Re: [PATCH #upstream] sata_nv: use hardreset only for post-boot probing

[Jeff Garzik <jeff@garzik.org>]

Tejun Heo wrote:
> When I thought it was finally defeated, it came back with vengeance.
> The failure cases are ever more convoluted.  Now there is a single
> combination which fails boot probing - MCP5x + Intel SSD and there are
> two hotplug failure reports on different flavors where softreset fails
> to bring up the device.
> 
> Through the many bug reports after the switch to hardreset, the
> following patterns emerged.
> 
> - Softreset during boot always works.
> 
> - Hardreset during boot sometimes fails to bring up the link on
>   certain comibnations and device signature acquisition is unreliable.
> 
> - Hardreset is often necessary after hotplug.
> 
> It looks like the old behavior of preferring softreset was somehow
> pretty close to the working reset protocol although it could have lost
> a device during phy error handling by issuing hardreset.
> 
> This patch implements nv_hardreset() which kicks in only for post-boot
> (!LOADING) device probing resets.  This should be able to work around
> all known problem cases.  This isn't perfect but given the various
> hardreset quirks on these controllers, I think this is as good as it
> can get.
> 
> Tested on mcp5x (swncq), nf3 and ck804 for all both boot, warm and
> hot probing cases.
> 
> Kudos to all the bug reporters and their painful hours with these damn
> controllers.  ;-)
> 
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Cc: Robert Hancock <hancockr@shaw.ca>
> Reported-by: David Lang <david@lang.hm>
> Reported-by: Samo Vodopivec <lament.email.si@gmail.com>
> ---
> Jeff, please queue for 2.6.31.  I think this should be pretty safe but
> well I've said that before several times for sata_nv already and was
> wrong, so...
> 
> Thanks.
> 
>  drivers/ata/sata_nv.c |  131 ++++++++++++++++++++++++++++++--------------------
>  1 file changed, 81 insertions(+), 50 deletions(-)

applied