tree fcedd3b245b39c8e22412cc432c82ff3dc83c046
parent 8018d94caa14341beb44173664791163fb6c6a69
author Andre Przywara <andre.przywara@arm.com> 1680623545 +0100
committer Andre Przywara <andre.przywara@arm.com> 1680625240 +0100

fix(imx8mq): fix compilation with gcc >= 12.x

Starting with GCC >= 12.x the -Wall option includes -Werror=array-bounds
checks. Per default GCC treats all memory accesses below 4096 as NULL,
so access to ROMAPI causes the following warning:

------------
In file included from plat/imx/imx8m/imx8mq/imx8mq_bl31_setup.c:20:
In function 'mmio_read_8',
    inlined from 'imx8mq_soc_info_init' at plat/imx/imx8m/imx8mq/imx8mq_bl31_setup.c:70:16,
    inlined from 'bl31_platform_setup' at plat/imx/imx8m/imx8mq/imx8mq_bl31_setup.c:206:2:
include/lib/mmio.h:19:16: error: array subscript 0 is outside array bounds of 'volatile uint8_t[0]' {aka 'volatile unsigned char[]'} [-Werror=array-bounds]
   19 |         return *(volatile uint8_t*)addr;
      |                ^~~~~~~~~~~~~~~~~~~~~~~~
In function 'mmio_read_8',
    inlined from 'imx8mq_soc_info_init' at plat/imx/imx8m/imx8mq/imx8mq_bl31_setup.c:74:16,
    inlined from 'bl31_platform_setup' at plat/imx/imx8m/imx8mq/imx8mq_bl31_setup.c:206:2:
include/lib/mmio.h:19:16: error: array subscript 0 is outside array bounds of 'volatile uint8_t[0]' {aka 'volatile unsigned char[]'} [-Werror=array-bounds]
   19 |         return *(volatile uint8_t*)addr;
      |                ^~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
------------

This comes arguably from us somewhat abusing pointers to access MMIO
memory regions, which is not really covered by the C language.

Replace the pointer-dereferencing mmio_read_8() with an implementation
that uses inline assembly, to directly generate an 8-bit load
instruction. This avoids the compiler thinking that this access is using
a pointer it needs to jealously look after.

Change-Id: Iab39f6f615d51d3e8a1c54a1262d1e6ec208811d
Reported-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>