Re: [PATCH v2] ata: libata-pmp: add JMicron JMS562 quirk

[Niklas Cassel <cassel@kernel.org>]

On Wed, Jun 10, 2026 at 05:09:34PM +0800, Damien Le Moal wrote:
> On 2026/06/10 13:28, raoxu wrote:
> > From: Xu Rao <raoxu@uniontech.com>
> > 
> > JMicron JMS562, as used in QNAP QDA-A2AR RAID1 adapters, may
> > keep the exported ATA device not ready while the array is rebuilding.
> > 
> > In this state, libata may repeatedly try to softreset and classify
> > the fan-out link.  On the affected adapter, this can time out, make
> > PMP/SCR access fail, and eventually disable the fan-out link before
> > the RAID volume is exported.
> > 
> > A failing boot shows the fan-out link failing SRST, PMP access
> > timing out, SCR read failing, and the link being disabled:
> > 
> >   ata4.00: softreset failed (device not ready)
> >   ata4.15: qc timeout after 3000 msecs (cmd 0xe4)
> >   ata4.00: failed to read SCR 0 (Emask=0x4)
> >   ata4.00: failed to recover link after 3 tries, disabling
> > 
> > After that, the root filesystem on the exported RAID volume cannot
> > be found.
> > 
> > Add JMS562 to the existing JMicron PMP quirk that disables LPM,
> > avoids softreset on fan-out links, and assumes an ATA device.  This
> > prevents libata from dropping the exported RAID volume during rebuild
> > recovery.
> > 
> > Signed-off-by: Xu Rao <raoxu@uniontech.com>
> 
> It is really unfortunate that JMicron keeps having these issues. But I do not
> see any way around this, so:

I don't really like that this patch disables LPM unconditionally for all
the fanout links.

However, this PMP chip seems to be of an older generation compared to the
most popular JMicron JMB575 and JMB585, and seems to be connected using
eSATA interface only (which means external port, which means LPM will be
disabled anyway):
https://www.jmicron.com/file/download/1024/JMS562_Product+Brief.pdf


Kind regards,
Niklas