hwrng: stm32 - repair clock handling

The clock management in this driver does not seem to be correct. The
struct hwrng .init callback enables the clock, but there is no matching
.cleanup callback to disable the clock. The clock get disabled as some
later point by runtime PM suspend callback.

Furthermore, both runtime PM and sleep suspend callbacks access registers
first and disable clock which are used for register access second. If the
IP is already in RPM suspend and the system enters sleep state, the sleep
callback will attempt to access registers while the register clock are
already disabled. This bug has been fixed once before already in commit
9bae54942b13 ("hwrng: stm32 - fix pm_suspend issue"), and regressed in
commit ff4e46104f2e ("hwrng: stm32 - rework power management sequences") .

Fix this slightly differently, disable register clock at the end of .init
callback, this way the IP is disabled after .init. On every access to the
IP, which really is only stm32_rng_read(), do pm_runtime_get_sync() which
is already done in stm32_rng_read() to bring the IP from RPM suspend, and
pm_runtime_mark_last_busy()/pm_runtime_put_sync_autosuspend() to put it
back into RPM suspend.

Change sleep suspend/resume callbacks to enable and disable register clock
around register access, as those cannot use the RPM suspend/resume callbacks
due to slightly different initialization in those sleep callbacks. This way,
the register access should always be performed with clock surely enabled.

Fixes: ff4e46104f2e ("hwrng: stm32 - rework power management sequences")
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - put IP into RPM suspend on failure

In case of an irrecoverable failure, put the IP into RPM suspend
to avoid RPM imbalance. I did not trigger this case, but it seems
it should be done based on reading the code.

Fixes: b17bc6eb7c2b ("hwrng: stm32 - rework error handling in stm32_rng_read()")
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - use logical OR in conditional

The conditional is used to check whether err is non-zero OR whether
reg variable is non-zero after clearing bits from it. This should be
done using logical OR, not bitwise OR, fix it.

Fixes: 6b85a7e141cb ("hwrng: stm32 - implement STM32MP13x support")
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - Convert to platform remove callback returning void

The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is ignored (apart
from emitting a warning) and this typically results in resource leaks.

To improve here there is a quest to make the remove callback return
void. In the first step of this quest all drivers are converted to
.remove_new(), which already returns void. Eventually after all drivers
are converted, .remove_new() will be renamed to .remove().

Trivially convert this driver from always returning zero in the remove
callback to the void returning variant.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - add missing clk_disable_unprepare() in stm32_rng_init()

Add clk_disable_unprepare() in the error path in stm32_rng_init().

Fixes: 6b85a7e141cb ("hwrng: stm32 - implement STM32MP13x support")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - rework power management sequences

Implement stm32_rng_suspend()/stm32_rng_resume() low-power APIs
called when the hardware block context will be lost.

There is no need to save the RNG_CR register in
stm32_rng_runtime_suspend() as the context is not lost. Therefore,
only enable/disable the RNG in the runtime sequences.

Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - support RNG configuration locking mechanism

If "st,rng-lock-conf" DT binding property is set for a stm32-rng node,
the RNG configuration will be locked until next hardware block reset
or platform reset.

Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - restrain RNG noise source clock

For NIST certification the noise source sampling may need to be
restrained.

This change implements an algorithm that gets the rate of the RNG
clock and apply the correct value in CLKDIV field in RNG_CR register
to force the RNG clock rate to be "max_clock_rate" maximum.

As it is platform-specific, implement it as a compat data.

Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - rework error handling in stm32_rng_read()

Try to conceal seed errors when possible. If, despite the error
concealing tries, a seed error is still present, then return an error.

A clock error does not compromise the hardware block and data can
still be read from RNG_DR. Just warn that the RNG clock is too slow
and clear RNG_SR.

Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - implement error concealment

The RNG driver should be capable of recovering from an error. Implement
an error concealment API. This avoids irrecoverable RNG state.

Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - implement STM32MP13x support

The RNG present on STM32MP13x platforms introduces a customizable
configuration and the conditional reset.

STM32 RNG configuration should best fit the requirements of the
platform. Therefore, put a platform-specific RNG configuration
field in the platform data. Default RNG configuration for STM32MP13
is the NIST certified configuration [1].

While there, fix and the RNG init sequence to support all RNG
versions.

[1] https://csrc.nist.gov/projects/cryptographic-module-validation-program/entropy-validations/certificate/53

Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - use devm_platform_get_and_ioremap_resource() API

Use devm_platform_get_and_ioremap_resource() to get and ioremap a
resource.

Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: Explicitly include correct DT includes

The DT of_device.h and of_platform.h date back to the separate
of_platform_bus_type before it was merged into the regular platform bus.
As part of that merge prepping Arm DT support 13 years ago, they
"temporarily" include each other. They also include platform_device.h
and of.h. As a result, there's a pretty much random mix of those include
files used throughout the tree. In order to detangle these headers and
replace the implicit includes with struct declarations, users need to
explicitly include the correct includes.

Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - rename readl return value

Use a more meaningful name for the readl return value variable.

Link: https://lore.kernel.org/all/Y1J3QwynPFIlfrIv@loth.rohan.me.apana.org.au/

Signed-off-by: Tomas Marek <tomas.marek@elrest.cz>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - fix read of the last word

The stm32_rng_read() function samples TRNG by 4 bytes until at
least 5 bytes are free in the input buffer. The last four bytes
are never read. For example, 60 bytes are returned in case the
input buffer size is 64 bytes.

Read until at least 4 bytes are free in the input buffer. Fill
the buffer entirely in case the buffer size is divisible by 4.

Cc: Oleg Karfich <oleg.karfich@wago.com>
Signed-off-by: Tomas Marek <tomas.marek@elrest.cz>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - fix number of returned bytes on read

The stm32_rng_read() function uses `retval` variable as a counter of
generated random bytes. However, the same variable is used to store
a result of the polling function in case the driver is waiting until
the TRNG is ready. The TRNG generates random numbers by 16B. One
loop read 4B. So, the function calls the polling every 16B, i.e.
every 4th loop. The `retval` counter is reset on poll call and only
number of bytes read after the last poll call is returned to the
caller. The remaining sampled random bytes (for example 48 out of
64 in case 64 bytes are read) are not used.

Use different variable to store the polling function result and
do not overwrite `retval` counter.

Cc: Oleg Karfich <oleg.karfich@wago.com>
Signed-off-by: Tomas Marek <tomas.marek@elrest.cz>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - use semicolons rather than commas to separate statements

Replace commas with semicolons. What is done is essentially described by
the following Coccinelle semantic patch (http://coccinelle.lip6.fr/):

// <smpl>
@@ expression e1,e2; @@
e1
-,
+;
e2
... when any
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 110

Based on 1 normalized pattern(s):

this file is free software you can redistribute it and or modify it
under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version this file is distributed in the hope
that it will be useful but without any warranty without even the
implied warranty of merchantability or fitness for a particular
purpose see the gnu general public license for more details

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 1 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190523091650.284757242@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

hwrng: stm32 - set default random quality

Add a default quality to hw_random device to be
automatically set as new default entropy. Setting
random quality will decrease the crng init time by
switching to this hardware random source.

Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - fix unbalanced pm_runtime_enable

No remove function implemented yet in the driver.
Without remove function, the pm_runtime implementation
complains when removing and probing again the driver.

Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - fix pm_suspend issue

When suspend is called after pm_runtime_suspend,
same callback is used and access to rng register is
freezing system. By calling the pm_runtime_force_suspend,
it first checks that runtime has been already done.

Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - rework read timeout calculation

Increase timeout delay to support longer timing linked
to rng initialization. Measurement is based on timer instead
of instructions per iteration which is not powerful on all
targets.

Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - allow disable clock error detection

Add a new property that allow to disable the clock error
detection which is required when the clock source selected
is out of specification (which is not mandatory).

Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - add reset during probe

Avoid issue when probing the RNG without
reset if bad status has been detected previously

Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - fix maybe uninitialized variable warning

This patch fixes the following warning:
drivers/char/hw_random/stm32-rng.c: In function 'stm32_rng_read':
drivers/char/hw_random/stm32-rng.c:82:19: warning: 'sr' may be used
uninitialized in this function

Reported-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - Fix build with CONFIG_PM

Commit c6a97c42e399 ("hwrng: stm32 - add support for STM32 HW RNG")
was inadequately tested (actually it was tested quite hard so
incompetent would be a better description that inadequate) and does
not compile on platforms with CONFIG_PM set.

Fix this.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

hwrng: stm32 - add support for STM32 HW RNG

Add support for STMicroelectronics STM32 random number generator.

The config value defaults to N, reflecting the fact that STM32 is a
very low resource microcontroller platform and unlikely to be targeted
by any "grown up" defconfigs.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>