linux-kernel - Re: [PATCH v18 6/7] crypto: caam: cleanup CONFIG

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Date:   Wed, 4 Jul 2018 15:59:01 +0000
From:   Horia Geanta <horia.geanta@....com>
To:     Fabio Estevam <festevam@...il.com>
CC:     Logan Gunthorpe <logang@...tatee.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Aymen Sghaier <aymen.sghaier@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Linux-Arch <linux-arch@...r.kernel.org>,
        "linux-ntb@...glegroups.com" <linux-ntb@...glegroups.com>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dan Douglass <dan.douglass@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH v18 6/7] crypto: caam: cleanup CONFIG_64BIT ifdefs when
 using io{read|write}64

On 7/4/2018 6:06 PM, Fabio Estevam wrote:
> Hi Horia,
> 
> On Wed, Jul 4, 2018 at 8:45 AM, Horia Geanta <horia.geanta@....com> wrote:
> 
>> I think there are two separate issues here:
>>
>> 1. Semantics of operations in io-64-nonatomic-lo-hi.h, io-64-nonatomic-hi-lo.h
>>
>> Logan, you mentioned the following (which unfortunately I somehow missed):
>> https://lore.kernel.org/lkml/c3f2e061-5ed1-5c74-b955-3d2bfb0da074@deltatee.com
>> The lo_hi/hi_lo functions seem to always refer to the data being written
>> or read not to the address operated on.
>>
>> OTOH, initial commit that added asm-generic/io-64-nonatomic-lo-hi.h and
>> asm-generic/io-64-nonatomic-hi-lo.h mentions:
>> 797a796a13df6 ("asm-generic: architecture independent readq/writeq for 32bit
>> environment")
>> - <asm-generic/io-64-nonatomic-lo-hi.h> provides non-atomic readq/ writeq with
>> the order of lower address -> higher address
>> - <asm-generic/io-64-nonatomic-hi-lo.h> provides non-atomic readq/ writeq with
>> reversed order
>>
>> I think we should keep the initial semantics when adding support for
>> io{read|write}64, i.e. "lo" and "hi" to refer to address and not to value.
>>
>> Actually this is the semantics intended for the CAAM patch, see the note at the
>> end of the commit message that refers to addresses, not values:
>> To be consistent with CAAM engine HW spec: in case of 64-bit registers,
>> irrespective of device endianness, the lower address should be read from
>> / written to first, followed by the upper address.
>>
>>
>> 2. CAAM driver I/O accessors for i.MX case
>>
>> CAAM block in some i.MX parts has broken endianness for 64b registers.
>> For e.g. for i.MX6S/SL/D/Q even though CAAM is little endian, BARs for I/O rings
>> have to be programmed as:
>> I/O Ring BAR+0: unused
>> I/O Ring BAR+4: IOVA (32-bit little endian)
>> when the proper layout (for a 64b register) would have been to program IOVA at
>> BAR+0.
>>
>> This explains why I/O accessors in CAAM driver handle things differently in case
>> caam_imx=true.
>>
>> Since this quirk cannot be accommodated in generic fashion, code dealing with
>> caam_imx has to stay.
> 
> Should I sent a revert of patch 46e4bf08f6388 for the boot regression for now?
> 
> Then the two issues you pointed out could be fixed later.
> 
I guess it would be better this way.

Thanks,
Horia