Remove the facility for setting the prescaler value at compile time
entirely. It was only used for two SoCs, duplicating the actual value
for one of them and setting sometimes bogus value for another. Make all
MPC8xxx SoCs obtain their actual I2C clock prescaler from a single place
in the code.

Changes from v2:
- left Device Tree compatibles in place
Signed-off-by: Arseny Solokha <asolokha@kb.kras.ru>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

According to the reference manuals for the corresponding SoCs, SEC
frequency ratio configuration is indicated by bit 26 of the POR Device
Status Register 2. Consequently, SEC_CFG bit should be tested by mask 0x20,
not 0x80. Testing the wrong bit leads to selection of wrong I2C clock
prescaler on those SoCs.
Signed-off-by: Arseny Solokha <asolokha@kb.kras.ru>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Commit 8ce795cb ("i2c: mpc: assign the correct prescaler from SVR")
introduced the common helper function for obtaining the actual clock
prescaler value for MPC85xx. However, getting the prescaler for MPC8544
which depends on the SEC frequency ratio on this platform, has been always
performed separately based on the corresponding Device Tree configuration.

Move special handling of MPC8544 into that common helper. Make it dependent
on the SoC version and not on Device Tree compatible node, as is the case
with all other SoCs. Handle MPC8533 the same way which is similar
to MPC8544 in this regard, according to AN2919 "Determining the I2C
Frequency Divider Ratio for SCL".
Signed-off-by: Arseny Solokha <asolokha@kb.kras.ru>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Obtaining the actual I2C clock prescaler value in mpc_i2c_setup_8xxx() only
happens when the clock parameter is set to something other than
MPC_I2C_CLOCK_LEGACY. When the clock parameter is exactly
MPC_I2C_CLOCK_LEGACY, the prescaler parameter is used in arithmetic
division as provided by the caller, resulting in a division by zero
for the majority of processors supported by the module.

Avoid division by zero by obtaining the actual I2C clock prescaler
in mpc_i2c_setup_8xxx() unconditionally regardless of the passed clock
value.
Signed-off-by: Arseny Solokha <asolokha@kb.kras.ru>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

This patch dumps general and master registers at the end of transactions
when debugging is enabled. Previously, registers were only dumped before
submitting new descriptors (at the beginning of transactions).

This helps debugging if some registers change as result of a failed
transaction (e.g. bits are set in the ERRSTS general register).
Signed-off-by: Radu Rendec <radu.rendec@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Make use of the new formula for more precise bus frequencies.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

The formula to generate the desired bus speeds has changed a little over
time. Implement the new formula and allow drivers to opt-in by changing
to this new config set. Ensure in probe that we don't divide by zero.
The returned values on a R-Car H2 (r8a7790/Lager board) match the
suggested values in the datasheet.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Because we will add a second formula soon, put the sanity checks for the
computed results into a separate function.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Start RuntimePM a bit earlier, so we can use it to enable the clock
during probe for frequency calculations. Make sure it is enabled before
calling setup().
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Require the setup callback and move the frequency calculation into it.
This is in preparation for supporting multiple formulas.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

The setup callback will be more generic and, thus, need to be able to
return error codes. Change the return type to 'int' for that.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

For refactoring reasons, we will need this information before the setup
callback. Also, simplify the comment to a oneliner.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

"Slow" GPIOs (usually those connected over an SPI or an I2C bus) are,
well, slow in their operation. It is generally a good idea to avoid
using them for time-critical operation, but sometimes the hardware just
sucks, and the software has to cope. In addition to that, the I2C bus
itself does not actually define any strict timing limits; the bus is
free to go all the way down to DC. The timeouts (and therefore the
slowest acceptable frequency) are present only in SMBus.

The `can_sleep` is IMHO a wrong concept to use here. My SPI-to-quad-UART
chip (MAX14830) is connected via a 26MHz SPI bus, and it happily drives
SCL at 200kHz (5µs pulses) during my benchmarks. That's faster than the
maximal allowed speed of the traditional I2C.

The previous version of this code did not really block operation over
slow GPIO pins, anyway. Instead, it just resorted to printing a warning
with a backtrace each time a GPIO pin was accessed, thereby slowing
things down even more.

Finally, it's not just me. A similar patch was originally submitted in
2015 [1].

[1] https://patchwork.ozlabs.org/patch/450956/Signed-off-by: Jan Kundrát <jan.kundrat@cesnet.cz>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Make sure i2c module clock has been enabled before i2c registers
access.
Signed-off-by: Jun Gao <jun.gao@mediatek.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Add i2c compatible for MT2712. Compare to MT8173 i2c controller,
internal divider of i2c source clock need to be configured for
MT2712 i2c speed calculation.
Signed-off-by: Jun Gao <jun.gao@mediatek.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Add MT2712 i2c binding to binding file. Compare to MT8173 i2c
controller, MT2712 has timing adjust registers which can adjust
the internal divider of i2c source clock, SCL duty cycle, SCL
compare point, start(repeated start) and stop time, SDA change
time.
Signed-off-by: Jun Gao <jun.gao@mediatek.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Merge tag 'at24-4.16-updates-for-wolfram' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux into i2c/for-4.16

"AT24 updates for 4.16 merge window

The driver has been converted to using regmap instead of raw i2c and
smbus calls which shrank the code significantly.

Device tree binding document has been cleaned up. Device tree support in
the driver has been improved and we now support all at24 models as well
as two new DT properties (no-read-rollover and wp-gpios).

We no longer user unreadable magic values for driver data as the way it
was implemented caused problems for some EEPROM models - we switched to
regular structs.

Aside from that, there's a bunch of coding style fixes and minor
improvements all over the place."

Add all supported at24 variants to the of_match table.
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>

Add other variants of at24 EEPROMs we support in the driver to the
list of allowed compatible fallbacks.
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Rob Herring <robh@kernel.org>

Make formatting and style consistent for the entire document.

This patch doesn't change the content of the binding.
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Rob Herring <robh@kernel.org>

Current description of the compatible property for at24 is quite vague.

State explicitly that any "<manufacturer>,<model>" pair is accepted as
long as a correct fallback is used for non-atmel chips.
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Reviewed-by: Rob Herring <robh@kernel.org>

Replace spaces with tabs in the definition of AT24_FLAG_NO_RDROL.

Fixes: 9d404411091c ("eeprom: at24: support eeproms that do not auto-rollover reads")
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

AT24 EEPROMs have a write-protect pin, which - when pulled high -
inhibits writes to the upper quadrant of memory (although it has been
observed that on some chips it disables writing to the entire memory
range).

On some boards, this pin is connected to a GPIO and pulled high by
default, which forces the user to manually change its state before
writing. On linux this means that we either need to hog the line all
the time, or set the GPIO value before writing from outside of the
at24 driver.

Make the driver check if the write-protect GPIO was defined in the
device tree and pull it low whenever writing to the EEPROM.
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

AT24 EEPROMs have a write-protect pin, which - when pulled high -
inhibits writes to the upper quadrant of memory (although it has been
observed that on some chips it disables writing to the entire memory
range).

On some boards, this pin is connected to a GPIO and pulled high by
default, which forces the user to manually change its state before
writing. On linux this means that we either need to hog the line all
the time, or set the GPIO value before writing from outside of the
at24 driver.

Add a new optional property to the device tree binding document, which
allows to specify the GPIO line to which the write-protect pin is
connected.
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>

The chip size passed via devicetree, i2c, or acpi device ids is now no
longer limited to a power of two. So the temporary fix can be removed.
Signed-off-by: Sven Van Asbroeck <svendev@arcx.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

Fundamental properties such as capacity and page size differ among
at24-type chips. But these chips do not have an id register, so this
can't be discovered at runtime.

Traditionally, at24-type eeprom properties were determined in two ways:
- by passing a 'struct at24_platform_data' via platform_data, or
- by naming the chip type in the devicetree, which passes a 'magic
  number' to probe(), which is then converted to a 'struct
  at24_platform_data'.

Recently a bug was discovered because the magic number rounds down all
chip sizes to the lowest power of two. This was addressed by
a work-around commit 5478e478 ("eeprom: at24: correctly set the
size for at24mac402"), with the wish that magic numbers should over
time be converted to structs.

This patch replaces the magic numbers with 'struct at24_chip_data'.
Signed-off-by: Sven Van Asbroeck <svendev@arcx.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

A regmap_config struct is pretty big and declaring two of them
statically just to tweak the reg_bits value adds unnecessary bloat.

Declare the regmap config locally in at24_probe() instead.

Bloat-o-meter output for ARM:

add/remove: 0/2 grow/shrink: 1/0 up/down: 4/-272 (-268)
Function                                     old     new   delta
at24_probe                                  1560    1564      +4
regmap_config_8                              136       -    -136
regmap_config_16                             136       -    -136
Total: Before=7012, After=6744, chg -3.82%
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

There are a couple symbols defined in the driver source file which are
missing the at24_ prefix. This patch fixes that.

For module params: use module_param_named() in order to not break
userspace.
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

Fix issues reported by checkpatch for at24.c.
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

Add the link to my git tree to the at24 section.
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

Some multi-address eeproms in the at24 family may not automatically
roll-over reads to the next slave address. On those eeproms, reads
that straddle slave boundaries will not work correctly.

Solution:
Mark such eeproms with a flag that prevents reads straddling
slave boundaries. Add the AT24_FLAG_NO_RDROL flag to the eeprom
entry in the device_id table, or add 'no-read-rollover' to the
eeprom devicetree entry.

Note that I have not personally enountered an at24 chip that
does not support read rollovers. They may or may not exist.
However, my hardware requires this functionality because of
a quirk.
Signed-off-by: Sven Van Asbroeck <svendev@arcx.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

Adds an optional property for at24 eeproms. This parameterless
property indicates that the multi-address eeprom does not
automatically roll over reads to the next slave address.
Signed-off-by: Sven Van Asbroeck <svendev@arcx.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

The driver gained DT support recently, so we should add the binding docs
in the MAINTAINERS file.
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

This binding documentation is for the at24 driver, so the filename
should reflect it. This avoids confusion because we also have an
"eeprom" driver in Linux but it doesn't support DT even.
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

Remove remaining now unneeded code dealing with SMBUS details.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

Remove the old and now unused read functions.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

Add regmap-based read function and instead of using three different
read functions (standard, mac, serial) use just one and factor out the
read offset adjustment for mac and serial to at24_adjust_read_offset.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

Remove the old and now unused write functions.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

Add a regmap-based write function.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

Change return type of at24_translate_offset to *at24_client to make
member regmap accessible for subsequent patches of this series.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>