linux-kernel - Re: [PATCH v6 07/12] usb: chipidea: add a usb2 driver for ci13xxx

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]

Message-ID: <20140926002339.GB3026@peterchendt>
Date:	Fri, 26 Sep 2014 08:23:40 +0800
From:	Peter Chen <peter.chen@...escale.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	<linux-arm-kernel@...ts.infradead.org>,
	Antoine Tenart <antoine.tenart@...e-electrons.com>,
	<thomas.petazzoni@...e-electrons.com>, <zmxu@...vell.com>,
	<devicetree@...r.kernel.org>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <balbi@...com>,
	<alexandre.belloni@...e-electrons.com>, <p.zabel@...gutronix.de>,
	<jszhang@...vell.com>, <sebastian.hesselbarth@...il.com>
Subject: Re: [PATCH v6 07/12] usb: chipidea: add a usb2 driver for ci13xxx

On Thu, Sep 25, 2014 at 09:11:35AM +0200, Arnd Bergmann wrote:
> On Thursday 25 September 2014 09:16:48 Peter Chen wrote:
> > > +     }
> > > +
> > > +     if (dev->of_node) {
> > > +             ret = ci_hdrc_usb2_dt_probe(dev, ci_pdata);
> > > +             if (ret)
> > > +                     goto clk_err;
> > > +     } else {
> > > +             ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
> > > +             if (ret)
> > > +                     goto clk_err;
> > > +     }
> > 
> > Hi Antoine, the above code may not be needed, since get phy and set dma
> > mask are common operation, we can do it at core code, the only thing you
> > need to do is something like: dev->dma_mask = DMA_BIT_MASK(32).
> > 
> 
> Certainly not, doing that would be broken for a number of reasons:
> 
> - dev->dma_mask is a pointer, a driver should not reassign that
> - the device may have been set up for a bus that requires a smaller mask
>   that is already set, changing the mask would cause data corruption
> - setting just the dma mask but not coherent mask is wrong
> - setting the dma mask can fail, e.g. if the mask is smaller than the
>   smallest memory zone, so you have to check the return value.
> 

In current chipidea structure, the parent (glue layer) driver will not be
used for dma, udc/host driver uses dma mask from child (core layer), at core
layer we will do:


	pdev->dev.dma_mask = dev->dma_mask; /* this device is parent */
	dma_set_coherent_mask(&pdev->dev, dev->coherent_dma_mask);

Would you suggestion us a suitable way? Or it is ok we use just Antoine's way that
call dma_coerce_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32)) at parent
driver no matter dt or non-dt? Thanks.

-- 
Best Regards,
Peter Chen
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/