> On Jul 2, 2015, at 11:49 AM, Luis R. Rodriguez wrote:
>
> On Sat, Jun 27, 2015 at 08:00:48AM +1000, Benjamin Herrenschmidt wrote:
>> On Fri, 2015-06-26 at 16:24 +, Casey Leedom wrote:
>>> Thanks for looking into this Ben. As it stands now, it seems as
>>> if Write Combined mappings simpl
On Thu, 2015-07-02 at 20:49 +0200, Luis R. Rodriguez wrote:
> > The question then is what is "the right thing". In the powerpc case,
> > we'll have a non-garded mapping, which means we also get no ordering
> > between load and stores.
>
> I don't follow, you *ordering* between load and stores for
On Sat, Jun 27, 2015 at 08:00:48AM +1000, Benjamin Herrenschmidt wrote:
> On Fri, 2015-06-26 at 16:24 +, Casey Leedom wrote:
> > Thanks for looking into this Ben. As it stands now, it seems as
> > if Write Combined mappings simply aren't supported and/or all
> > driver writers trying to util
On Fri, Jun 26, 2015 at 4:54 PM, Benjamin Herrenschmidt
wrote:
> On Fri, 2015-06-26 at 15:41 -0700, Luis R. Rodriguez wrote:
>
>> > It wasn't nullified for the main user at the time, the fb. And I
>> > mentioned an IB adapter or two for which the code had been hand
>> tuned.
>>
>> This still means
On Fri, 2015-06-26 at 15:41 -0700, Luis R. Rodriguez wrote:
> > It wasn't nullified for the main user at the time, the fb. And I
> > mentioned an IB adapter or two for which the code had been hand
> tuned.
>
> This still means there could be some affected drivers when used on
> powerpc, no?
Yes.
On Jun 26, 2015 3:05 PM, "Benjamin Herrenschmidt"
wrote:
>
> On Fri, 2015-06-26 at 21:31 +0200, Luis R. Rodriguez wrote:
> > > Yeah either, we need to fix our relaxed implementation (patch
> > > welcome :-)
> >
> > Yikes, so although powerpc has useful heuristics to automatically
> > enable WC the
On Fri, 2015-06-26 at 21:31 +0200, Luis R. Rodriguez wrote:
> > Yeah either, we need to fix our relaxed implementation (patch
> > welcome :-)
>
> Yikes, so although powerpc has useful heuristics to automatically
> enable WC the default write ops have been nullifying its effects?
The heuristic is
On Fri, 2015-06-26 at 16:24 +, Casey Leedom wrote:
> Thanks for looking into this Ben. As it stands now, it seems as
> if Write Combined mappings simply aren't supported and/or all
> driver writers trying to utilize Write Combined mappings have to
> "hand roll" their own solutions which real
On Fri, Jun 26, 2015 at 08:51:58AM +1000, Benjamin Herrenschmidt wrote:
> On Thu, 2015-06-25 at 21:40 +, Casey Leedom wrote:
> > Hhmmm, so what do PowerPC Drivers do when they want to take
> > advantage of Write Combining? Do their own Endian Swizzling
> > with the __raw_*() APIs?
>
> Yeah ei
Thanks for looking into this Ben. As it stands now, it seems as
if Write Combined mappings simply aren't supported and/or all
driver writers trying to utilize Write Combined mappings have to
"hand roll" their own solutions which really isn't supportable.
One thing that might be considered is
On Thu, 2015-06-25 at 21:40 +, Casey Leedom wrote:
>
> Ah, thanks. I see now that the __raw_*() APIs don't do any of the
> Endian Swizzling. Unfortunately the *_relaxed() APIs on PowerPC
> are just defined as the normal *() routines. From
> arch/powerpc/include/asm/io.h:
>
> /*
>
On Thu, 2015-06-25 at 21:40 +, Casey Leedom wrote:
> Hhmmm, so what do PowerPC Drivers do when they want to take
> advantage of Write Combining? Do their own Endian Swizzling
> with the __raw_*() APIs?
Yeah either, we need to fix our relaxed implementation (patch
welcome :-)
Cheers,
Ben.
| From: Arnd Bergmann [a...@arndb.de]
| Sent: Thursday, June 25, 2015 1:44 PM
|
| On Thursday 25 June 2015 15:01:56 Casey Leedom wrote:
| >
| > Is there a reference I can read on this so I can understand
| > when and where we can use the __raw_*() APIs? Can these
| > Raw Read/Write operations b
On Thursday 25 June 2015 15:01:56 Casey Leedom wrote:
>
> Is there a reference I can read on this so I can understand
> when and where we can use the __raw_*() APIs? Can these
> Raw Read/Write operations be reordered with respect to
> each other or are the use of the various flavors of SYNC
> i
/ From: Benjamin Herrenschmidt [b...@kernel.crashing.org]
| Sent: Wednesday, June 24, 2015 4:38 PM
|
| It is to be noted that on powerpc at least, writel() and co will never
| combine due to the memory barriers in them. Only "normal" stores (or
\ __raw_writel) will.
/ From: Benjamin Herrenschmidt
On Wed, 2015-06-24 at 17:58 -0700, Luis R. Rodriguez wrote:
> On Wed, Jun 24, 2015 at 5:52 PM, Benjamin Herrenschmidt
> wrote:
> > On Thu, 2015-06-25 at 02:08 +0200, Luis R. Rodriguez wrote:
> >>
> >> OK thanks I'll proceed with these patches then.
> >>
> >> > As for user mappings,
> >>
> >> Which
On Wed, Jun 24, 2015 at 5:52 PM, Benjamin Herrenschmidt
wrote:
> On Thu, 2015-06-25 at 02:08 +0200, Luis R. Rodriguez wrote:
>>
>> OK thanks I'll proceed with these patches then.
>>
>> > As for user mappings,
>>
>> Which APIs were you considering in this regard BTW?
>
> mmap of the generic /sys/bu
On Thu, 2015-06-25 at 02:08 +0200, Luis R. Rodriguez wrote:
>
> OK thanks I'll proceed with these patches then.
>
> > As for user mappings,
>
> Which APIs were you considering in this regard BTW?
mmap of the generic /sys/bus/pci/.../resource*
> > maybe the right thing to do is to let us do wha
On Thu, Jun 25, 2015 at 09:38:01AM +1000, Benjamin Herrenschmidt wrote:
> On Wed, 2015-06-24 at 15:29 -0700, Luis R. Rodriguez wrote:
>
> > Nope but at least what made me squint at this being a possible
> > "feature" was that in practice when reviewing all of the kernels
> > pending device drivers
On Wed, 2015-06-24 at 15:29 -0700, Luis R. Rodriguez wrote:
> Nope but at least what made me squint at this being a possible
> "feature" was that in practice when reviewing all of the kernels
> pending device drivers using MTRR (potential write-combine candidates)
> I encountered a slew of them wh
On Wed, Jun 24, 2015 at 3:05 PM, Benjamin Herrenschmidt
wrote:
> On Wed, 2015-06-24 at 18:38 +0200, Luis R. Rodriguez wrote:
>> On Wed, Jun 24, 2015 at 08:42:23AM +1000, Benjamin Herrenschmidt wrote:
>> > On Fri, 2015-06-19 at 15:08 -0700, Luis R. Rodriguez wrote:
>> > > From: "Luis R. Rodriguez"
On Wed, 2015-06-24 at 18:38 +0200, Luis R. Rodriguez wrote:
> On Wed, Jun 24, 2015 at 08:42:23AM +1000, Benjamin Herrenschmidt wrote:
> > On Fri, 2015-06-19 at 15:08 -0700, Luis R. Rodriguez wrote:
> > > From: "Luis R. Rodriguez"
> > >
> > > PCI BARs tell us whether prefetching is safe, but they
On Wed, Jun 24, 2015 at 08:42:23AM +1000, Benjamin Herrenschmidt wrote:
> On Fri, 2015-06-19 at 15:08 -0700, Luis R. Rodriguez wrote:
> > From: "Luis R. Rodriguez"
> >
> > PCI BARs tell us whether prefetching is safe, but they don't say anything
> > about write combining (WC). WC changes orderin
On Fri, 2015-06-19 at 15:08 -0700, Luis R. Rodriguez wrote:
> From: "Luis R. Rodriguez"
>
> PCI BARs tell us whether prefetching is safe, but they don't say anything
> about write combining (WC). WC changes ordering rules and allows writes to
> be collapsed, so it's not safe in general to use it
From: "Luis R. Rodriguez"
PCI BARs tell us whether prefetching is safe, but they don't say anything
about write combining (WC). WC changes ordering rules and allows writes to
be collapsed, so it's not safe in general to use it on a prefetchable
region.
Add pci_iomap_wc() and pci_iomap_wc_range(
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