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    SubjectRe: [PATCH 3/3 v2] dmaengine: Add Freescale i.MX SDMA support
    Date
    Dne So 28. srpna 2010 17:18:17 Linus Walleij napsal(a):
    > 2010/8/23 Uwe Kleine-König <u.kleine-koenig@pengutronix.de>:
    > >> + evt = readl(SDMA_H_EVTOVR);
    > >> + mcu = readl(SDMA_H_HOSTOVR);
    > >> + dsp = readl(SDMA_H_DSPOVR);
    > >
    > > __raw_readl?
    >
    > Sorry I never understood this __raw_[read|write][b|w|l] vs.
    > plain read[b|w|l] proliferation in some drivers and code.
    >
    > What's the reason for?

    Hey,

    this trick is, if you create the VA<->PA mapping at the kernel start (eg. see
    how pxa_map_io() is replacedon some devices for instance), you then use the VA
    address you specified and use __raw_{read,write}[b,w,l](). So use
    __raw_{read,write}[b,w,l]() on drivers specific for certain device and use
    {read,write}[b,w,l]() on ioremap()ed memory areas, aka. in common drivers.

    Cheers

    >
    > Yours,
    > Linus Walleij
    >
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