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Re: FW: Db1500 PCI Auto Scan Question, bus master operation

To: Pete Popov <ppopov@mvista.com>, Tom Cernius <tcernius@correlant.com>
Subject: Re: FW: Db1500 PCI Auto Scan Question, bus master operation
From: fpga dsp <fpga_dsp@yahoo.com.au>
Date: Thu, 12 Jun 2003 12:15:17 +1000 (EST)
Cc: Linux MIPS mailing list <linux-mips@linux-mips.org>
In-reply-to: <1055373721.9976.690.camel@zeus.mvista.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
Sender: linux-mips-bounce@linux-mips.org
Hi,

I am using kernel 2.4.20-pre6 version on db1500 and
having problem with PCI card as bus master. Basicly,
the kernel can recognize the card and assign into
0x40000000 address region, irq is 1. Now that is
really strange, stty1 using irq 1 as well. Are they
the same or different. However ,the problem is that
after setup the device and trigger it, it should go
and fetch the descriptor and will fetch the content
pointed by that descriptor afterward but it only fetch
the descriptor and quiet. I am even try to trigger it
again by write into it register mapped on PCI memory
region but after the first trigger, the second trigger
doesn't appear on pci bus analyzer at all. 

Another issues, it when I look at au1000_eth.c device
driver , dma_alloc() function allocate a DMAable
buffer in KSEG0 region but pci_alloc_consistent return
in KSEG1 region. So which one is right?

Many thanks

 --- Pete Popov <ppopov@mvista.com> wrote: > On Wed,
2003-06-11 at 15:12, Tom Cernius wrote:
> > Hello,
> > 
> >    I am porting my first PCI driver for a PCI card
> hosted by the AMD Db1500
> > "Zinfandel" development board.
> >    This driver had been previously working on
> another host, where
> > CONFIG_PCI_AUTO was not enabled.
> > 
> >     My PCI card REQUIRES 0xFF000000 and 0x90000000
> be programmed into BAR0
> > and BAR1 respectively.
> >     My PCI card has nothing programmed into BAR0
> and BAR1 at power-up.
> >     My host Linux kernel was built with
> CONFIG_PCI, CONFIG_NEW_PCI, and
> > CONFIG_PCI_AUTO turned on in the .config file.
> 
> Why the 0xFF000000 and, in general, the hardcoded
> addresses?
> 
> Which kernel are you using?
> 
> >      I noticed that during boot, the kernel
> tickles my devices BAR's and
> > then writes these BARs with addresses in the range
> of
> >      4000 0000 thru 43FF FFFF
> 
> Right.
> 
> >      I have tried everything and although I am
> able to write the proper
> > (0xFF00 0000 and 0x9000 0000) addresses into the
> BAR's,
> >      I have been unable to successfully read
> anything from my PCI cards CPU
> > Register/Sdram space.
> 
> No, that's not going to work. I'll elaborate below.
> 
> >      I suspect that it is NOT possible to use
> hardcoded PCI BAR addresses
> > with the MIPS processor AND CONFIG_PCI_AUTO turned
> on,
> >      as the kernel expects (and configures the PCI
> BARS of) PCI devices to
> > reside in the address space 0x4000 0000 thru
> 0x43FF FFFF ??
> 
> Just to be clear, there's nothing MIPS generic about
> these addresses.
> They are Au1500 specific with a doze of arbitrary
> chose on my part. The
> addresses can be changed, carefully :)
> 
> >      I tried disabling the device, updating my
> BARS, reenabling in the
> > driver code (a loadable module).
> >      I tried writing the BARS just prior to
> tickling in the
> > linux/arch/mips/kernel/pci_auto.c code.
> >      I tried writing the BARS as soon as my
> device/vendor id are detected
> > also in the linux/arch/mips/kernel/pci_auto.c
> code.
> 
> OK, none of that will work the way you're doing it.
> Here's the problem:
> 
> The PCI space on the Au1500 SOC is addresses with
> 36bit physical
> addresses. The PCI noncachable memory space
> available for PCI devices is
> 0x4 0000 0000 to 0x5 0000 0000.  But, you can't
> write those addresses in
> a BAR and device drivers read the address and try to
> do an ioremap on
> it.  What I did was this:
> 
> - set pci memory start address to 0x4 4000 0000 
> - set pci memory end address to   0x4 43FF FFFF
> 
> These variables are in include/asm-mips/au1000.h. If
> you take a look at
> arch/mips/au1000/common/pci_ops.c, you'll see that
> in the
> pci_mem_resource structure these addresses are
> truncated to 32 bit:
> - 0x4000 0000 and 0x43FF FFFF. These are the
> addresses that the pci auto
> code sees and programs in the BARs. 
> 
> When a device driver reads the resource value,
> 0x4000 0000 for example,
> and calls ioremap on that address, the
> "fixup_bigphys_addr()" function
> will get called in __ioremap() in
> arch/mips/mm/ioremap.c. That function
> will detect that 0x4000 0000 falls within the pci
> memory window, and
> "fix it up" to the proper 36 bit physical address.
> In other words, it
> will return 0x4 4000 0000 so that 0x 4 4000 0000 can
> be remapped instead
> of 0x4000 0000 so you can access the pci memory
> window.  The actual
> physical pci address the SOC will put on the bus
> will be 0x4000 0000 and
> since that's what's programmed in the BAR, the
> device will respond to
> it.
> 
> The way you're approaching the problem is bypassing
> the entire
> "fixup_bigphys_addr()" (the function is in setup.c)
> mechanism and it has
> no chance or working.
> 
> In theory I think you should be able to do what you
> need. Suppose you
> bypassed pci_auto altogether, for example, and you
> hardcoded the BARs in
> setup.c.  One of your bars will be 0xFF000000 the
> other 0x90000000 (are
> both of these supposed to be pci memory addresses?).
> You need to fixup
> those addresses so that when ioremap is called with
> such an address, the
> 32 bit address will be fixed up to a 36 bit address
> and it's that
> address that will get remapped. For example, if a
> device driver calls
> ioremap with 0x9000 0000, you have to detect that
> address in the
> fixup_bigphys_addr() function, and return 0x4 9000
> 0000. Then when you
> use the returned virtual address to access the
> memory window, the CPU
> will understand this virtual address to translate to
> a PCI mem address
> and in turn it will put 0x9000 0000 on the bus. That
> should give you
> access to your device.
> 
> Pete
> 
> 
>  

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