Re: brcmsmac: Data bus error in reading tsf_random

[Nathan Hintz <nlhintz@hotmail.com>]

Hauke Mehrtens <hauke@...> writes:

> 
> Hi Arend,
> 
> I am getting a Data bus error when brcmsmac tries to read tsf_random in
> brcms_c_wme_setparams. This does not happen when I add a printk
> somewhere near that read of tsf_random or when I replace the read with a
> constant. In b43 this code works, without this error for me, see
> b43_qos_params_upload(). With the BCM4716 I do not have this problem. It
> could be that this is caused by the broken PCIe controller in the BCM4716.
> 
> I am using brcmsmac from compat-wireless 2012-09-07, but I have also
> tried the most recent brcmsmac code from wireless-testing. brcmsmac uses
> the normal firmware from linux-firmware and I have also tried the new
> firmware posted some days ago with the same result.
> 
> I am using a BCM43224 connected to the PCIe controller of the BCM4716.
> 
> Are there any special requirements for reading tsf_random under mips?
> 
> To make my BCM43224 work I use this patch [0], the "printk("dummy\n");"
> is a hack to workaround the problem I am describing here.
> 
> Hauke
> 
> [0]:
>

<snip>

I encountered a similar DBE using the "broadcom-wl" driver (OpenWRT) on a 
Linksys E3000; except that it occurred when reading "ifs_ctl" (offset 0x688).  
I too tried putting in some printk's (in linux_osl.c), which caused the 
problem to go away.  I eventually found that doing a dummy read of 4 bytes 
at that particular address just prior to the actual two byte read caused 
the problem to go away as well (an ugly hack).  I can reproduce it if you 
want a stack trace.

Nathan