Skip to content

L
linux
Switch branch/tag
  1. 07 Dec, 2020 5 commits
  3. 04 Dec, 2020 1 commit
  5. 27 Nov, 2020 2 commits
  7. 25 Nov, 2020 2 commits
  9. 24 Nov, 2020 2 commits
  11. 23 Nov, 2020 2 commits
  13. 20 Nov, 2020 4 commits
    • Serge Semin's avatar
      spi: Take the SPI IO-mutex in the spi_setup() method · 4fae3a58
      Serge Semin authored 
      I've discovered that due to the recent commit 49d7d695 ("spi: dw:
Explicitly de-assert CS on SPI transfer completion") a concurrent usage of
the spidev devices with different chip-selects causes the "SPI transfer
timed out" error. The root cause of the problem has turned to be in a race
condition of the SPI-transfer execution procedure and the spi_setup()
method being called at the same time. In particular in calling the
spi_set_cs(false) while there is an SPI-transfer being executed. In my
case due to the commit cited above all CSs get to be switched off by
calling the spi_setup() for /dev/spidev0.1 while there is an concurrent
SPI-transfer execution performed on /dev/spidev0.0. Of course a situation
of the spi_setup() being called while there is an SPI-transfer being
executed for two different SPI peripheral devices of the same controller
may happen not only for the spidev driver, but for instance for MMC SPI +
some another device, or spi_setup() being called from an SPI-peripheral
probe method while some other device has already been probed and is being
used by a corresponding driver...

Of course I could have provided a fix affecting the DW APB SSI driver
only, for instance, by creating a mutual exclusive access to the set_cs
callback and setting/clearing only the bit responsible for the
corresponding chip-select. But after a short research I've discovered that
the problem most likely affects a lot of the other drivers:
- drivers/spi/spi-sun4i.c - RMW the chip-select register;
- drivers/spi/spi-rockchip.c - RMW the chip-select register;
- drivers/spi/spi-qup.c - RMW a generic force-CS flag in a CSR.
- drivers/spi/spi-sifive.c - set a generic CS-mode flag in a CSR.
- drivers/spi/spi-bcm63xx-hsspi.c - uses an internal mutex to serialize
  the bus config changes, but still isn't protected from the race
  condition described above;
- drivers/spi/spi-geni-qcom.c - RMW a chip-select internal flag and set the
  CS state in HW;
- drivers/spi/spi-orion.c - RMW a chip-select register;
- drivers/spi/spi-cadence.c - RMW a chip-select register;
- drivers/spi/spi-armada-3700.c - RMW a chip-select register;
- drivers/spi/spi-lantiq-ssc.c - overwrites the chip-select register;
- drivers/spi/spi-sun6i.c - RMW a chip-select register;
- drivers/spi/spi-synquacer.c - RMW a chip-select register;
- drivers/spi/spi-altera.c - directly sets the chip-select state;
- drivers/spi/spi-omap2-mcspi.c - RMW an internally cached CS state and
  writes it to HW;
- drivers/spi/spi-mt65xx.c - RMW some CSR;
- drivers/spi/spi-jcore.c - directly sets the chip-selects state;
- drivers/spi/spi-mt7621.c - RMW a chip-select register;

I could have missed some drivers, but a scale of the problem is obvious.
As you can see most of the drivers perform an unprotected
Read-modify-write chip-select register modification in the set_cs callback.
Seeing the spi_setup() function is calling the spi_set_cs() and it can be
executed concurrently with SPI-transfers exec procedure, which also calls
spi_set_cs() in the SPI core spi_transfer_one_message() method, the race
condition of the register modification turns to be obvious.

To sum up the problem denoted above affects each driver for a controller
having more than one chip-select lane and which:
1) performs the RMW to some CS-related register with no serialization;
2) directly disables any CS on spi_set_cs(dev, false).
* the later is the case of the DW APB SSI driver.

The controllers which equipped with a single CS theoretically can also
experience the problem, but in practice will not since normally the
spi_setup() isn't called concurrently with the SPI-transfers executed on
the same SPI peripheral device.

In order to generically fix the denoted bug I'd suggest to serialize an
access to the controller IO by taking the IO mutex in the spi_setup()
callback. The mutex is held while there is an SPI communication going on
on the SPI-bus of the corresponding SPI-controller. So calling the
spi_setup() method and disabling/updating the CS state within it would be
safe while there is no any SPI-transfers being executed. Also note I
suppose it would be safer to protect the spi_controller->setup() callback
invocation too, seeing some of the SPI-controller drivers update a HW
state in there.

Fixes: 49d7d695 ("spi: dw: Explicitly de-assert CS on SPI transfer completion")
Signed-off-by: default avatarSerge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201117094517.5654-1-Sergey.Semin@baikalelectronics.ruSigned-off-by: default avatarMark Brown <broonie@kernel.org>
      4fae3a58
    • Uwe Kleine-König's avatar
      spi: Warn when a driver's remove callback returns an error · 7795d475
      Uwe Kleine-König authored 
      The driver core ignores the return value of struct device_driver::remove
(because in general there is nothing that can be done about that). So
add a warning when an spi driver returns an error.

This simplifies the quest to make struct device_driver::remove return void.
A consequent change would be to make struct spi_driver::remove return void,
but I'm keeping this quest for later (or someone else).
Signed-off-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20201119161604.2633521-3-u.kleine-koenig@pengutronix.deSigned-off-by: default avatarMark Brown <broonie@kernel.org>
      7795d475
    • Uwe Kleine-König's avatar
      spi: Use bus_type functions for probe, remove and shutdown · 9db34ee6
      Uwe Kleine-König authored 
      The eventual goal is to get rid of the callbacks in struct
device_driver. Other than not using driver callbacks there should be no
side effect of this patch.
Signed-off-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20201119161604.2633521-2-u.kleine-koenig@pengutronix.deSigned-off-by: default avatarMark Brown <broonie@kernel.org>
      9db34ee6
    • Uwe Kleine-König's avatar
      spi: fix resource leak for drivers without .remove callback · 440408db
      Uwe Kleine-König authored 
      Consider an spi driver with a .probe but without a .remove callback (e.g.
rtc-ds1347). The function spi_drv_probe() is called to bind a device and
so dev_pm_domain_attach() is called. As there is no remove callback
spi_drv_remove() isn't called at unbind time however and so calling
dev_pm_domain_detach() is missed and the pm domain keeps active.

To fix this always use both spi_drv_probe() and spi_drv_remove() and
make them handle the respective callback not being set. This has the
side effect that for a (hypothetical) driver that has neither .probe nor
remove the clk and pm domain setup is done.

Fixes: 33cf00e5 ("spi: attach/detach SPI device to the ACPI power domain")
Signed-off-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20201119161604.2633521-1-u.kleine-koenig@pengutronix.deSigned-off-by: default avatarMark Brown <broonie@kernel.org>
      440408db
  15. 18 Nov, 2020 1 commit
  17. 17 Nov, 2020 3 commits
  19. 16 Nov, 2020 4 commits
  21. 13 Nov, 2020 1 commit
  23. 12 Nov, 2020 10 commits
  25. 11 Nov, 2020 3 commits
GitLab Nexedi Edition | About GitLab | About Nexedi | 沪ICP备2021021310号-2 | 沪ICP备2021021310号-7