linux-kernel - Re: PCIE

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Date:	Thu, 24 May 2007 04:07:31 +0400
From:	Manu Abraham <abraham.manu@...il.com>
To:	Roland Dreier <rdreier@...co.com>
CC:	Greg KH <greg@...ah.com>, linux-pci@...ey.karlin.mff.cuni.cz,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: PCIE

Roland Dreier wrote:
>  > It looks so, from the logs. The only problem is i can't disable the
>  > interrupts, if i write "0" to 0x500, the interrupt/enable register, it
>  > gives me a solid freeze. If i read from the handler, commenting out the
>  > disable interrupts in init, that read also gives me a solid freeze. This
>  > lead me to think that there could be some problem with the MMIO block
>  > access.
> 
> OK, this looks reasonable:
> 
>  > #define saa716x_write(dat, addr)	writel((dat), (saa716x->mmio)+(addr))
> 
> although
> 
>   a) your driver has no hope of working on a system with more than one
>      device of this type; and

to make it working with more than one device shouldn't be hard once it
is going on.

>   b) there's really no point in obfuscating a simple use of writel()
>      this way.
> 
> Why does the device come up in a state where it generates a stream of
> interrupts as soon as you enable the PCI device?  That's somewhat
> unusual behavior, although certainly not unheard of.

Will ask the vendor, what's going on.

> This really has the feel of a typical driver bug to me, not anything
> related to general PCIe access.  I've definitely wedged my system many
> times while trying to poke a device the right way.

Yeah, you seem to sound right.

> Also, where are you getting the offset of 0x500 from?  

The register offset is according to the device specs. Of course i
already found some wrong offsets etc, maybe this one's wrong too, probably.

> Is it possible
> that the offset is really being given to you in bits (so you should
> use 0x500 / 8) or 32-bit words (so you should use an offset of 0x500 *

It says, the base address is currently 500h

> 4)?  Are the datasheet / programming docs available for this device?

Working with this device, under NDA with the vendor.

> I actually have:
> 
>   02:00.0 Multimedia controller: Philips Semiconductors Unknown device 7162
> 
> in one of my systems so I'd be somewhat interested in getting a driver
> working too.

Cool, won't be that long, just the bridge part remains, most other parts
are done or do exist.

Thanks,
Manu

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