staging: axis-fifo: add unspecified HAS_IOMEM dependency

Currently CONFIG_XIL_AXIS_FIFO=y implicitly depends on
CONFIG_HAS_IOMEM=y; consequently, on architectures without IOMEM we get
the following build error:

ld: drivers/staging/axis-fifo/axis-fifo.o: in function `axis_fifo_probe':
drivers/staging/axis-fifo/axis-fifo.c:809: undefined reference to `devm_ioremap_resource'

Fix the build error by adding the unspecified dependency.

Reported-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
Link: https://lore.kernel.org/r/20191211192742.95699-7-brendanhiggins@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

staging: remove redundant 'default n' from Kconfig

'default n' is the default value for any bool or tristate Kconfig
setting so there is no need to write it explicitly.

Also since commit f467c5640c29 ("kconfig: only write '# CONFIG_FOO
is not set' for visible symbols") the Kconfig behavior is the same
regardless of 'default n' being present or not:

...
One side effect of (and the main motivation for) this change is making
the following two definitions behave exactly the same:

config FOO
bool

config FOO
bool
default n

With this change, neither of these will generate a
'# CONFIG_FOO is not set' line (assuming FOO isn't selected/implied).
That might make it clearer to people that a bare 'default n' is
redundant.
...

Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

staging: axis-fifo: Add elaborate description in Kconfig

- The Xilinx AXI-Stream FIFO IP core driver description is elaborated.
- References: Xilinx PG080 document, axis-fifo.txt

Signed-off-by: Moses Christopher <moseschristopherb@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

staging: add missing SPDX lines to Kconfig files

There are a few remaining drivers/staging/*/Kconfig files that do not
have SPDX identifiers in them. Add the correct GPL-2.0 identifier to
them to make scanning tools happy.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

staging: axis-fifo: add CONFIG_OF dependency

When building without CONFIG_OF, the compiler loses track of the flow
control in axis_fifo_probe(), and thinks that many variables are used
without an initialization even though we actually leave the function
before the first use:

drivers/staging/axis-fifo/axis-fifo.c: In function 'axis_fifo_probe':
drivers/staging/axis-fifo/axis-fifo.c:900:5: error: 'rxd_tdata_width' may be used uninitialized in this function [-Werror=maybe-uninitialized]
if (rxd_tdata_width != 32) {
^
drivers/staging/axis-fifo/axis-fifo.c:907:5: error: 'txd_tdata_width' may be used uninitialized in this function [-Werror=maybe-uninitialized]
if (txd_tdata_width != 32) {
^
drivers/staging/axis-fifo/axis-fifo.c:914:5: error: 'has_tdest' may be used uninitialized in this function [-Werror=maybe-uninitialized]
if (has_tdest) {
^
drivers/staging/axis-fifo/axis-fifo.c:919:5: error: 'has_tid' may be used uninitialized in this function [-Werror=maybe-uninitialized]

When CONFIG_OF is set, this does not happen, and since the driver cannot
work without it, just add that option as a Kconfig dependency.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

staging: add driver for Xilinx AXI-Stream FIFO v4.1 IP core

This IP core has read and write AXI-Stream FIFOs, the contents of which can
be accessed from the AXI4 memory-mapped interface. This is useful for
transferring data from a processor into the FPGA fabric. The driver creates
a character device that can be read/written to with standard
open/read/write/close.

See Xilinx PG080 document for IP details.

https://www.xilinx.com/support/documentation/ip_documentation/axi_fifo_mm_s/v4_1/pg080-axi-fifo-mm-s.pdf

The driver currently supports only store-forward mode with a 32-bit
AXI4 Lite interface. DOES NOT support:
- cut-through mode
- AXI4 (non-lite)

Signed-off-by: Jacob Feder <jacobsfeder@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>