linux-kernel - Re: [PATCH v1 1/4] dmaengine: imx-sdma: add memcpy interface

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 11 Jul 2018 09:08:56 +0200
From:   Sascha Hauer <s.hauer@...gutronix.de>
To:     Robin Gong <yibin.gong@....com>
Cc:     "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "vkoul@...nel.org" <vkoul@...nel.org>,
        dl-linux-imx <linux-imx@....com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        Fabio Estevam <fabio.estevam@....com>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v1 1/4] dmaengine: imx-sdma: add memcpy interface

On Wed, Jul 11, 2018 at 07:05:23AM +0000, Robin Gong wrote:
> 
> 
> > -----Original Message-----
> > From: Sascha Hauer [mailto:s.hauer@...gutronix.de]
> > Sent: 2018年7月11日 15:01
> > To: Robin Gong <yibin.gong@....com>
> > Cc: vkoul@...nel.org; dan.j.williams@...el.com; shawnguo@...nel.org; Fabio
> > Estevam <fabio.estevam@....com>; linux@...linux.org.uk;
> > linux-arm-kernel@...ts.infradead.org; kernel@...gutronix.de;
> > dmaengine@...r.kernel.org; linux-kernel@...r.kernel.org; dl-linux-imx
> > <linux-imx@....com>
> > Subject: Re: [PATCH v1 1/4] dmaengine: imx-sdma: add memcpy interface
> > 
> > On Wed, Jul 11, 2018 at 06:56:18AM +0000, Robin Gong wrote:
> > >
> > > > -----Original Message-----
> > > > From: Sascha Hauer [mailto:s.hauer@...gutronix.de]
> > > > Sent: 2018年7月11日 14:25
> > > > To: Robin Gong <yibin.gong@....com>
> > > > Cc: vkoul@...nel.org; dan.j.williams@...el.com; shawnguo@...nel.org;
> > > > Fabio Estevam <fabio.estevam@....com>; linux@...linux.org.uk;
> > > > linux-arm-kernel@...ts.infradead.org; kernel@...gutronix.de;
> > > > dmaengine@...r.kernel.org; linux-kernel@...r.kernel.org;
> > > > dl-linux-imx <linux-imx@....com>
> > > > Subject: Re: [PATCH v1 1/4] dmaengine: imx-sdma: add memcpy
> > > > interface
> > > >
> > > > On Wed, Jul 11, 2018 at 12:23:10AM +0800, Robin Gong wrote:
> > > > > Add MEMCPY support, meanwhile, add SDMA_BD_MAX_CNT instead of
> > > > > '0xffff'.
> > > > >
> > > > > Signed-off-by: Robin Gong <yibin.gong@....com>
> > > > > ---
> > > > > +static struct dma_async_tx_descriptor *sdma_prep_memcpy(
> > > > > +		struct dma_chan *chan, dma_addr_t dma_dst,
> > > > > +		dma_addr_t dma_src, size_t len, unsigned long flags) {
> > > > > +	struct sdma_channel *sdmac = to_sdma_chan(chan);
> > > > > +	struct sdma_engine *sdma = sdmac->sdma;
> > > > > +	int channel = sdmac->channel;
> > > > > +	size_t count;
> > > > > +	int i = 0, param;
> > > > > +	struct sdma_buffer_descriptor *bd;
> > > > > +	struct sdma_desc *desc;
> > > > > +
> > > > > +	if (!chan || !len)
> > > > > +		return NULL;
> > > > > +
> > > > > +	dev_dbg(sdma->dev, "memcpy: %pad->%pad, len=%zu,
> > channel=%d.\n",
> > > > > +		&dma_src, &dma_dst, len, channel);
> > > > > +
> > > > > +	desc = sdma_transfer_init(sdmac, DMA_MEM_TO_MEM, len /
> > > > SDMA_BD_MAX_CNT
> > > > > +					+ 1);
> > > > > +	if (!desc)
> > > > > +		goto err_out;
> > > > > +
> > > > > +	do {
> > > > > +		count = min_t(size_t, len, SDMA_BD_MAX_CNT);
> > > >
> > > > When len is bigger than 0xffff you initialize count to 0xffff...
> > > In this case, the data will be split into several bds, for example, If
> > > the total count is 0x10000, two bd used then. One is for 0xffff,
> > > Another is for the last 1
> > 
> > And you are doing byte size DMA? Wouldn't word size accesses be more
> > optimal?
> > 
> > Sascha
> Default is words, and I'll force the buswidth to word and set into BD.
> sdma->dma_device.copy_align = DMAENGINE_ALIGN_4_BYTES;

So guess which alignment the second transfer has when the first has the
size 0xffff.

Sascha

-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |