[PATCH v3] ARM: l2c: add options to overwrite prefetching behavior

[Russell King - ARM Linux]

On Fri, May 29, 2015 at 07:33:33PM +0200, Hauke Mehrtens wrote:
> Will this make it into kernel 4.2 or do I have to do something so that
> this will make it into 4.2?

I don't see anything wrong with it, but as ever, it needs to end up in the
patch system if it's not going to get buried beneath a huge pile of email.

Thanks.

> 
> Hauke
> 
> On 05/15/2015 11:52 PM, Hauke Mehrtens wrote:
> > These options make it possible to overwrites the data and instruction
> > prefetching behavior of the arm pl310 cache controller.
> > 
> > Signed-off-by: Hauke Mehrtens <hauke at hauke-m.de>
> > ---
> > v2: only set prefetch
> > v1: set prefetch and aux
> > 
> >  Documentation/devicetree/bindings/arm/l2cc.txt |  4 ++++
> >  arch/arm/mm/cache-l2x0.c                       | 20 ++++++++++++++++++++
> >  2 files changed, 24 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/arm/l2cc.txt b/Documentation/devicetree/bindings/arm/l2cc.txt
> > index 0dbabe9..528821a 100644
> > --- a/Documentation/devicetree/bindings/arm/l2cc.txt
> > +++ b/Documentation/devicetree/bindings/arm/l2cc.txt
> > @@ -67,6 +67,10 @@ Optional properties:
> >    disable if zero.
> >  - arm,prefetch-offset : Override prefetch offset value. Valid values are
> >    0-7, 15, 23, and 31.
> > +- arm,prefetch-data : Enable data prefetch. Enabling prefetching
> > +  can improve performance.
> > +- arm,prefetch-instr : Enable instruction prefetch. Enabling prefetching
> > +  can improve performance.
> >  
> >  Example:
> >  
> > diff --git a/arch/arm/mm/cache-l2x0.c b/arch/arm/mm/cache-l2x0.c
> > index e309c8f..1aa970a 100644
> > --- a/arch/arm/mm/cache-l2x0.c
> > +++ b/arch/arm/mm/cache-l2x0.c
> > @@ -1199,6 +1199,26 @@ static void __init l2c310_of_parse(const struct device_node *np,
> >  		pr_err("L2C-310 OF arm,prefetch-offset property value is missing\n");
> >  	}
> >  
> > +	ret = of_property_read_u32(np, "arm,prefetch-data", &val);
> > +	if (ret == 0) {
> > +		if (val)
> > +			prefetch |= L310_PREFETCH_CTRL_DATA_PREFETCH;
> > +		else
> > +			prefetch &= ~L310_PREFETCH_CTRL_DATA_PREFETCH;
> > +	} else if (ret != -EINVAL) {
> > +		pr_err("L2C-310 OF arm,prefetch-data property value is missing\n");
> > +	}
> > +
> > +	ret = of_property_read_u32(np, "arm,prefetch-instr", &val);
> > +	if (ret == 0) {
> > +		if (val)
> > +			prefetch |= L310_PREFETCH_CTRL_INSTR_PREFETCH;
> > +		else
> > +			prefetch &= ~L310_PREFETCH_CTRL_INSTR_PREFETCH;
> > +	} else if (ret != -EINVAL) {
> > +		pr_err("L2C-310 OF arm,prefetch-instr property value is missing\n");
> > +	}
> > +
> >  	l2x0_saved_regs.prefetch_ctrl = prefetch;
> >  }
> >  
> > 

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