ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

3 files changed, 254 insertions, 0 deletions

diff --git a/Documentation/driver-api/memory-devices/index.rst b/Documentation/driver-api/memory-devices/index.rst
new file mode 100644
index 000000000..3b6308113
--- /dev/null
+++ b/Documentation/driver-api/memory-devices/index.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=========================
+Memory Controller drivers
+=========================
+
+.. toctree::
+    :maxdepth: 1
+
+    ti-emif
+    ti-gpmc
diff --git a/Documentation/driver-api/memory-devices/ti-emif.rst b/Documentation/driver-api/memory-devices/ti-emif.rst
new file mode 100644
index 000000000..dea2ad9bc
--- /dev/null
+++ b/Documentation/driver-api/memory-devices/ti-emif.rst
@@ -0,0 +1,64 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============================
+TI EMIF SDRAM Controller Driver
+===============================
+
+Author
+======
+Aneesh V <aneesh@ti.com>
+
+Location
+========
+driver/memory/emif.c
+
+Supported SoCs:
+===============
+TI OMAP44xx
+TI OMAP54xx
+
+Menuconfig option:
+==================
+Device Drivers
+	Memory devices
+		Texas Instruments EMIF driver
+
+Description
+===========
+This driver is for the EMIF module available in Texas Instruments
+SoCs. EMIF is an SDRAM controller that, based on its revision,
+supports one or more of DDR2, DDR3, and LPDDR2 SDRAM protocols.
+This driver takes care of only LPDDR2 memories presently. The
+functions of the driver includes re-configuring AC timing
+parameters and other settings during frequency, voltage and
+temperature changes
+
+Platform Data (see include/linux/platform_data/emif_plat.h)
+===========================================================
+DDR device details and other board dependent and SoC dependent
+information can be passed through platform data (struct emif_platform_data)
+
+- DDR device details: 'struct ddr_device_info'
+- Device AC timings: 'struct lpddr2_timings' and 'struct lpddr2_min_tck'
+- Custom configurations: customizable policy options through
+  'struct emif_custom_configs'
+- IP revision
+- PHY type
+
+Interface to the external world
+===============================
+EMIF driver registers notifiers for voltage and frequency changes
+affecting EMIF and takes appropriate actions when these are invoked.
+
+- freq_pre_notify_handling()
+- freq_post_notify_handling()
+- volt_notify_handling()
+
+Debugfs
+=======
+The driver creates two debugfs entries per device.
+
+- regcache_dump : dump of register values calculated and saved for all
+  frequencies used so far.
+- mr4 : last polled value of MR4 register in the LPDDR2 device. MR4
+  indicates the current temperature level of the device.
diff --git a/Documentation/driver-api/memory-devices/ti-gpmc.rst b/Documentation/driver-api/memory-devices/ti-gpmc.rst
new file mode 100644
index 000000000..b1bb86871
--- /dev/null
+++ b/Documentation/driver-api/memory-devices/ti-gpmc.rst
@@ -0,0 +1,179 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+========================================
+GPMC (General Purpose Memory Controller)
+========================================
+
+GPMC is an unified memory controller dedicated to interfacing external
+memory devices like
+
+ * Asynchronous SRAM like memories and application specific integrated
+   circuit devices.
+ * Asynchronous, synchronous, and page mode burst NOR flash devices
+   NAND flash
+ * Pseudo-SRAM devices
+
+GPMC is found on Texas Instruments SoC's (OMAP based)
+IP details: https://www.ti.com/lit/pdf/spruh73 section 7.1
+
+
+GPMC generic timing calculation:
+================================
+
+GPMC has certain timings that has to be programmed for proper
+functioning of the peripheral, while peripheral has another set of
+timings. To have peripheral work with gpmc, peripheral timings has to
+be translated to the form gpmc can understand. The way it has to be
+translated depends on the connected peripheral. Also there is a
+dependency for certain gpmc timings on gpmc clock frequency. Hence a
+generic timing routine was developed to achieve above requirements.
+
+Generic routine provides a generic method to calculate gpmc timings
+from gpmc peripheral timings. struct gpmc_device_timings fields has to
+be updated with timings from the datasheet of the peripheral that is
+connected to gpmc. A few of the peripheral timings can be fed either
+in time or in cycles, provision to handle this scenario has been
+provided (refer struct gpmc_device_timings definition). It may so
+happen that timing as specified by peripheral datasheet is not present
+in timing structure, in this scenario, try to correlate peripheral
+timing to the one available. If that doesn't work, try to add a new
+field as required by peripheral, educate generic timing routine to
+handle it, make sure that it does not break any of the existing.
+Then there may be cases where peripheral datasheet doesn't mention
+certain fields of struct gpmc_device_timings, zero those entries.
+
+Generic timing routine has been verified to work properly on
+multiple onenand's and tusb6010 peripherals.
+
+A word of caution: generic timing routine has been developed based
+on understanding of gpmc timings, peripheral timings, available
+custom timing routines, a kind of reverse engineering without
+most of the datasheets & hardware (to be exact none of those supported
+in mainline having custom timing routine) and by simulation.
+
+gpmc timing dependency on peripheral timings:
+
+[<gpmc_timing>: <peripheral timing1>, <peripheral timing2> ...]
+
+1. common
+
+cs_on:
+	t_ceasu
+adv_on:
+	t_avdasu, t_ceavd
+
+2. sync common
+
+sync_clk:
+	clk
+page_burst_access:
+	t_bacc
+clk_activation:
+	t_ces, t_avds
+
+3. read async muxed
+
+adv_rd_off:
+	t_avdp_r
+oe_on:
+	t_oeasu, t_aavdh
+access:
+	t_iaa, t_oe, t_ce, t_aa
+rd_cycle:
+	t_rd_cycle, t_cez_r, t_oez
+
+4. read async non-muxed
+
+adv_rd_off:
+	t_avdp_r
+oe_on:
+	t_oeasu
+access:
+	t_iaa, t_oe, t_ce, t_aa
+rd_cycle:
+	t_rd_cycle, t_cez_r, t_oez
+
+5. read sync muxed
+
+adv_rd_off:
+	t_avdp_r, t_avdh
+oe_on:
+	t_oeasu, t_ach, cyc_aavdh_oe
+access:
+	t_iaa, cyc_iaa, cyc_oe
+rd_cycle:
+	t_cez_r, t_oez, t_ce_rdyz
+
+6. read sync non-muxed
+
+adv_rd_off:
+	t_avdp_r
+oe_on:
+	t_oeasu
+access:
+	t_iaa, cyc_iaa, cyc_oe
+rd_cycle:
+	t_cez_r, t_oez, t_ce_rdyz
+
+7. write async muxed
+
+adv_wr_off:
+	t_avdp_w
+we_on, wr_data_mux_bus:
+	t_weasu, t_aavdh, cyc_aavhd_we
+we_off:
+	t_wpl
+cs_wr_off:
+	t_wph
+wr_cycle:
+	t_cez_w, t_wr_cycle
+
+8. write async non-muxed
+
+adv_wr_off:
+	t_avdp_w
+we_on, wr_data_mux_bus:
+	t_weasu
+we_off:
+	t_wpl
+cs_wr_off:
+	t_wph
+wr_cycle:
+	t_cez_w, t_wr_cycle
+
+9. write sync muxed
+
+adv_wr_off:
+	t_avdp_w, t_avdh
+we_on, wr_data_mux_bus:
+	t_weasu, t_rdyo, t_aavdh, cyc_aavhd_we
+we_off:
+	t_wpl, cyc_wpl
+cs_wr_off:
+	t_wph
+wr_cycle:
+	t_cez_w, t_ce_rdyz
+
+10. write sync non-muxed
+
+adv_wr_off:
+	t_avdp_w
+we_on, wr_data_mux_bus:
+	t_weasu, t_rdyo
+we_off:
+	t_wpl, cyc_wpl
+cs_wr_off:
+	t_wph
+wr_cycle:
+	t_cez_w, t_ce_rdyz
+
+
+Note:
+  Many of gpmc timings are dependent on other gpmc timings (a few
+  gpmc timings purely dependent on other gpmc timings, a reason that
+  some of the gpmc timings are missing above), and it will result in
+  indirect dependency of peripheral timings to gpmc timings other than
+  mentioned above, refer timing routine for more details. To know what
+  these peripheral timings correspond to, please see explanations in
+  struct gpmc_device_timings definition. And for gpmc timings refer
+  IP details (link above).