linux-kernel - Re: [PATCH 1/5] dmaengine: add ep93xx DMA support

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Date:	Fri, 27 May 2011 00:58:19 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	H Hartley Sweeten <hartleys@...ionengravers.com>
Cc:	Mika Westerberg <mika.westerberg@....fi>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Vinod Koul <vinod.koul@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"ryan@...ewatersys.com" <ryan@...ewatersys.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	spi mailing list <spi-devel-general@...ts.sourceforge.net>
Subject: Re: [PATCH 1/5] dmaengine: add ep93xx DMA support

2011/5/26 H Hartley Sweeten <hartleys@...ionengravers.com>:

> I think the biggest hurdle with using the amba-pl022 driver is that the ep93xx
> spi peripheral does not have the registers with the pid and cid id's.  Without
> those I don't think the amba bus driver will be able to match the device to
> the driver.

This is not a problem. We have this code to dynamically create and
register a device with a specific periphid on ux500. It worked even
before my recent patches to amba's bus.c if you have only
zeroes in these registers:

struct amba_device *
dbx500_add_amba_device(const char *name, resource_size_t base,
                       int irq, void *pdata, unsigned int periphid)
{
        struct amba_device *dev;
        int ret;

        dev = kzalloc(sizeof *dev, GFP_KERNEL);
        if (!dev)
                return ERR_PTR(-ENOMEM);

        dev->dev.init_name = name;

        dev->res.start = base;
        dev->res.end = base + SZ_4K - 1;
        dev->res.flags = IORESOURCE_MEM;

        dev->dma_mask = DMA_BIT_MASK(32);
        dev->dev.coherent_dma_mask = DMA_BIT_MASK(32);

        dev->irq[0] = irq;
        dev->irq[1] = NO_IRQ;

        dev->periphid = periphid;

        dev->dev.platform_data = pdata;

        ret = amba_device_register(dev, &iomem_resource);
        if (ret) {
                kfree(dev);
                return ERR_PTR(ret);
        }

        return dev;
}

I'd recommend coming up with some clever numbering scheme
with invented vendor ID.

Yours,
Linus Walleij
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