[OpenWrt-Devel] Rebooting boards with > 16M SPI flash
Arjen de Korte
arjen+openwrt at de-korte.org
Thu Jul 9 04:58:20 EDT 2015
Citeren Paul Fertser <fercerpav at gmail.com>:
> Arjen de Korte <arjen+openwrt at de-korte.org> writes:
>> Citeren Paul Fertser <fercerpav at gmail.com>:
>>> Another is
>>> that such a patch is mostly a bad substitute for proper hardware design.
>> Not really. There may not be a hardware reset line if the flash is
>> running in x4 data mode.
> Imagine there's a bug in the kernel that made it hang for real. Then
> you're counting on the watchdog (usually SoCs come with one integrated)
> to cleanly reboot the whole system. If the flash is used in QSPI or
> whatever other mode that doesn't allow a dedicated reset line then it
> needs to be powercycled on hardware level to ensure reliable operation,
> I think.
Exactly. If you're designing for rock bottom low cost (I'm a hardware
engineer), the SPI flash used will not have a dedicated reset line.
That is why helpdesks will always tell in case of problems to power
off a device for 30-60 seconds and then switch it back on again. In
many cases, a watchdog reset is not equivalent to a power on reset.
Best regards, Arjen
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