On 05/29/2015 08:35 PM, Florian Fainelli wrote: > On 29/05/15 11:30, Florian Fainelli wrote: >> On 29/05/15 11:11, Hauke Mehrtens wrote: >>> >>> >>> On 05/29/2015 07:52 PM, Florian Fainelli wrote: >>>> On 15/05/15 14:52, 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@xxxxxxxxxx> >>>>> --- >>>>> 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. >>>> >>>> I do not think the "can improve performance" has a place in a binding, >>>> this is either not technical enough about what this does, or marketing >>>> enough it does not buy us much. >>>> >>>> data/instruction pre-fetching are commonly found on cache controller >>>> these days, so I would be tempted to remove the "arm," prefixing here >>>> since this can be generalized to other kinds of cache controllers. >>>> Documenting that this can be either a boolean, or accept a value (see >>>> below) could help. >>> >>> So you think I should only add prefetch-data and prefetch-instr without >>> the arm prefix. >> >> That's what I think yes, others may disagree. Are there any other opinions on this issue? >> >>>> >>>>> +- 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"); >>>>> + } >>>> >>>> If we want to generalize the use of this property, there could indeed be >>>> a value associated with it, if the cache controller supports different >>>> pre-fetching strides, however this is not the cache for these cache >>>> controllers it seems, are not we going to show error messages more often >>>> than desired? >>> I did this so it is possible to deactivate the prefech mode. I do not >>> know if somebody wants to do that. I haven't understood how you suggest >>> I should change. >>> When you do not associate a value with an entry in device tree it is >>> there or not there, so we could only activate it when it was not >>> automatically detected, but we could not deactivate it, because the case >>> when this value is not specified in device tree would be, use to auto >>> detected the value. >> >> My point is that you use of_read_property_u32, but your example does not >> state what should be the value associated with this property in the >> binding, so it is unclear what are the results without looking at the >> code between these examples: >> >> /* Enable data pre-fetching */ >> #1 arm,data-prefetch; >> #2 arm,data-prefetch = <1>; >> >> /* Disable data pre-fetching */ >> #3 arm,data-prefetch = <0>; >> >> /* do nothing, empty aka retain existing settings set by firmware */ >> #4 >> >> Based on the code, only #2 and #3 are intended, which raises the >> question, do not we want of_read_property_bool() instead then? The >> binding does seem to suggest that only #1 and #4 are valid though. > > I re-read the code, and I think if you just clarify the values in the > binding to be: 0 (forcibly disable), 1 (forcibly enable), property > absent (retain settings), this would be crystal clear. Ok I will do that. Hauke -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html