Re: [RFC][Patch] IBM Real-Time "SMI Free" mode driver -v4

Vernon Mauery
2010-09-24T20:46:33Z

On 24-Sep-2010 11:23 AM, Vernon Mauery wrote:
>On 24-Sep-2010 07:40 PM, Arnd Bergmann wrote:
>>On Friday 24 September 2010 19:09:43 Vernon Mauery wrote:
>>>I looked into this and tested it on some hardware, but it doesn't work.
>>>After more digging and poking, it looks like the reason is that the port
>>>IO address is not within the x86 standard port IO range.
>>>
>>>I tried something like this:
>>>
>>> addr = ioread32(&rtl_table->cmd_port_address);
>>> plen = rtl_cmd_width/8;
>>> if (rtl_cmd_type == RTL_ADDR_TYPE_MMIO)
>>> rtl_cmd_addr = ioremap(addr, plen);
>>> else
>>> rtl_cmd_addr = ioport_map(addr, plen);
>>> RTL_DEBUG("rtl_cmd_addr = %#llx\n", (u64)rtl_cmd_addr);
>>>
>>>It printed out that rtl_cmd_addr was 0, meaning the ioport_map failed.
>>>After more digging, it turns out that on at least one of the machines
>>>this code is targeted for, the port IO address (from the first line
>>>above) is 0x40000. Even if this did get mapped, the IO_COND macro would
>>>target it for MMIO access instead of PIO access. So I don't think I can
>>>use this method (even though it did make my code a lot nicer to read).
>>>
>>>Any suggestions?
>>
>>That seems really strange. I thought the inb/outb instructions could not
>>actually operate on addresses above 0x10000 at all, since they take a 16
>>bit address operand (DX register). Passing 0x40000 into inb should have the
>>same effect as zero AFAICT, which means that your existing code should not
>>work either.
>
>No, inb/outb have address as as unsigned long, which would explain
>why 0x40000 works with PIO. When doing inb/outb via the
>ioread/iowrite macros, the port value is the address (minus the
>offset) masked off to PIO_MASK, which is 16 bits on x86.
>
>So it looks like this really not going to work and I will have to go
>back to how it was before. Would it be tacky to write my own little
>macro?

Okay. I finally have it. In one of my changes, I inadvertently changed
the shape of the struct ibm_rtl_table, which is where I read the ioport
address from. This explains why the weird port. Once I fixed my table
so it was correct again, the port is 0x600, which is completely
reasonable and will work just fine with the iowrite functions. Thanks
for bringing this up -- it greatly simplifies things.

--Vernon