Re: [PATCH 1/3] pci: determine CLS more intelligently

[Ingo Molnar]

* Tejun Heo <tj@xxxxxxxxxx> 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.
> 
> While at it, declare pci_cache_line_size and 
> pci_dfl_cache_line_size in pci.h and drop private declarations 
> from arch code.
> 
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
> Acked-by: David Miller <davem@xxxxxxxxxxxxx>
> Acked-by: Greg KH <gregkh@xxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Tony Luck <tony.luck@xxxxxxxxx>

The principle looks good to me. Regressions could be expected though 
- these details are fragile and affect the way how we talk to 
hardware.

Acked-by: Ingo Molnar <mingo@xxxxxxx>

	Ingo
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