Date: Tue, 16 Jun 2015 06:05:06 +0800
From: Herbert Xu <herbert@gondor.apana.org.au>
To: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-crypto@vger.kernel.org,
        Ruchika Gupta <ruchika.gupta@freescale.com>, kernel@pengutronix.de,
        Horia =?utf-8?Q?Geant=C4=83?= <horia.geanta@freescale.com>,
        Kim Phillips <kim.phillips@freescale.com>
Subject: Re: [BUG?] crypto: caam: little/big endianness on ARM vs PPC
Message-ID: <20150615220506.GA15134@gondor.apana.org.au>
References: <20150615155907.GC7947@pengutronix.de>
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On Mon, Jun 15, 2015 at 05:59:07PM +0200, Steffen Trumtrar wrote:
> Hi!
> 
> I'm working on CAAM support for the ARM-based i.MX6 SoCs. The current
> drivers/crypto/caam driver only works for PowerPC AFAIK.
> Actually, there isn't that much to do, to get support for the i.MX6 but
> one patch breaks the driver severely:
> 
> 	commit ef94b1d834aace7101de77c3a7c2631b9ae9c5f6
> 	crypto: caam - Add definition of rd/wr_reg64 for little endian platform
> 
> This patch adds
> 
> +#ifdef __LITTLE_ENDIAN
> +static inline void wr_reg64(u64 __iomem *reg, u64 data)
> +{
> +	wr_reg32((u32 __iomem *)reg + 1, (data & 0xffffffff00000000ull) >> 32);
> +	wr_reg32((u32 __iomem *)reg, data & 0x00000000ffffffffull);
> +}
> 
> The wr_reg64 function is only used in one place in the drivers/crypto/caam/jr.c
> driver: to write the dma_addr_t to the register. Without that patch everything
> works fine on ARM (little endian, 32bit), with that patch the driver will write
> 0's into the register that holds the DMA address (the numerically-higher) -> kernel hangs.
> Also, from my understanding, the comment above the defines, stating that you
> have to first write the numerically-lower and then the numerically-higher address
> on 32bit systems doesn't match with the implementation.
> 
> What I don't know/understand is if this makes any sense for any PowerPC implementation.
> 
> So, the question is, how to fix this? I'd prefer to do it directly in the jr driver
> instead of the ifdef-ery.
> 
> Something like
> 	if (sizeof(dma_addr_t) == sizeof(u32))
> 		wr_reg32(&jrp->rregs->inpring_base + 1, inpbusaddr);
> 	else if (sizeof(dma_addr_t) == sizeof(u64))
> 		wr_reg64(...)
> 
> or just go by DT compatible and then remove the inline function definitions.
> 
> As far as I can tell, the compatible wouldn't be needed for anything else in the
> jr driver, so maybe that is not optimal. On the other hand the sizeof(..)
> solution would only catch little endian on 32bit and not big endian (?!)
> I however don't know what combinations actually *have* to be caught, as I don't
> know, which exist.
> 
> So, what do you think people?

I'm adding a couple of CCs.

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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