First results with netbook from John

[Gábor Stefanik]

One thing to try: swap the cards between the laptop and the netbook,
to check if the differences depend on the card or the system.

On Wed, May 5, 2010 at 8:03 PM, Larry Finger <Larry.Finger at lwfinger.net> wrote:
> I received the netbook from John last Saturday. It took a while to get
> it integrated into my network as this is my first Fedora system, but I
> now have some results to report.
>
> I loaded wl logging both MMIO and PCI configuration register reads and
> writes. The two types are now interleaved. The latter are logged with
> trace_printk() calls. Note: There is a bug in current kernel code that
> keeps these calls from being logged. Thanks to Stephen Rostedt for
> sorting out this problem.
>
> Both systems have the same core sequence and the same revisions. The
> cores in order are ChipCommon rev 0x16, IEEE 802.11 rev 0x0F, PCMCIA rev
> 0x0A, and PCI-E rev 0x09.
>
> I now know for certain that the netbook has an SPROM at offset 0x800.
> Trying to read at offset 0x1000, which is the SPROM location in the
> laptop, locks the machine, thus we need to determine the SPROM location
> without reading 0x1000.
>
> Fortunately, the wl driver reads and writes PCI configuration space from
> the Linux shim code, not from the binary blob, thus these operations can
> be traced.
>
> The _only_ differences between the laptop and netbook operations between
> startup and the reading of the SPROM are as follows:
>
> Register           Laptop           Netbook     Explanation
>
> PCI 0x0C             0x10            0x08       Cache Line Size
> PCI 0x04       0x00100106     0x001000006       Command Features [1]
> Core 0 0x2C          0x10            0x12       Chip Status Reg [2]
> Core 3 0x800       0x2801          0x3801       On laptop 0x3801 written
> Core 3 0x280a      0x6dbe          0xedbe       On laptop 0xedbe written
>
> The code then switches to Core 1 (802.11) and begins reading SPROM. On
> the laptop, it reads from 0x1000 and does a try at the smaller size
> SPROM, then switches to the larger size, just as ssb does. On the
> netbook, it immediately reads the larger size at offset 0x800.
>
> I have not yet looked closely at the differences between wl and ssb, but
> I did note one difference. In wl, bits 0xFF00 are cleared in PCI
> register 0x40. The only thing I could find is this code fragment from
> ipw2100 and ipw2200:
>
>   /* We disable the RETRY_TIMEOUT register (0x41) to keep
>    * PCI Tx retries from interfering with C3 CPU state */
>   pci_read_config_dword(pdev, 0x40, &val);
>   if ((val & 0x0000ff00) != 0)
>       pci_write_config_dword(pdev, 0x40, val & 0xffff00ff);
>
> Larry
>
> [1] The Wikipedia article on PCI configuration space says that this is a
> bitmask of features that can be enabled/disabled. I have no explanation
> of the details.
>
> [2] This extra bit looks most promising of all the differences. It is
> the bit involved in the is_sprom_available() routine for the 4315 device
> in the Broadcom driver that has been reverse engineered; however, the
> definition must have changed as that code would say there is no SPROM,
> which is clearly untrue.
>



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