Re: [PATCH] mtx-1: add udelay to mtx1_pci_idsel

[Bruno Randolf <br1@einfach.org>]

On 07/24/2012 04:20 PM, Manuel Lauss wrote:
> On Tue, Jul 24, 2012 at 5:13 PM, Bruno Randolf <br1@einfach.org> wrote:
>> Hello? Any feedback?
>>
>> I know the description is not very good, but this patch is necessary for PCI
>> to work on the Surfbox.
>>
>> Thanks,
>> bruno
>>
>>
>> On 07/12/2012 09:54 PM, Bruno Randolf wrote:
>>>
>>> Without this udelay(1) PCI idsel does not work correctly on the
>>> "singleboard"
>>> (T-Mobile Surfbox) for the MiniPCI device. The result is that PCI
>>> configuration
>>> fails and the MiniPCI card is not detected correctly. Instead of
>>>
>>> PCI host bridge to bus 0000:00
>>> pci_bus 0000:00: root bus resource [mem 0x40000000-0x4fffffff]
>>> pci_bus 0000:00: root bus resource [io  0x1000-0xffff]
>>> pci 0000:00:03.0: BAR 0: assigned [mem 0x40000000-0x4000ffff]
>>> pci 0000:00:00.0: BAR 0: assigned [mem 0x40010000-0x40010fff]
>>> pci 0000:00:00.1: BAR 0: assigned [mem 0x40011000-0x40011fff]
>>>
>>> We see only the CardBus device:
>>>
>>> PCI host bridge to bus 0000:00
>>> pci_bus 0000:00: root bus resource [mem 0x40000000-0x4fffffff]
>>> pci_bus 0000:00: root bus resource [io  0x1000-0xffff]
>>> pci 0000:00:00.0: BAR 0: assigned [mem 0x40000000-0x40000fff]
>>> pci 0000:00:00.1: BAR 0: assigned [mem 0x40001000-0x40001fff]
>>>
>>> Later the device driver shows this error:
>>>
>>> ath5k 0000:00:03.0: cannot remap PCI memory region
>>> ath5k: probe of 0000:00:03.0 failed with error -5
>>>
>>> I assume that the logic chip which usually supresses the signal to the
>>> CardBus
>>> card has some settling time and without the delay it would still let the
>>> Cardbus interfere with the response from the MiniPCI card.
>>>
>>> What I cannot explain is why this behaviour shows up now and not in
>>> earlier
>>> kernel versions before. Maybe older PCI code was slower?
>>>
>>> Signed-off-by: Bruno Randolf <br1@einfach.org>
>>> ---
>>>    arch/mips/alchemy/board-mtx1.c |    2 ++
>>>    1 file changed, 2 insertions(+)
>>>
>>> diff --git a/arch/mips/alchemy/board-mtx1.c
>>> b/arch/mips/alchemy/board-mtx1.c
>>> index 295f1a9..e107a2f 100644
>>> --- a/arch/mips/alchemy/board-mtx1.c
>>> +++ b/arch/mips/alchemy/board-mtx1.c
>>> @@ -228,6 +228,8 @@ static int mtx1_pci_idsel(unsigned int devsel, int
>>> assert)
>>>           * adapter on the mtx-1 "singleboard" variant. It triggers a
>>> custom
>>>           * logic chip connected to EXT_IO3 (GPIO1) to suppress IDSEL
>>> signals.
>>>           */
>>> +       udelay(1);
>>> +
>>>          if (assert && devsel != 0)
>>>                  /* Suppress signal to Cardbus */
>>>                  alchemy_gpio_set_value(1, 0);   /* set EXT_IO3 OFF */
>>>
>
> Why don't you increase the delay value in the udelay() immediately following
> this part?

Yes that would be logical and was my first try. Unfortunately it does 
not work. It's weird, but the delay needs to be before as well.

bruno