
> +/*
> + * The default CLS is used if arch didn't set CLS explicitly and not
> + * all pci devices agree on the same value. Arch can override either
> + * the dfl or actual value as it sees fit. Don't forget this is
> + * measured in 32-bit words, not bytes.
> + */
> +u8 pci_dfl_cache_line_size __initdata = PCI_CACHE_LINE_BYTES >> 2;
> +u8 pci_cache_line_size;
> +
> /**
> * pci_bus_max_busnr - returns maximum PCI bus number of given bus' children
> * @bus: pointer to PCI bus structure to search
> @@ -1848,14 +1861,6 @@ void pci_clear_mwi(struct pci_dev *dev)
>
> #else
>
> -#ifndef PCI_CACHE_LINE_BYTES
> -#define PCI_CACHE_LINE_BYTES L1_CACHE_BYTES
> -#endif
> -
> -/* This can be overridden by arch code. */
> -/* Don't forget this is measured in 32-bit words, not bytes */
> -u8 pci_cache_line_size = PCI_CACHE_LINE_BYTES / 4;
> -
> /**
> * pci_set_cacheline_size - ensure the CACHE_LINE_SIZE register is programmed
> * @dev: the PCI device for which MWI is to be enabled
> @@ -2631,9 +2636,37 @@ int __attribute__ ((weak)) pci_ext_cfg_a
> static int __devinit pci_init(void)
> {
> struct pci_dev *dev = NULL;
> + u8 cls = 0;
> + u8 tmp;
> +
> + if (pci_cache_line_size)
> + printk(KERN_DEBUG "PCI: CLS %u bytes\n",
> + pci_cache_line_size << 2);
>
> while ((dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, dev)) != NULL) {
> pci_fixup_device(pci_fixup_final, dev);
> + /*
> + * If arch hasn't set it explicitly yet, use the CLS
> + * value shared by all PCI devices. If there's a
> + * mismatch, fall back to the default value.
> + */
> + if (!pci_cache_line_size) {
> + pci_read_config_byte(dev, PCI_CACHE_LINE_SIZE, &tmp);
> + if (!cls)
> + cls = tmp;
> + if (!tmp || cls == tmp)
> + continue;
> +
> + printk(KERN_DEBUG "PCI: CLS mismatch (%u != %u), "
> + "using %u bytes\n", cls << 2, tmp << 2,
> + pci_dfl_cache_line_size << 2);
> + pci_cache_line_size = pci_dfl_cache_line_size;
> + }
> + }
> + if (!pci_cache_line_size) {
> + printk(KERN_DEBUG "PCI: CLS %u bytes, default %u\n",
> + cls << 2, pci_dfl_cache_line_size << 2);
> + pci_cache_line_size = cls;
> }
>
> return 0;