| Message ID | 20200916071950.1493-2-gilad@benyossef.com |
|---|---|
| State | New |
| Headers | show |
| Series | [1/2] dt-bindings: crypto: update ccree optional params | expand |
On Thu, Oct 22, 2020 at 1:18 AM Gilad Ben-Yossef <gilad@benyossef.com> wrote: > > > Hi again, > > Any opinion on the suggested below? Sorry, lost in the pile... > Thanks! > Gilad > > > On Tue, Sep 29, 2020 at 9:08 PM Gilad Ben-Yossef <gilad@benyossef.com> wrote: >> >> >> On Wed, Sep 23, 2020 at 4:57 AM Rob Herring <robh@kernel.org> wrote: >> > >> > On Wed, Sep 16, 2020 at 10:19:49AM +0300, Gilad Ben-Yossef wrote: >> > > Document ccree driver supporting new optional parameters allowing to >> > > customize the DMA transactions cache parameters and ACE bus sharability >> > > properties. >> > > >> > > Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com> >> > > --- >> > > Documentation/devicetree/bindings/crypto/arm-cryptocell.txt | 4 ++++ >> > > 1 file changed, 4 insertions(+) >> > > >> > > diff --git a/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt b/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt >> > > index 6130e6eb4af8..1a1603e457a8 100644 >> > > --- a/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt >> > > +++ b/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt >> > > @@ -13,6 +13,10 @@ Required properties: >> > > Optional properties: >> > > - clocks: Reference to the crypto engine clock. >> > > - dma-coherent: Present if dma operations are coherent. >> > > +- awcache: Set write transactions cache attributes >> > > +- arcache: Set read transactions cache attributes >> > >> > dma-coherent already implies these are 011x, 101x or 111x. In my limited >> > experience configuring these (Calxeda SATA and ethernet), writeback, >> > write-allocate was pretty much always optimal. >> >> Indeed and these are the default. But not all SoC are born equal and >> we got a request to allow setting these. >> >> Maybe instead of numerical values have three possible verbal setting >> would be better? >> >> >> > > +- awdomain: Set write transactions ACE sharability domain (712, 703, 713 only) >> > > +- ardomain: Set read transactions ACE sharability domain (712, 703, 713 only) >> > >> > This probably needs something common. We may need something for Mali, >> > too. I don't think different settings for read and write makes much >> > sense nor does anything beyond IS or OS. >> >> I agree. Maybe >> >> sharability_domain: either "IS" or "OS"? It's still an Arm thing, so it would need at least an 'arm,' prefix. But ideally it wouldn't be Arm specific though I'm not sure if any such thing is needed for other arches. If common either for Arm or across arches, then it needs to be documented in a common doc with some wider agreement than what a device specific property needs. >> > These could also just be implied by the compatible string (and requiring >> > an SoC specific one). >> >> hm... we could do it but this will require us to know (and publicly >> acknowledge) of every SoC making use of this piece of hardware design. That's already a requirement in general. Sometimes we can avoid it, but that's cases of getting lucky. >> There is currently no other part of the driver that needs this. If your DT is part of firmware, then waiting until adding some driver feature or quirk based on a new DT property is too late. Whereas with a SoC specific compatible, you can handle any new feature or quirk without a DT change (e.g. just a stable kernel update). Some platforms may not care about that model, but in general that's the policy we follow. Not doing that, we end up with the DWC3 binding. A fallback compatible is how we avoid updating drivers for every single SoC unless needed. Rob
On Mon, Nov 16, 2020 at 8:54 PM Rob Herring <robh@kernel.org> wrote: > > On Thu, Oct 22, 2020 at 1:18 AM Gilad Ben-Yossef <gilad@benyossef.com> wrote: > > > > > > Hi again, > > > > Any opinion on the suggested below? > > Sorry, lost in the pile... No problem at all. I know how it is... > > > > > > On Tue, Sep 29, 2020 at 9:08 PM Gilad Ben-Yossef <gilad@benyossef.com> wrote: > >> > >> > >> On Wed, Sep 23, 2020 at 4:57 AM Rob Herring <robh@kernel.org> wrote: > >> > > >> > On Wed, Sep 16, 2020 at 10:19:49AM +0300, Gilad Ben-Yossef wrote: > >> > > Document ccree driver supporting new optional parameters allowing to > >> > > customize the DMA transactions cache parameters and ACE bus sharability > >> > > properties. > >> > > > >> > > Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com> > >> > > --- > >> > > Documentation/devicetree/bindings/crypto/arm-cryptocell.txt | 4 ++++ > >> > > 1 file changed, 4 insertions(+) > >> > > > >> > > diff --git a/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt b/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt > >> > > index 6130e6eb4af8..1a1603e457a8 100644 > >> > > --- a/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt > >> > > +++ b/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt > >> > > @@ -13,6 +13,10 @@ Required properties: > >> > > Optional properties: > >> > > - clocks: Reference to the crypto engine clock. > >> > > - dma-coherent: Present if dma operations are coherent. > >> > > +- awcache: Set write transactions cache attributes > >> > > +- arcache: Set read transactions cache attributes > >> > <snip> > >> > These could also just be implied by the compatible string (and requiring > >> > an SoC specific one). > >> > >> hm... we could do it but this will require us to know (and publicly > >> acknowledge) of every SoC making use of this piece of hardware design. > > That's already a requirement in general. Sometimes we can avoid it, > but that's cases of getting lucky. > > >> There is currently no other part of the driver that needs this. > > If your DT is part of firmware, then waiting until adding some driver > feature or quirk based on a new DT property is too late. Whereas with > a SoC specific compatible, you can handle any new feature or quirk > without a DT change (e.g. just a stable kernel update). Some platforms > may not care about that model, but in general that's the policy we > follow. Not doing that, we end up with the DWC3 binding. > > A fallback compatible is how we avoid updating drivers for every > single SoC unless needed. OK, I now better understand what you meant and that does make some sense and I will defer to your better judgment about the proper way to do this. Having said that, there is still something that bugs me about this, even just at the level of better understanding why we do things: Way back when, before DT, we had SoC specific code that identified the SoC somehow and set things up in a SoC specific way. Then we introduced DT as a way to say - "hey look, this is how my busses looks like, these are the devices I have, deal with it" and I always assumed that this was meant as a way to release us from having SoC specific setup code. It seems now potentially every SoC vendor needs to modify not just the device tree source (which makes sense of course) but also the driver supporting their platform. It now looks like we've come a full circle to me :-) Thanks! Gilad
On 2020-11-16 18:54, Rob Herring wrote: > On Thu, Oct 22, 2020 at 1:18 AM Gilad Ben-Yossef <gilad@benyossef.com> wrote: >> >> >> Hi again, >> >> Any opinion on the suggested below? > > Sorry, lost in the pile... > >> Thanks! >> Gilad >> >> >> On Tue, Sep 29, 2020 at 9:08 PM Gilad Ben-Yossef <gilad@benyossef.com> wrote: >>> >>> >>> On Wed, Sep 23, 2020 at 4:57 AM Rob Herring <robh@kernel.org> wrote: >>>> >>>> On Wed, Sep 16, 2020 at 10:19:49AM +0300, Gilad Ben-Yossef wrote: >>>>> Document ccree driver supporting new optional parameters allowing to >>>>> customize the DMA transactions cache parameters and ACE bus sharability >>>>> properties. >>>>> >>>>> Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com> >>>>> --- >>>>> Documentation/devicetree/bindings/crypto/arm-cryptocell.txt | 4 ++++ >>>>> 1 file changed, 4 insertions(+) >>>>> >>>>> diff --git a/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt b/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt >>>>> index 6130e6eb4af8..1a1603e457a8 100644 >>>>> --- a/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt >>>>> +++ b/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt >>>>> @@ -13,6 +13,10 @@ Required properties: >>>>> Optional properties: >>>>> - clocks: Reference to the crypto engine clock. >>>>> - dma-coherent: Present if dma operations are coherent. >>>>> +- awcache: Set write transactions cache attributes >>>>> +- arcache: Set read transactions cache attributes >>>> >>>> dma-coherent already implies these are 011x, 101x or 111x. In my limited >>>> experience configuring these (Calxeda SATA and ethernet), writeback, >>>> write-allocate was pretty much always optimal. >>> >>> Indeed and these are the default. But not all SoC are born equal and >>> we got a request to allow setting these. >>> >>> Maybe instead of numerical values have three possible verbal setting >>> would be better? >>> >>> >>>>> +- awdomain: Set write transactions ACE sharability domain (712, 703, 713 only) >>>>> +- ardomain: Set read transactions ACE sharability domain (712, 703, 713 only) >>>> >>>> This probably needs something common. We may need something for Mali, >>>> too. I don't think different settings for read and write makes much >>>> sense nor does anything beyond IS or OS. >>> >>> I agree. Maybe >>> >>> sharability_domain: either "IS" or "OS"? > > It's still an Arm thing, so it would need at least an 'arm,' prefix. > But ideally it wouldn't be Arm specific though I'm not sure if any > such thing is needed for other arches. If common either for Arm or > across arches, then it needs to be documented in a common doc with > some wider agreement than what a device specific property needs. "dma-coherent" already encapsulates the shareability. To claim coherency you need to be able to access memory with inner shareable inner-outer write back attributes, because that's how regular kernel memory is mapped. If you don't claim coherency, then you should be using non-cacheable (and thus implicitly outer shareable) attributes, because there may still be cacheable aliases hanging around and if you inadvertently snoop those instead of going direct to DRAM as everything else expects, you're going to have a bad time. Essentially, Linux only uses two sets of memory attributes for DMA memory, so any perceived need for more than that is already something sufficiently esoteric that it probably doesn't need a generic binding. I'm aware that it's against type for me to be arguing Linux details in a DT binding, but I checked the TRMs for some of these devices and they essentially say "you don't program the hardware directly, you use the Linux driver we give you", so it seems like this binding is specifically intended never to be consumed by anything else. >>>> These could also just be implied by the compatible string (and requiring >>>> an SoC specific one). >>> >>> hm... we could do it but this will require us to know (and publicly >>> acknowledge) of every SoC making use of this piece of hardware design. > > That's already a requirement in general. Sometimes we can avoid it, > but that's cases of getting lucky. > >>> There is currently no other part of the driver that needs this. > > If your DT is part of firmware, then waiting until adding some driver > feature or quirk based on a new DT property is too late. Whereas with > a SoC specific compatible, you can handle any new feature or quirk > without a DT change (e.g. just a stable kernel update). Some platforms > may not care about that model, but in general that's the policy we > follow. Not doing that, we end up with the DWC3 binding. > > A fallback compatible is how we avoid updating drivers for every > single SoC unless needed. IMO if this is like PL330 where you just stick some raw AXI attributes in a register and that's what goes out on transactions then it's not really part of the platform description anyway, it's just driver policy. If folks want to tweak the driver's behaviour for secret SoC-specific performance optimisation, then give them some module parameters or a sysfs interface. I'm assuming this has to be purely a performance thing, because I can't see how two different integrations could reasonably depend on different baseline attributes for correctness, and even if they did then you'd be able to determine that from the compatible strings, because they would be different, because those integrations would be fundamentally *not* compatible with each other. Robin.
On Tue, Nov 17, 2020 at 1:39 AM Gilad Ben-Yossef <gilad@benyossef.com> wrote: > > On Mon, Nov 16, 2020 at 8:54 PM Rob Herring <robh@kernel.org> wrote: > > > > On Thu, Oct 22, 2020 at 1:18 AM Gilad Ben-Yossef <gilad@benyossef.com> wrote: > > > > > > > > > Hi again, > > > > > > Any opinion on the suggested below? > > > > Sorry, lost in the pile... > > No problem at all. I know how it is... > > > > > > > > > > > On Tue, Sep 29, 2020 at 9:08 PM Gilad Ben-Yossef <gilad@benyossef.com> wrote: > > >> > > >> > > >> On Wed, Sep 23, 2020 at 4:57 AM Rob Herring <robh@kernel.org> wrote: > > >> > > > >> > On Wed, Sep 16, 2020 at 10:19:49AM +0300, Gilad Ben-Yossef wrote: > > >> > > Document ccree driver supporting new optional parameters allowing to > > >> > > customize the DMA transactions cache parameters and ACE bus sharability > > >> > > properties. > > >> > > > > >> > > Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com> > > >> > > --- > > >> > > Documentation/devicetree/bindings/crypto/arm-cryptocell.txt | 4 ++++ > > >> > > 1 file changed, 4 insertions(+) > > >> > > > > >> > > diff --git a/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt b/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt > > >> > > index 6130e6eb4af8..1a1603e457a8 100644 > > >> > > --- a/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt > > >> > > +++ b/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt > > >> > > @@ -13,6 +13,10 @@ Required properties: > > >> > > Optional properties: > > >> > > - clocks: Reference to the crypto engine clock. > > >> > > - dma-coherent: Present if dma operations are coherent. > > >> > > +- awcache: Set write transactions cache attributes > > >> > > +- arcache: Set read transactions cache attributes > > >> > > > <snip> > > > >> > These could also just be implied by the compatible string (and requiring > > >> > an SoC specific one). > > >> > > >> hm... we could do it but this will require us to know (and publicly > > >> acknowledge) of every SoC making use of this piece of hardware design. > > > > That's already a requirement in general. Sometimes we can avoid it, > > but that's cases of getting lucky. > > > > >> There is currently no other part of the driver that needs this. > > > > If your DT is part of firmware, then waiting until adding some driver > > feature or quirk based on a new DT property is too late. Whereas with > > a SoC specific compatible, you can handle any new feature or quirk > > without a DT change (e.g. just a stable kernel update). Some platforms > > may not care about that model, but in general that's the policy we > > follow. Not doing that, we end up with the DWC3 binding. > > > > A fallback compatible is how we avoid updating drivers for every > > single SoC unless needed. > > OK, I now better understand what you meant and that does make some > sense and I will defer to your better judgment about the proper way > to do this. > > Having said that, there is still something that bugs me about this, > even just at the level of better understanding why we do things: > > Way back when, before DT, we had SoC specific code that identified the > SoC somehow and set things up in a SoC specific way. > Then we introduced DT as a way to say - "hey look, this is how my > busses looks like, these are the devices I have, deal with it" and I > always assumed that this was meant as a way to release us from having > SoC specific setup code. Yes, but in the end it's a judgement call as to what the boundary is. Take clocks for example, in the beginning we were trying to describe clocks on a mux/divider/gate level in DT. We realized this would result in hundreds to thousands of DT nodes and it would never be completely correct. So we model only the leaf clocks for the most part and there's lots of SoC code for clock controller blocks still. The questions for having properties or not to ask is: Is this board specific? Yes, then use a property. Who needs to change this and when? Should/would you want to control this in your PC BIOS or via a BIOS update? Zero SoC code was never a goal. It was about a standard way to define SoCs and having common frameworks (we have a common clock api, but not implementation at the time). We have *way* less SoC code per SoC than we used to. At the start of the DT conversion for Arm, we had ~400 boards and now we're at ~1400 last I checked. > It seems now potentially every SoC vendor needs to modify not just the > device tree source (which makes sense of course) but also the driver > supporting their platform. > It now looks like we've come a full circle to me :-) As I said, if the h/w is 'exactly the same' (hint: it rarely is), then use a fallback compatible. Then the new SoC specific compatible is there just in case. Think of compatible just as a VID/PID in PCI and USB land (though the closest thing to a fallback there is class codes). They are the only way we can uniquely identify h/w. Rob
Hi, On Tue, Nov 17, 2020 at 4:07 PM Robin Murphy <robin.murphy@arm.com> wrote: > > On 2020-11-16 18:54, Rob Herring wrote: > > On Thu, Oct 22, 2020 at 1:18 AM Gilad Ben-Yossef <gilad@benyossef.com> wrote: > >> ... > > IMO if this is like PL330 where you just stick some raw AXI attributes > in a register and that's what goes out on transactions then it's not > really part of the platform description anyway, it's just driver policy. > If folks want to tweak the driver's behaviour for secret SoC-specific > performance optimisation, then give them some module parameters or a > sysfs interface. I'm assuming this has to be purely a performance thing, > because I can't see how two different integrations could reasonably > depend on different baseline attributes for correctness, and even if > they did then you'd be able to determine that from the compatible > strings, because they would be different, because those integrations > would be fundamentally *not* compatible with each other. > So, I checked internally where we get this requirement and it seems you are right. I'm dropping the Dt bindings and in fact the ability to customize those attributes beyond the basic coherent/non coherent configuration which we already support and will just update the setting to what we think is best. Thanks for clearing this up. Gilad -- Gilad Ben-Yossef Chief Coffee Drinker values of β will give rise to dom!
diff --git a/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt b/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt index 6130e6eb4af8..1a1603e457a8 100644 --- a/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt +++ b/Documentation/devicetree/bindings/crypto/arm-cryptocell.txt @@ -13,6 +13,10 @@ Required properties: Optional properties: - clocks: Reference to the crypto engine clock. - dma-coherent: Present if dma operations are coherent. +- awcache: Set write transactions cache attributes +- arcache: Set read transactions cache attributes +- awdomain: Set write transactions ACE sharability domain (712, 703, 713 only) +- ardomain: Set read transactions ACE sharability domain (712, 703, 713 only) Examples:
Document ccree driver supporting new optional parameters allowing to customize the DMA transactions cache parameters and ACE bus sharability properties. Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com> --- Documentation/devicetree/bindings/crypto/arm-cryptocell.txt | 4 ++++ 1 file changed, 4 insertions(+)