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

[Bruno Randolf <br1@einfach.org>]

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 */
>