Hi Kim, I contacted the Hardware folks and below is the statement from them : Unfortunately setting the DWT bit will also affect the operation of job descriptors, so I don't think that is a viable option. It looks like you will have to change the software to access all 32-bit registers as 32-bit quantities, even if two 32-bit registers appear to be two halves of a 64-bit register. If you do that it will work correctly on both big-endian and little-endian SoCs. Regards, Ruchika > -----Original Message----- > From: Kim Phillips [mailto:kim.phillips@xxxxxxxxxxxxx] > Sent: Thursday, May 08, 2014 5:25 AM > To: Gupta Ruchika-R66431 > Cc: linux-crypto@xxxxxxxxxxxxxxx; herbert@xxxxxxxxxxxxxxxxxxx > Subject: Re: [PATCH] crypto:caam - Modify width of few read only registers > > On Tue, 6 May 2014 23:09:15 -0500 > Gupta Ruchika-R66431 <ruchika.gupta@xxxxxxxxxxxxx> wrote: > > > Hi Kim, > > Hi Ruchika, > > > > From: Kim Phillips [mailto:kim.phillips@xxxxxxxxxxxxx] > > > Sent: Wednesday, May 07, 2014 2:02 AM > > > > > > On Tue, 6 May 2014 05:11:23 -0500 > > > Gupta Ruchika-R66431 <ruchika.gupta@xxxxxxxxxxxxx> wrote: > > > > > > > > From: Kim Phillips [mailto:kim.phillips@xxxxxxxxxxxxx] > > > > > Sent: Friday, May 02, 2014 2:15 AM > > > > > > > > > > On Tue, 29 Apr 2014 15:34:37 +0530 Ruchika Gupta > > > > > <ruchika.gupta@xxxxxxxxxxxxx> wrote: > > > > > > > > > > > Few read only registers like CHAVID, CTPR etc were wrongly > > > > > > defined as > > > > > > 64 bit registers. This functioned properly on the powerpc > platforms. > > > > > > However ARM SoC's wouldn't function correctly if these > > > > > > registers are defined as 64 bit. > > > > > > > > > > why wouldn't they function correctly? > > > > > > > > The SEC IP guide states these registers as 2 32 bit registers. So > > > > register definition in > > > > > > I'm looking at LS2100A's SEC reference manual, it clearly has the > > > CHAVID defined as one, single 64-bit register. What are you looking at? > > > > In the first version of guide they were defined as 64 bit. They were later > changed to 32 bit once issue was reported while testing on emulator. Latest > guide of LS2100 has them modified. A register width column has also been > added in the memory map now. > > I love how they try to cover up h/w bugs by amending the documentation... > > > > > crypto code should also have them defined as 32 bit registers. > > > > Defining > > > them as 64 bit in this case would be incorrect. > > > > > > > > Endianness of the CAAM IP varies with core's endiannes. In ARM > > > > SoC's , CAAM > > > block is also little endian. So in case the 2 - 32 bit registers > > > are treated as a 64 bit register, the result would be word swapped > > > as compared to powerpc platforms. As a result, the reads won't return the > right result. > > > > > > > > For eg. > > > > For the 2 32 bit registers CHAVID_MS(at address 0x0) and > > > > CHAVID_LS(address 0x4) , if core reads them as 64 bit word, > > > > > > > > In powerpc (big endian) platform - CHAVID_MS would be available in > > > > most significant portion of the 64 bit > > > word. > > > > CHAVID_LS would be the in least significant portion. > > > > This is as expected. > > > > > > > > In ARM (little endian) platform, 64 bit read would result in - > > > > CHAVID_MS in Least significant portion of the word and CHAVID_LS > > > > in the most significant location. > > > > This result is word swapped and the value read wouldn't be correct. > > > > > > hmm, have you looked at using the DWT "Double Word Transpose" bit in > > > the MCFGR? > > I am not able to locate this bit in MCFGR. > > It's bit 19: "Double Word Transpose. Setting this bit affects whether the > two words within a Dword are transposed when a double-word register is > accessed, ..." > > > However there are few swapping options present in Job ring configuration > and QICTL registers. Are you referring to these ? > > no. Plus, those don't sound relevant to accessing CHAVID... > > > Since these are 32 bit registers by nature, shouldn't we just treat them as > 32 bit instead of enabling the swapping option . > > depends on the definition of 'treat': I'd rather still use the superior 64- > bit accessors on all possible arches, if we can get them to work. > > Kim -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
