linux/drivers/i2c
Mika Westerberg 56d4b8a24c i2c: designware: Do not use parameters from ACPI on Dell Inspiron 7348
ACPI SSCN/FMCN methods were originally added because then the platform can
provide the most accurate HCNT/LCNT values to the driver. However, this
seems not to be true for Dell Inspiron 7348 where using these causes the
touchpad to fail in boot:

  i2c_hid i2c-DLL0675:00: failed to retrieve report from device.
  i2c_designware INT3433:00: i2c_dw_handle_tx_abort: lost arbitration
  i2c_hid i2c-DLL0675:00: failed to retrieve report from device.
  i2c_designware INT3433:00: controller timed out

The values received from ACPI are (in fast mode):

  HCNT: 72
  LCNT: 160

this translates to following timings (input clock is 100MHz on Broadwell):

  tHIGH: 720 ns (spec min 600 ns)
  tLOW: 1600 ns (spec min 1300 ns)
  Bus period: 2920 ns (assuming 300 ns tf and tr)
  Bus speed: 342.5 kHz

Both tHIGH and tLOW are within the I2C specification.

The calculated values when ACPI parameters are not used are (in fast mode):

  HCNT: 87
  LCNT: 159

which translates to:

  tHIGH: 870 ns (spec min 600 ns)
  tLOW: 1590 ns (spec min 1300 ns)
  Bus period 3060 ns (assuming 300 ns tf and tr)
  Bus speed 326.8 kHz

These values are also within the I2C specification.

Since both ACPI and calculated values meet the I2C specification timing
requirements it is hard to say why the touchpad does not function properly
with the ACPI values except that the bus speed is higher in this case (but
still well below the max 400kHz).

Solve this by adding DMI quirk to the driver that disables using ACPI
parameters on this particulare machine.

Reported-by: Pavel Roskin <plroskin@gmail.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Tested-by: Pavel Roskin <plroskin@gmail.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
2015-10-18 14:11:08 +02:00
..
algos i2c: algo-pca: fix typo in comment 2015-06-01 08:41:19 +09:00
busses i2c: designware: Do not use parameters from ACPI on Dell Inspiron 7348 2015-10-18 14:11:08 +02:00
muxes i2c: mux: reg Change ioread endianness for readback 2015-09-03 11:58:42 +02:00
Kconfig kconfig: use bool instead of boolean for type definition attributes 2015-01-07 13:08:04 +01:00
Makefile i2c: slave-eeprom: add eeprom simulator driver 2014-12-11 22:25:54 +01:00
i2c-boardinfo.c i2c: remove FSF address 2014-11-07 18:35:33 +01:00
i2c-core.c i2c: return probe deferred status on dev_pm_domain_attach 2015-10-15 13:35:32 +02:00
i2c-core.h i2c: remove FSF address 2014-11-07 18:35:33 +01:00
i2c-dev.c i2c: remove FSF address 2014-11-07 18:35:33 +01:00
i2c-mux.c i2c: mux: Use __i2c_transfer() instead of calling parent's master_xfer() 2015-06-17 14:35:37 +02:00
i2c-slave-eeprom.c i2c: Drop owner assignment from i2c_driver 2015-08-10 08:37:35 +02:00
i2c-smbus.c i2c: smbus: fix typo in commet 2015-06-01 08:41:26 +09:00
i2c-stub.c i2c: remove FSF address 2014-11-07 18:35:33 +01:00