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Date:   Mon, 27 Jan 2020 12:16:30 +0100
From:   Pali =?utf-8?B?Um9ow6Fy?= <pali.rohar@gmail.com>
To:     Sascha Hauer <s.hauer@pengutronix.de>
Cc:     linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org,
        Jens Axboe <axboe@kernel.dk>, kernel@pengutronix.de
Subject: Re: [PATCH v2] libata: Fix retrieving of active qcs
Message-ID: <20200127111630.bqqzhj57tzt7geds@pali>
References: <20191213080408.27032-1-s.hauer@pengutronix.de>
 <20191225181840.ooo6mw5rffghbmu2@pali>
 <20200106081605.ffjz7xy6e24rfcgx@pengutronix.de>
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On Monday 06 January 2020 09:16:05 Sascha Hauer wrote:
> On Wed, Dec 25, 2019 at 07:18:40PM +0100, Pali Rohár wrote:
> > Hello Sascha!
> > 
> > On Friday 13 December 2019 09:04:08 Sascha Hauer wrote:
> > > ata_qc_complete_multiple() is called with a mask of the still active
> > > tags.
> > > 
> > > mv_sata doesn't have this information directly and instead calculates
> > > the still active tags from the started tags (ap->qc_active) and the
> > > finished tags as (ap->qc_active ^ done_mask)
> > > 
> > > Since 28361c40368 the hw_tag and tag are no longer the same and the
> > > equation is no longer valid. In ata_exec_internal_sg() ap->qc_active is
> > > initialized as 1ULL << ATA_TAG_INTERNAL, but in hardware tag 0 is
> > > started and this will be in done_mask on completion. ap->qc_active ^
> > > done_mask becomes 0x100000000 ^ 0x1 = 0x100000001 and thus tag 0 used as
> > > the internal tag will never be reported as completed.
> > > 
> > > This is fixed by introducing ata_qc_get_active() which returns the
> > > active hardware tags and calling it where appropriate.
> > > 
> > > This is tested on mv_sata, but sata_fsl and sata_nv suffer from the same
> > > problem. There is another case in sata_nv that most likely needs fixing
> > > as well, but this looks a little different, so I wasn't confident enough
> > > to change that.
> > 
> > I can confirm that sata_nv.ko does not work in 4.18 (and new) kernel
> > version correctly. More details are in email:
> > 
> > https://lore.kernel.org/linux-ide/20191225180824.bql2o5whougii4ch@pali/T/
> > 
> > I tried this patch and it fixed above problems with sata_nv.ko. It just
> > needs small modification (see below).
> > 
> > So you can add my:
> > 
> > Tested-by: Pali Rohár <pali.rohar@gmail.com>
> > 
> > And I hope that patch would be backported to 4.18 and 4.19 stable
> > branches soon as distributions kernels are broken for machines with
> > these nvidia sata controllers.
> > 
> > Anyway, what is that another case in sata_nv which needs to be fixed
> > too?
> 
> It's in nv_swncq_sdbfis(). Here we have:
> 
> 	sactive = readl(pp->sactive_block);
> 	done_mask = pp->qc_active ^ sactive;
> 
> 	pp->qc_active &= ~done_mask;
> 	pp->dhfis_bits &= ~done_mask;
> 	pp->dmafis_bits &= ~done_mask;
> 	pp->sdbfis_bits |= done_mask;
> 	ata_qc_complete_multiple(ap, ap->qc_active ^ done_mask);
> 
> Sascha

Ok. Are you going to fix also this case?

-- 
Pali Rohár
pali.rohar@gmail.com