linux-kernel - Re: [PATCH v6 12/14] crypto: caam - force DMA address to 32-bit on 64-bit i.MX SoCs

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Date:   Tue, 13 Aug 2019 13:38:04 +0000
From:   Horia Geanta <horia.geanta@....com>
To:     Andrey Smirnov <andrew.smirnov@...il.com>
CC:     "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        Chris Spencer <christopher.spencer@....co.uk>,
        Cory Tusar <cory.tusar@....aero>,
        Chris Healy <cphealy@...il.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        Aymen Sghaier <aymen.sghaier@....com>,
        Leonard Crestez <leonard.crestez@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 12/14] crypto: caam - force DMA address to 32-bit on
 64-bit i.MX SoCs

On 8/12/2019 10:27 PM, Andrey Smirnov wrote:
> On Mon, Aug 5, 2019 at 1:23 AM Horia Geanta <horia.geanta@....com> wrote:
>>
>> On 7/17/2019 6:25 PM, Andrey Smirnov wrote:
>>> @@ -603,11 +603,13 @@ static int caam_probe(struct platform_device *pdev)
>>>               ret = init_clocks(dev, ctrlpriv, imx_soc_match->data);
>>>               if (ret)
>>>                       return ret;
>>> +
>>> +             caam_ptr_sz = sizeof(u32);
>>> +     } else {
>>> +             caam_ptr_sz = sizeof(dma_addr_t);
>> caam_ptr_sz should be deduced by reading MCFGR[PS] bit, i.e. decoupled
>> from dma_addr_t.
>>
> 
> MCFGR[PS] is not mentioned in i.MX8MQ SRM and MCFG_PS in CTPR_MS is
> documented as set to "0" (seems to match in real HW as well). Doesn't
> seem like a workable solution for i.MX8MQ. Is there something I am
> missing?
> 
If CTPR_MS[PS]=0, this means CAAM does not allow choosing the "pointer size"
via MCFGR[PS]. Usually in this case the RM does not document MCFGR[PS] bit,
which is identical to MCFGR[PS]=0.

Thus the logic should be smth. like:
	caam_ptr_sz = CTPR_MS[PS] && MCFGR[PS] ? 64 : 32;

>> There is another configuration that should be considered
>> (even though highly unlikely):
>> caam_ptr_sz=1  - > 32-bit addresses for CAAM
>> CONFIG_ARCH_DMA_ADDR_T_64BIT=n - 32-bit dma_addr_t
>> so the logic has to be carefully evaluated.
>>
> 
> I don't understand what you mean here. 32-bit CAAM + 32-bit dma_addr_t
> should already be the case for i.MX6, etc. how is what you describe
> different?
> 
Sorry for not being clear.

caam_ptr_sz=1  - > 32-bit addresses for CAAM
should have been
caam_ptr_sz=*64*  - > 32-bit addresses for CAAM
i.e. CAAM address has "more than" (>) 32 bits (exact number of bits is
SoC / chassis specific) and thus will be represented on 8 bytes.

Thanks,
Horia