Without the volatile attribute, compilers are entitled to optimize out
the same asm(). In the case of __udelay() in syscounter.c, it calls
`get_ticks()` twice, one for the starting time and the second in the
loop to check the current time. When compilers inline `get_ticks()`
they see the same `mrrc` instructions and optimize out the second one.
This leads to infinite loop since we don't get updated value from the
system counter.
Here is a portion of the disassembly of __udelay:
88: 428b cmp r3, r1
8a: f8ce 20a4 str.w r2, [lr, #164] ; 0xa4
8e: bf08 it eq
90: 4282 cmpeq r2, r0
92: f8ce 30a0 str.w r3, [lr, #160] ; 0xa0
96: d3f7 bcc.n 88 <__udelay+0x88>
98: e8bd 8cf0 ldmia.w sp!, {r4, r5, r6, r7, sl, fp, pc}
Note that final jump / loop at 96 to 88, we don't have any `mrrc`.
With a volatile attribute, the above changes to this:
8a: ec53 2f0e mrrc 15, 0, r2, r3, cr14
8e: 42ab cmp r3, r5
90: f8c1 20a4 str.w r2, [r1, #164] ; 0xa4
94: bf08 it eq
96: 42a2 cmpeq r2, r4
98: f8c1 30a0 str.w r3, [r1, #160] ; 0xa0
9c: d3f5 bcc.n 8a <__udelay+0x8a>
9e: e8bd 8cf0 ldmia.w sp!, {r4, r5, r6, r7, sl, fp, pc}
a2: bf00 nop
I'm advised[1] to put volatile on all asm(), so this commit also adds it
to the asm() in timer_init().
[1]: https://lists.denx.de/pipermail/u-boot/2018-March/322062.html
Signed-off-by: Yasushi SHOJI <yasushi.shoji@gmail.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Change is consistent with other SOCs and it is in preparation
for adding SOMs. SOC's related files are moved from cpu/ to
mach-imx/<SOC>.
This change is also coherent with the structure in kernel.
Signed-off-by: Stefano Babic <sbabic@denx.de>
CC: Fabio Estevam <fabio.estevam@nxp.com>
CC: Akshay Bhat <akshaybhat@timesys.com>
CC: Ken Lin <Ken.Lin@advantech.com.tw>
CC: Marek Vasut <marek.vasut@gmail.com>
CC: Heiko Schocher <hs@denx.de>
CC: "Sébastien Szymanski" <sebastien.szymanski@armadeus.com>
CC: Christian Gmeiner <christian.gmeiner@gmail.com>
CC: Stefan Roese <sr@denx.de>
CC: Patrick Bruenn <p.bruenn@beckhoff.com>
CC: Troy Kisky <troy.kisky@boundarydevices.com>
CC: Nikita Kiryanov <nikita@compulab.co.il>
CC: Otavio Salvador <otavio@ossystems.com.br>
CC: "Eric Bénard" <eric@eukrea.com>
CC: Jagan Teki <jagan@amarulasolutions.com>
CC: Ye Li <ye.li@nxp.com>
CC: Peng Fan <peng.fan@nxp.com>
CC: Adrian Alonso <adrian.alonso@nxp.com>
CC: Alison Wang <b18965@freescale.com>
CC: Tim Harvey <tharvey@gateworks.com>
CC: Martin Donnelly <martin.donnelly@ge.com>
CC: Marcin Niestroj <m.niestroj@grinn-global.com>
CC: Lukasz Majewski <lukma@denx.de>
CC: Adam Ford <aford173@gmail.com>
CC: "Albert ARIBAUD (3ADEV)" <albert.aribaud@3adev.fr>
CC: Boris Brezillon <boris.brezillon@free-electrons.com>
CC: Soeren Moch <smoch@web.de>
CC: Richard Hu <richard.hu@technexion.com>
CC: Wig Cheng <wig.cheng@technexion.com>
CC: Vanessa Maegima <vanessa.maegima@nxp.com>
CC: Max Krummenacher <max.krummenacher@toradex.com>
CC: Stefan Agner <stefan.agner@toradex.com>
CC: Markus Niebel <Markus.Niebel@tq-group.com>
CC: Breno Lima <breno.lima@nxp.com>
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CC: "Łukasz Majewski" <l.majewski@samsung.com>
CC: Patrice Chotard <patrice.chotard@st.com>
CC: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
CC: Hans de Goede <hdegoede@redhat.com>
CC: Masahiro Yamada <yamada.masahiro@socionext.com>
CC: Stephen Warren <swarren@nvidia.com>
CC: Andre Przywara <andre.przywara@arm.com>
CC: "Álvaro Fernández Rojas" <noltari@gmail.com>
CC: York Sun <york.sun@nxp.com>
CC: Xiaoliang Yang <xiaoliang.yang@nxp.com>
CC: Chen-Yu Tsai <wens@csie.org>
CC: George McCollister <george.mccollister@gmail.com>
CC: Sven Ebenfeld <sven.ebenfeld@gmail.com>
CC: Filip Brozovic <fbrozovic@gmail.com>
CC: Petr Kulhavy <brain@jikos.cz>
CC: Eric Nelson <eric@nelint.com>
CC: Bai Ping <ping.bai@nxp.com>
CC: Anson Huang <Anson.Huang@nxp.com>
CC: Sanchayan Maity <maitysanchayan@gmail.com>
CC: Lokesh Vutla <lokeshvutla@ti.com>
CC: Patrick Delaunay <patrick.delaunay@st.com>
CC: Gary Bisson <gary.bisson@boundarydevices.com>
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CC: u-boot@lists.denx.de
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
