linux-kernel - Re: [PATCH] crypto: caam - do not reset pointer size if caam_ptr

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Message-ID: <VI1PR04MB44455C61E2D64EFF88CE39768C4A0@VI1PR04MB4445.eurprd04.prod.outlook.com>
Date:   Mon, 25 Nov 2019 12:02:38 +0000
From:   Iuliana Prodan <iuliana.prodan@....com>
To:     Horia Geanta <horia.geanta@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Aymen Sghaier <aymen.sghaier@....com>
CC:     "David S. Miller" <davem@...emloft.net>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        Andrey Smirnov <andrew.smirnov@...il.com>,
        Alison Wang <alison.wang@....com>
Subject: Re: [PATCH] crypto: caam - do not reset pointer size if caam_ptr_size
 is 64 bits

On 11/25/2019 9:49 AM, Horia Geanta wrote:
> On 11/25/2019 12:33 AM, Iuliana Prodan wrote:
>> In commit 'a1cf573ee95 ("crypto: caam - select DMA address
>> size at runtime")' CAAM pointer size (caam_ptr_size) is changed
>> from sizeof(dma_addr_t) to runtime value computed from MCFGR register.
>> At some point, the bit for Pointer Size should be reset to 0,
>> but only for the case when the CAAM pointer size if 32 bits.
>> Therefore, use caam_ptr_size instead of sizeof(dma_addr_t).
>>
> The logic is circular, see below.
> 
>> Fixes: a1cf573ee95 ("crypto: caam - select DMA address size at runtime")
> Please Cc the author(s) when adding Fixes tag.
> 
>> Cc: <stable@...r.kernel.org>
>> Signed-off-by: Iuliana Prodan <iuliana.prodan@....com>
>> ---
>>   drivers/crypto/caam/ctrl.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/crypto/caam/ctrl.c b/drivers/crypto/caam/ctrl.c
>> index d7c3c38..786eef6 100644
>> --- a/drivers/crypto/caam/ctrl.c
>> +++ b/drivers/crypto/caam/ctrl.c
>> @@ -674,7 +674,7 @@ static int caam_probe(struct platform_device *pdev)
>>   		clrsetbits_32(&ctrl->mcr, MCFGR_AWCACHE_MASK | MCFGR_LONG_PTR,
>>   			      MCFGR_AWCACHE_CACH | MCFGR_AWCACHE_BUFF |
>>   			      MCFGR_WDENABLE | MCFGR_LARGE_BURST |
>> -			      (sizeof(dma_addr_t) == sizeof(u64) ?
>> +			      (caam_ptr_sz == sizeof(u64) ?
>>   			       MCFGR_LONG_PTR : 0));
>>   
> Before this in caam_probe() there's:
> 	if (comp_params & CTPR_MS_PS && rd_reg32(&ctrl->mcr) & MCFGR_LONG_PTR)
> 		caam_ptr_sz = sizeof(u64);
> 	else
> 		caam_ptr_sz = sizeof(u32);
> 
> thus caam_ptr_sz is determined based on MCFGR:
> MCFGR[PS] ==> caam_ptr_sz
> so it no longer makes sense to reconfigure MCFGR based on caam_ptr_sz:
> caam_ptr_sz ==> MCFGR[PS]
> 
> The short-term fix would be to no longer touch MCFGR[PS], which is in line with
> commit a1cf573ee95 ("crypto: caam - select DMA address size at runtime")
> 
> Note however there's a small issue with the logic of kernel relying on
> MCFGR[PS] being previously configured (by U-boot etc.), see
> commit 39eaf759466f ("crypto: caam - fix pointer size for AArch64 boot loader, AArch32 kernel")
> 

So, what's your suggestion? We shouldn't reset the MCFGR[PS] at all? We 
should use the value set by u-boot?

Thanks,
Iulia

> In the long run, IMO the proper thing for the driver to do is to rely,
> whenever possible, on DT ("dma-ranges" property) / dma_mask provided by
> the device driver infrastructure, and not on MCFGR[PS]:
> [ DT "dma-ranges" ==> ] dma_mask ==> MCFGR[PS], caam_ptr_sz
> but that would probably involve too many changes for getting into -stable.
> 
> Horia
>