linux-kernel - Re: [PATCH 0/4] mmc: meson-gx: chained descriptor fixup and improvements

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Date:   Wed, 02 Jan 2019 13:46:19 +0100
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Carlo Caione <carlo@...one.org>,
        Kevin Hilman <khilman@...libre.com>,
        linux-amlogic@...ts.infradead.org, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] mmc: meson-gx: chained descriptor fixup and
 improvements

On Sat, 2018-12-22 at 18:28 +0100, Martin Blumenstingl wrote:
> Hi Jerome,
> 
> On Thu, Dec 6, 2018 at 4:18 PM Jerome Brunet <jbrunet@...libre.com> wrote:
> > The goal of the patchset was mainly to address the following warning:
> > 
> > WARNING: CPU: 0 PID: 0 at /usr/src/kernel/drivers/mmc/host/meson-gx-
> > mmc.c:1025 meson_mmc_irq+0xc0/0x1e0
> > Modules linked in: crc32_ce crct10dif_ce ipv6 overlay
> > CPU: 0 PID: 0 Comm: swapper/0 Tainted: G        W         4.19.1 #1
> > Hardware name: Some A113 Board (DT)
> > pstate: 40000085 (nZcv daIf -PAN -UAO)
> > pc : meson_mmc_irq+0xc0/0x1e0
> > lr : __handle_irq_event_percpu+0x70/0x180
> > sp : ffff000008003980
> > x29: ffff000008003980 x28: 0000000000000000
> > [...]
> > x1 : ffff80001a71bd40 x0 : 0000000000000000
> > Call trace:
> >  meson_mmc_irq+0xc0/0x1e0
> >  __handle_irq_event_percpu+0x70/0x180
> >  handle_irq_event_percpu+0x34/0x88
> >  handle_irq_event+0x48/0x78
> >  handle_fasteoi_irq+0xa0/0x180
> >  generic_handle_irq+0x24/0x38
> >  __handle_domain_irq+0x5c/0xb8
> >  gic_handle_irq+0x58/0xa8
> > 
> > This happens when using the chained descriptor mode. If there is an
> > error, we call mmc_request_done(), loosing any reference to the cmd. It
> > turns out that the chained descriptor does really stops when we do so, at
> > least not completly. Most of the time, it can be seen with this harmless
> > warning because the descriptor will raise another unexpected IRQ. On rare
> > occasion, it will completly break the MMC.
> > 
> > This is mostly adressed by patch #1.
> > With this fixed, I took (yet) another look at the ultra-high speed modes
> > and the tuning.
> > 
> > I came up with new settings in patch 3 and 4. I've tested them on eMMC,
> > sdcard and sdio on the following platforms:
> >  * gxbb p200
> >  * gxl p230, libretech (eMMC only), kvim.
> >  * axg s400
> > 
> > So far, these new settings seems to be working great but I think it
> > would be nice if others could test this and provide their feedback.
> > This why  patch 3 and 4 are RFT tagged.
> > 
> > Jerome Brunet (4):
> >   mmc: meson-gx: make sure the descriptor is stopped on errors
> >   mmc: meson-gx: remove useless lock
> >   mmc: meson-gx: align default phase on soc vendor tree
> >   mmc: meson-gx: add signal resampling
> I gave all four patches a go on my Khadas VIM2 Basic (16GB eMMC).
> regardless of whether I have your patch applied or not: eMMC
> sporadically fails tuning (if I reboot the board a few times it starts
> to work)
> [    4.172686] mmc1: tuning execution failed: -5
> [    4.182535] mmc1: error -5 whilst initialising MMC card

Damn ...

This particular device is set to use hs400 ATM. Could you try with hs200 only
? (removing mmc-hs400-1_8v from meson-gxm-khadas-vim2.dts) 

I might be wrong but I think tuning is supposed to be done with hs200, before
activating DDR mode to switch to hs400. In theory, removing hs400 should not
change anything (so I expect the tuning to still fail) but it is worth
checking.

> 
> I'm not sure if this issue is specific to my Khadas VIM2 so this is
> *not* a nack for your patches.

I'll check if I can get my hands on this device.

When cooking this series, I tried another trick which was cycling on the
resampling delays (see ADJUST_ADJ_DELAY_MASK). At the time, I could not see
any significant improvement while doing it, so I dropped it.

If possible. could you check if any particular value in this field, between 0
and 5, makes things any better ?

Alternatively, if you find another combination of phase for the mmc_clk and
tx_clk that works better for this device, feel free to let me know. Maybe we
can work something out.

Cheers

> 
> 
> Regards
> Martin