misc: sram: Improve and simplify clk handling

The current code tries to get an associated clk, ignores any errors in the
process and if there is a clock enables it unconditionally for the whole
lifetime of the sram device.

Instead use an "optional" variant of devm_clk_get() which handles the case
where no clk is needed for the sram device and do proper error handling
for the remaining error cases. Also use an "enabled" variant of
devm_clk_get() to simplify. With that .probe() is the only function using
struct sram_dev::clk, so it can be replaced by a local variable.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://lore.kernel.org/r/20230302091251.1852454-1-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

misc: sram: Only map reserved areas in Tegra SYSRAM

On Tegra186 and later, a portion of the SYSRAM may be reserved for use
by TZ. Non-TZ memory accesses to this portion, including speculative
accesses, trigger SErrors that bring down the system. This does also
happen in practice occasionally (due to speculative accesses).

To fix the issue, add a flag to the SRAM driver to only map the
device tree-specified reserved areas depending on a flag set
based on the compatibility string. This would not affect non-Tegra
systems that rely on the entire thing being memory mapped.

If 64K pages are being used, we cannot exactly map the 4K regions
that are placed in SYSRAM - ioremap code instead aligns to closest
64K pages. However, since in practice the non-accessible memory area
is 64K aligned, these mappings do not overlap with the non-accessible
memory area and things work out.

Reviewed-by: Mian Yousaf Kaukab <ykaukab@suse.de>
Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Link: https://lore.kernel.org/r/20210715103423.1811101-1-mperttunen@nvidia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500

Based on 2 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation #

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-only

has been chosen to replace the boilerplate/reference in 4122 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Enrico Weigelt <info@metux.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

misc: sram: Integrate protect-exec reserved sram area type

Introduce a new "protect-exec" reserved sram area type which is
makes use of the the existing functionality provided for the "pool"
sram region type for use with the genalloc framework and with the
added requirement that it be maintained as read-only and executable
while allowing for an arbitrary number of drivers to share the space.

This introduces a common way to maintain a region of sram as read-only
and executable and also introduces a helper function, sram_exec_copy,
which allows for copying data to this protected region while maintaining
locking to avoid conflicts between multiple users of the same space. A
region of memory that is marked with the "protect-exec" flag in the
device tree also has the requirement of providing a page aligned block
of memory so that the page attribute manipulation does not affect
surrounding regions.

Also, selectively enable this only for builds that support set_memory_*
calls, for now just ARM, through the use of Kconfig.

Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

misc: sram: Introduce support code for protect-exec sram type

Some platforms, like many ARM SoCs, require the ability to run code from
on-chip memory like SRAM for tasks like reconfiguring the SDRAM
controller or entering low-power sleep modes. In order to do this we
must be able to allocate memory that the code can be copied to but then
change the mapping to be read-only and executable so that no memory is
both writable and executable at the same time to avoid opening any
unneccesary security holes.

By using the existing "pool" partition type that the SRAM driver allows
we can create a memory space that will already be exposed by the
genalloc framework to allow for allocating memory but we must extend
this to meet the executable requirements. By making use of various
set_memory_* APIs we can change the attributes of pages to make them
writable for code upload but then read-only and executable when we want
to actually run code. Because SRAM is a shared resource we need a
centralized manager of these set memory calls. Because the SRAM driver
itself is responsible for allocating the memory we can introduce a
sram_copy_exec API for the driver that works like memcpy but also
manages the page attributes and locking to allow multiple users of the
same SRAM space to all copy their code over independent of other each
before starting execution.

It is maintained in a separate file from the core SRAM driver to allow
it to be selectively built depending on whether or not a platform has
the appropriate set_memory_* APIs. A future patch will integrate it with
the core SRAM driver.

Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

misc: sram: Split sram data structures into local header

In preparation of a coming file split of the sram driver, move the
common data structures into a local header file that can be shared
between files related to the sram driver.

Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>