Make trickle-resistor-ohms optional for charging setups that do not
require specifying ROUT bits (specifying the resistor value between Vcc
and Vbackup). In order to allow specifying that, introduce
requires_trickle_resistor per chip.
Signed-off-by: Bastian Krause <bst@pengutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200917183246.19446-6-bst@pengutronix.de

DS13XX_TRICKLE_CHARGER_MAGIC sets the trickle-charge select (TCS) bits
(7..4). The datasheet of Maxim Integrated's DS1339 [1] for instance
reads:

"To prevent accidental enabling, only a pattern on 1010 enables the
trickle charger. All other patterns disable the trickle charger."

Since not all RTCs connected to a backup battery or supercap use these
bits DS13XX_TRICKLE_CHARGER_MAGIC should not get applied for all charger
setups unconditionally.
Epson's RX8130 is such an example: Instead of TCS bits "SMPTSEL1",
"SMPTSEL0",  "CHGEN" and "INIEN" are expected as bit 7..4.

DS1339 and DS1340 are currently the only RTCs in the ds1307 driver that
apply DS13XX_TRICKLE_CHARGER_MAGIC to their setup register value. So
apply DS13XX_TRICKLE_CHARGER_MAGIC in do_trickle_setup_ds1339() which
is used by both RTCs.

[1] https://datasheets.maximintegrated.com/en/ds/DS1339-DS1339U.pdf
[2] https://support.epson.biz/td/api/doc_check.php?dl=app_RX8130CESigned-off-by: Bastian Krause <bst@pengutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200917183246.19446-5-bst@pengutronix.de

Epson's RX8130 was not charged before. A related patch will allow
optional charging.
Signed-off-by: Bastian Krause <bst@pengutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200917183246.19446-4-bst@pengutronix.de

trickle-diode-disable is deprecated, so reflect that in the driver's
binding and add the new aux-voltage-chargeable.
Signed-off-by: Bastian Krause <bst@pengutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200917183246.19446-3-bst@pengutronix.de

Some RTCs can be equipped with a chargeable battery or supercap.
Every RTC allowing this whose driver's implement it are charged by
default. To disable this the trickle-diode-disable flag exists.

If a driver did not support charging and some time later one wants to
add that feature, there is currently no way to do it without breaking
dt backwards compatibility. RTCs on boards without the
trickle-diode-disable flag in their device tree would suddenly charge
their battery/supercap which is a change in behavior.

Change that by introducing aux-voltage-chargeable, not as a flag but as
a uint32 enum allowing to set "do not charge" (0) or "charge" (1). This
dt property is optional, so we can now distinguish these cases.

Care must be taken to support the old behavior for device trees without
aux-voltage-chargeable nonetheless to stay compatible.
Signed-off-by: Bastian Krause <bst@pengutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200917183246.19446-2-bst@pengutronix.de

Fix a bug when not specify interrupts property in dts
as follows,
    rtc-pcf2127-i2c 1-0051: failed to request alarm irq
    rtc-pcf2127-i2c: probe of 1-0051 failed with error -22
Signed-off-by: Biwen Li <biwen.li@nxp.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200915073213.12779-1-biwen.li@oss.nxp.com

ds1685_rtc_begin_data_access() tried to access an extended register before
enabling access to it by switching to bank 1. Depending on content in NVRAM
this could lead to an endless loop. While at it fix also switch back to
bank 0 in ds1685_rtc_end_data_access().
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: Joshua Kinard <kumba@gentoo.org>
Link: https://lore.kernel.org/r/20200910084124.138560-1-tsbogend@alpha.franken.de

The only usage of st_rtc_ops is to assign its address to the ops field
in the rtc_device struct. which is a const pointer. Make it const to
allow the compiler to put it in read-only memory.
Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200913122644.35515-1-rikard.falkeborn@gmail.com

We don't need to check the time range manually in set_time(), we can
use range_min and range_max exposed by struct rtc_device.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200914154601.32245-15-brgl@bgdev.pl

This driver requires SMBUS to work. We can relax this requirement if we
switch to using i2c regmap and let the regmap sub-system figure out how
to talk to the bus.

This also has the advantage of shrinking the code for register updates.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200914154601.32245-14-brgl@bgdev.pl

We should generally use probe_new instead of probe when registering i2c
drivers. Convert rx8010 to using it.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200914154601.32245-13-brgl@bgdev.pl

Use devm_rtc_allocate_device() + rtc_register_device() instead of the
deprecated devm_rtc_device_register().
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200914154601.32245-12-brgl@bgdev.pl

Using the size of the variable is preferred over using the size of its
type when allocating memory. Convert the call to devm_kzalloc() in
probe().
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200914154601.32245-11-brgl@bgdev.pl

Simple 'dev' looks better then repeated &client->dev and has the added
benefit of avoiding unnecessary line breaks.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200914154601.32245-10-brgl@bgdev.pl

The 'err' local variable in rx8010_init_client() doesn't need to be
initialized.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200914154601.32245-9-brgl@bgdev.pl

The time buffer len is used directly in this driver. For readability
it's better to define it as the difference between the date register
offsets and use sizeof() whenever referencing it.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200914154601.32245-8-brgl@bgdev.pl

All other functions in this driver use 'err' for integer return values.
Do the same in rx8010_set_time() for consistency.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200914154601.32245-7-brgl@bgdev.pl

The define values in this driver are close to their names and they are
separated by spaces. Use tabs instead and align all defines.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200914154601.32245-6-brgl@bgdev.pl

Move local variables of the same type into a single line for better
readability.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200914154601.32245-5-brgl@bgdev.pl

Remove brackets wherever they guard a single line.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200914154601.32245-4-brgl@bgdev.pl

Remove an unnecessary newline after requesting the interrupt.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200914154601.32245-3-brgl@bgdev.pl

The way the driver is implemented is buggy for the (admittedly unlikely)
use case where there are two RTCs with one having an interrupt configured
and the second not. This is caused by the fact that we use a global
rtc_class_ops struct which we modify depending on whether the irq number
is present or not.

Fix it by using two const ops structs with and without alarm operations.
While at it: not being able to request a configured interrupt is an error
so don't ignore it and bail out of probe().

Fixes: ed13d89b ("rtc: Add Epson RX8010SJ RTC driver")
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200914154601.32245-2-brgl@bgdev.pl

Common pattern of handling deferred probe can be simplified with
dev_err_probe().  Less code and the error value gets printed.
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200830080937.14367-1-krzk@kernel.org

Original device id would conflict with crypto driver, change it.
Signed-off-by: Peng Ma <peng.ma@nxp.com>
Signed-off-by: Ran Wang <ran.wang_1@nxp.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200818063609.39859-1-ran.wang_1@nxp.com

Ensure the OSF flag is cleared on the DS1388 when the clock is set.

Fixes: df11b323 ("rtc: ds1307: handle oscillator failure flags for ds1388 variant")
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200818013543.4283-1-chris.packham@alliedtelesis.co.nz

Similar to the other variants the DS1388 has a bit to stop the
oscillator to reduce the power consumption from VBAT. Ensure that the
oscillator is enabled when the system is up.
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200816235731.21071-1-chris.packham@alliedtelesis.co.nz

Reduce boilerplate by using the module_platform_driver() helper.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200814110731.29029-4-geert+renesas@glider.be

rs5c313_rtc_init() calls platform_driver_register(), and initializes the
hardware.  This is wrong because of two reasons:
  1. As soon as the driver has been registered, the device may be
     probed.  If devm_rtc_device_register() is called before hardware
     initialization, reading the current time will fail:

	rs5c313 rs5c313: rs5c313_rtc_read_time: timeout error
	rs5c313 rs5c313: registered as rtc0
	rs5c313 rs5c313: rs5c313_rtc_read_time: timeout error
	rs5c313 rs5c313: hctosys: unable to read the hardware clock

  2. If the platform device does not exist, the driver will still write
     to a hardware device that may not be present.

Fix this by moving the hardware initialization sequence to the driver's
.probe() method.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200814110731.29029-3-geert+renesas@glider.be

Commit 284e2fa1 ("rtc: rtc-rs5c313: use
devm_rtc_device_register()"), removed the last user of the
driver-specific data.  Hence there is no longer a need to set it.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200814110731.29029-2-geert+renesas@glider.be

cmos_read_alarm() may leave certain fields of a struct rtc_wkalrm
untouched; therefore, these fields contain garbage if not properly
initialized, leading to inconsistent values when converting into
time64_t. This patch to zero initialize the struct before calling
cmos_read_alarm().

Note that this patch is not intended to produce a correct time64_t, it
is only to produce a consistent value. In the case of suspend/resume, a
correct time64_t is not necessary; a consistent value is sufficient to
correctly perform an equality test for t_current_expires and
t_saved_expires. Logic to deduce a correct time64_t is expensive and
hence should be avoided.
Signed-off-by: Victor Ding <victording@google.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200814191654.v2.1.Iaf7638a2f2a87ff68d85fcb8dec615e41340c97f@changeid

Pull io_uring fixes from Jens Axboe:
 "A few differerent things in here.

  Seems like syzbot got some more io_uring bits wired up, and we got a
  handful of reports and the associated fixes are in here.

  General fixes too, and a lot of them marked for stable.

  Lastly, a bit of fallout from the async buffered reads, where we now
  more easily trigger short reads. Some applications don't really like
  that, so the io_read() code now handles short reads internally, and
  got a cleanup along the way so that it's now easier to read (and
  documented). We're now passing tests that failed before"

* tag 'io_uring-5.9-2020-08-15' of git://git.kernel.dk/linux-block:
  io_uring: short circuit -EAGAIN for blocking read attempt
  io_uring: sanitize double poll handling
  io_uring: internally retry short reads
  io_uring: retain iov_iter state over io_read/io_write calls
  task_work: only grab task signal lock when needed
  io_uring: enable lookup of links holding inflight files
  io_uring: fail poll arm on queue proc failure
  io_uring: hold 'ctx' reference around task_work queue + execute
  fs: RWF_NOWAIT should imply IOCB_NOIO
  io_uring: defer file table grabbing request cleanup for locked requests
  io_uring: add missing REQ_F_COMP_LOCKED for nested requests
  io_uring: fix recursive completion locking on oveflow flush
  io_uring: use TWA_SIGNAL for task_work uncondtionally
  io_uring: account locked memory before potential error case
  io_uring: set ctx sq/cq entry count earlier
  io_uring: Fix NULL pointer dereference in loop_rw_iter()
  io_uring: add comments on how the async buffered read retry works
  io_uring: io_async_buf_func() need not test page bit

Commit 1355c31e ("asm-generic: pgalloc: provide generic pmd_alloc_one()
and pmd_free_one()") converted parisc to use generic version of
pmd_alloc_one() but it missed the fact that parisc uses order-1 pages for
PMD.

Restore the original version of pmd_alloc_one() for parisc, just use
GFP_PGTABLE_KERNEL that implies __GFP_ZERO instead of GFP_KERNEL and
memset.

Fixes: 1355c31e ("asm-generic: pgalloc: provide generic pmd_alloc_one() and pmd_free_one()")
Reported-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Tested-by: Meelis Roos <mroos@linux.ee>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Link: https://lkml.kernel.org/r/9f2b5ebd-e4a4-0fa1-6cd3-4b9f6892d1ad@linux.eeSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull block fixes from Jens Axboe:
 "A few fixes on the block side of things:

   - Discard granularity fix (Coly)

   - rnbd cleanups (Guoqing)

   - md error handling fix (Dan)

   - md sysfs fix (Junxiao)

   - Fix flush request accounting, which caused an IO slowdown for some
     configurations (Ming)

   - Properly propagate loop flag for partition scanning (Lennart)"

* tag 'block-5.9-2020-08-14' of git://git.kernel.dk/linux-block:
  block: fix double account of flush request's driver tag
  loop: unset GENHD_FL_NO_PART_SCAN on LOOP_CONFIGURE
  rnbd: no need to set bi_end_io in rnbd_bio_map_kern
  rnbd: remove rnbd_dev_submit_io
  md-cluster: Fix potential error pointer dereference in resize_bitmaps()
  block: check queue's limits.discard_granularity in __blkdev_issue_discard()
  md: get sysfs entry after redundancy attr group create

Pull RISC-V fix from Palmer Dabbelt:
 "I collected a single fix during the merge window: we managed to break
  the early trap setup on !MMU, this fixes it"

* tag 'riscv-for-linus-5.9-mw1' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
  riscv: Setup exception vector for nommu platform

Pull arch/sh updates from Rich Felker:
 "Cleanup, SECCOMP_FILTER support, message printing fixes, and other
  changes to arch/sh"

* tag 'sh-for-5.9' of git://git.libc.org/linux-sh: (34 commits)
  sh: landisk: Add missing initialization of sh_io_port_base
  sh: bring syscall_set_return_value in line with other architectures
  sh: Add SECCOMP_FILTER
  sh: Rearrange blocks in entry-common.S
  sh: switch to copy_thread_tls()
  sh: use the generic dma coherent remap allocator
  sh: don't allow non-coherent DMA for NOMMU
  dma-mapping: consolidate the NO_DMA definition in kernel/dma/Kconfig
  sh: unexport register_trapped_io and match_trapped_io_handler
  sh: don't include <asm/io_trapped.h> in <asm/io.h>
  sh: move the ioremap implementation out of line
  sh: move ioremap_fixed details out of <asm/io.h>
  sh: remove __KERNEL__ ifdefs from non-UAPI headers
  sh: sort the selects for SUPERH alphabetically
  sh: remove -Werror from Makefiles
  sh: Replace HTTP links with HTTPS ones
  arch/sh/configs: remove obsolete CONFIG_SOC_CAMERA*
  sh: stacktrace: Remove stacktrace_ops.stack()
  sh: machvec: Modernize printing of kernel messages
  sh: pci: Modernize printing of kernel messages
  ...

One case was missed in the short IO retry handling, and that's hitting
-EAGAIN on a blocking attempt read (eg from io-wq context). This is a
problem on sockets that are marked as non-blocking when created, they
don't carry any REQ_F_NOWAIT information to help us terminate them
instead of perpetually retrying.

Fixes: 227c0c96 ("io_uring: internally retry short reads")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

There's a bit of confusion on the matching pairs of poll vs double poll,
depending on if the request is a pure poll (IORING_OP_POLL_ADD) or
poll driven retry.

Add io_poll_get_double() that returns the double poll waitqueue, if any,
and io_poll_get_single() that returns the original poll waitqueue. With
that, remove the argument to io_poll_remove_double().

Finally ensure that wait->private is cleared once the double poll handler
has run, so that remove knows it's already been seen.

Cc: stable@vger.kernel.org # v5.8
Reported-by: syzbot+7f617d4a9369028b8a2c@syzkaller.appspotmail.com
Fixes: 18bceab1 ("io_uring: allow POLL_ADD with double poll_wait() users")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Pull more perf tools updates from Arnaldo Carvalho de Melo:
 "Fixes:
   - Fixes for 'perf bench numa'.

   - Always memset source before memcpy in 'perf bench mem'.

   - Quote CC and CXX for their arguments to fix build in environments
     using those variables to pass more than just the compiler names.

   - Fix module symbol processing, addressing regression detected via
     "perf test".

   - Allow multiple probes in record+script_probe_vfs_getname.sh 'perf
     test' entry.

  Improvements:
   - Add script to autogenerate socket family name id->string table from
     copy of kernel header, used so far in 'perf trace'.

   - 'perf ftrace' improvements to provide similar options for this
     utility so that one can go from 'perf record', 'perf trace', etc to
     'perf ftrace' just by changing the name of the subcommand.

   - Prefer new "sched:sched_waking" trace event when it exists in 'perf
     sched' post processing.

   - Update POWER9 metrics to utilize other metrics.

   - Fall back to querying debuginfod if debuginfo not found locally.

  Miscellaneous:
   - Sync various kvm headers with kernel sources"

* tag 'perf-tools-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux: (40 commits)
  perf ftrace: Make option description initials all capital letters
  perf build-ids: Fall back to debuginfod query if debuginfo not found
  perf bench numa: Remove dead code in parse_nodes_opt()
  perf stat: Update POWER9 metrics to utilize other metrics
  perf ftrace: Add change log
  perf: ftrace: Add set_tracing_options() to set all trace options
  perf ftrace: Add option --tid to filter by thread id
  perf ftrace: Add option -D/--delay to delay tracing
  perf: ftrace: Allow set graph depth by '--graph-opts'
  perf ftrace: Add support for trace option tracing_thresh
  perf ftrace: Add option 'verbose' to show more info for graph tracer
  perf ftrace: Add support for tracing option 'irq-info'
  perf ftrace: Add support for trace option funcgraph-irqs
  perf ftrace: Add support for trace option sleep-time
  perf ftrace: Add support for tracing option 'func_stack_trace'
  perf tools: Add general function to parse sublevel options
  perf ftrace: Add option '--inherit' to trace children processes
  perf ftrace: Show trace column header
  perf ftrace: Add option '-m/--buffer-size' to set per-cpu buffer size
  perf ftrace: Factor out function write_tracing_file_int()
  ...

Pull x86 fixes from Ingo Molnar:
 "Misc fixes and small updates all around the place:

   - Fix mitigation state sysfs output

   - Fix an FPU xstate/sxave code assumption bug triggered by
     Architectural LBR support

   - Fix Lightning Mountain SoC TSC frequency enumeration bug

   - Fix kexec debug output

   - Fix kexec memory range assumption bug

   - Fix a boundary condition in the crash kernel code

   - Optimize porgatory.ro generation a bit

   - Enable ACRN guests to use X2APIC mode

   - Reduce a __text_poke() IRQs-off critical section for the benefit of
     PREEMPT_RT"

* tag 'x86-urgent-2020-08-15' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/alternatives: Acquire pte lock with interrupts enabled
  x86/bugs/multihit: Fix mitigation reporting when VMX is not in use
  x86/fpu/xstate: Fix an xstate size check warning with architectural LBRs
  x86/purgatory: Don't generate debug info for purgatory.ro
  x86/tsr: Fix tsc frequency enumeration bug on Lightning Mountain SoC
  kexec_file: Correctly output debugging information for the PT_LOAD ELF header
  kexec: Improve & fix crash_exclude_mem_range() to handle overlapping ranges
  x86/crash: Correct the address boundary of function parameters
  x86/acrn: Remove redundant chars from ACRN signature
  x86/acrn: Allow ACRN guest to use X2APIC mode