[U-Boot] [IXP42x PATCH series v4 13/17] add dvlhost (dLAN 200 AV Wireless G) board

[Michael Schwingen]

Am 05/21/2011 02:06 AM, schrieb Marek Vasut:
>
>> +	/* Setup GPIO's for 33MHz clock output */
>> +	GPIO_OUTPUT_ENABLE(CONFIG_SYS_GPIO_PCI_CLK);
>> +	GPIO_OUTPUT_ENABLE(CONFIG_SYS_GPIO_EXTBUS_CLK);
>> +	writel(0x01FF01FF, IXP425_GPIO_GPCLKR);
>> +
>> +	/* turn off all LEDs */
>> +	writew(0x0000, DVLHOST_LED_LATCH);
>> +
>> +	udelay(533);
> Why 533 ?
>
>> +	GPIO_OUTPUT_SET(CONFIG_SYS_GPIO_PCIRST);

Hm - that is copied from the PCI init sequence in pci_ixp.c - however,
the constant *does* look dodgy:
We need at least 100us reset pulse *after the clock is stable* -
whatever time that requires.
On the other hand, the PCI spec requires 2^25 clocks after reset before
the first configuration access, which would be around 1s - we probably
violate that, since the timing depends on what other code delays
operation until the first PCI configuration access.

Since PCI is not 100% functional (at least in my attempts), even on the
existing IXDP425 board, I would like to leave this as is for now - at
least it is consistent across all IXP boards.

cu
Michael