So we have to focus on b53 and GPIO number it uses. By default b53 takes a GPIO number from the nvram looking for "gpioN=robo_reset". This is the first weird thing. In the output of "nvram show" you provided I can't see such nvram entry It means that

1. bcm47xx_nvram_gpio_pin should return -ENOENT

2. b53_switch_get_reset_gpio should return -ENOENT

3. dev->reset_gpio should be set to -ENOENT

4. b53_switch_reset_gpio should never touch gpio because of dev->reset_gpio being negative number

I've also checked default NVRAM generated by CFE (I found WRT300Nv11-cfe.bin) and it also doesn't contain "gpioN=robo_reset". Maybe there was such entry earlier (only in "nvram" partition), but you or DD-WRT cleared the nvram? Or maybe there is some bug in b53/bcm47xx I can't notice?

Anyway, according to the CFE logs this router uses (for real) GPIO 8 to reset switch:

Reset switch via GPIO 8 ...

For years OpenWrt was using GPIO 2 to reset switch on WRT300N V1.1 (see r18921). Hauke in his patch simply copied that to b53. It appears to be wrong. My guess is that GPIO 2 reboots device as well. It was never triggered by broadcom-diag, because it didn't try to reset switch for the second time.

P.S.
I've temporary removed "gpio7=robo_reset" from my device and b53 stopped touching GPIOs. So I think there had to be some wrong entry in your nvram before installing DD-WRT.

(Last edited by Zajec on 13 Apr 2014, 11:22)

@boblfoot: there is my final try. I'm not sure if you still have Hauke's patch applied or not, so I'll just describe how you should proceed.

Please open file target/linux/generic/files/drivers/net/phy/b53/b53_priv.h and replace first "b53_switch_get_reset_gpio" function with the following code:

static inline int b53_switch_get_reset_gpio(struct b53_device *dev)
{
    enum bcm47xx_board board = bcm47xx_board_get();

    switch (board) {
    case BCM47XX_BOARD_LINKSYS_WRT300NV11:
        pr_info("[%s] providing switch reset GPIO: %d\n", __FUNCTION__, 8);
        return 8;
    case BCM47XX_BOARD_LINKSYS_WRT310NV1:
        return 8;
    default:
        return bcm47xx_nvram_gpio_pin("robo_reset");
    }
}

Then recompile OpenWrt with tg3 enabled (you can use "Broadcom SoC, all Ethernet, No WiFi" for example).

@boblfoot: hey, did you have a moment to test code from my last post?

This should be fixed in https://dev.openwrt.org/changeset/41526