linux-kernel - Re: [PATCH v1 1/3] i2c: tegra: Support atomic transfers

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Message-ID: <20191213152017.GA293199@ulmo>
Date:   Fri, 13 Dec 2019 16:20:17 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Jonathan Hunter <jonathanh@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Wolfram Sang <wsa@...-dreams.de>, linux-i2c@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/3] i2c: tegra: Support atomic transfers

On Fri, Dec 13, 2019 at 06:15:12PM +0300, Dmitry Osipenko wrote:
> 13.12.2019 18:12, Thierry Reding пишет:
> > On Fri, Dec 13, 2019 at 02:34:26AM +0300, Dmitry Osipenko wrote:
> >> System shutdown may happen with interrupts being disabled and in this case
> >> I2C core rejects transfers if atomic transfer isn't supported by driver.
> >>
> >> There were several occurrences where I found my Nexus 7 completely
> >> discharged despite of being turned off and then one day I spotted this in
> >> the log:
> >>
> >>  reboot: Power down
> >>  ------------[ cut here ]------------
> >>  WARNING: CPU: 0 PID: 1 at drivers/i2c/i2c-core.h:40 i2c_transfer+0x95/0x9c
> >>  No atomic I2C transfer handler for 'i2c-1'
> >>  Modules linked in: tegra30_devfreq
> >>  CPU: 0 PID: 1 Comm: systemd-shutdow Not tainted 5.4.0-next-20191202-00120-gf7ecd80fb803-dirty #3195
> >>  Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
> >>  [<c010e4b5>] (unwind_backtrace) from [<c010a0fd>] (show_stack+0x11/0x14)
> >>  [<c010a0fd>] (show_stack) from [<c09995e5>] (dump_stack+0x85/0x94)
> >>  [<c09995e5>] (dump_stack) from [<c011f3d1>] (__warn+0xc1/0xc4)
> >>  [<c011f3d1>] (__warn) from [<c011f691>] (warn_slowpath_fmt+0x61/0x78)
> >>  [<c011f691>] (warn_slowpath_fmt) from [<c069a8dd>] (i2c_transfer+0x95/0x9c)
> >>  [<c069a8dd>] (i2c_transfer) from [<c05667f1>] (regmap_i2c_read+0x4d/0x6c)
> >>  [<c05667f1>] (regmap_i2c_read) from [<c0563601>] (_regmap_raw_read+0x99/0x1cc)
> >>  [<c0563601>] (_regmap_raw_read) from [<c0563757>] (_regmap_bus_read+0x23/0x38)
> >>  [<c0563757>] (_regmap_bus_read) from [<c056293d>] (_regmap_read+0x3d/0xfc)
> >>  [<c056293d>] (_regmap_read) from [<c0562d3b>] (_regmap_update_bits+0x87/0xc4)
> >>  [<c0562d3b>] (_regmap_update_bits) from [<c0563add>] (regmap_update_bits_base+0x39/0x50)
> >>  [<c0563add>] (regmap_update_bits_base) from [<c056fd39>] (max77620_pm_power_off+0x29/0x2c)
> >>  [<c056fd39>] (max77620_pm_power_off) from [<c013bbdd>] (__do_sys_reboot+0xe9/0x170)
> >>  [<c013bbdd>] (__do_sys_reboot) from [<c0101001>] (ret_fast_syscall+0x1/0x28)
> >>  Exception stack(0xde907fa8 to 0xde907ff0)
> >>  7fa0:                   00000000 00000000 fee1dead 28121969 4321fedc 00000000
> >>  7fc0: 00000000 00000000 00000000 00000058 00000000 00000000 00000000 00000000
> >>  7fe0: 0045adf0 bed9abb8 004444a0 b6c666d0
> >>  ---[ end trace bdd18f87595b1a5e ]---
> >>
> >> The atomic transferring is implemented by enforcing PIO mode for the
> >> transfer and by polling interrupt status until transfer is completed or
> >> failed.
> >>
> >> Now system shuts down properly every time.
> >>
> >> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> >> ---
> >>  drivers/i2c/busses/i2c-tegra.c | 95 +++++++++++++++++++++++++++++++---
> >>  1 file changed, 88 insertions(+), 7 deletions(-)
> > 
> > I ran this on the test farm and the results are all green, so:
> > 
> > Tested-by: Thierry Reding <treding@...dia.com>
> > 
> 
> Thanks!
> 
> Does the farm test board's shut down by verifying the
> hardware's power state?

No, that's not something we test. I was primarily running this to make
sure we don't regress anywhere else.

Thierry

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