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Disable PL310 outer cache sync for IO coherent platforms

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When a PL310 cache is used on a system that provides hardware
coherency, the outer cache sync operation is useless, and can be
skipped. Moreover, on some systems, it is harmful as it causes
deadlocks between the Marvell coherency mechanism, the Marvell PCIe
or Crypto controllers and the Cortex-A9.

To avoid this, this commit introduces a new Device Tree property
'arm,io-coherent' for the L2 cache controller node, valid only for the
PL310 cache. It identifies the usage of the PL310 cache in an I/O
coherent configuration. Internally, it makes the driver disable the
outer cache sync operation.

Note, that other outer-cache operations are not removed, as they may
be needed for certain situations, such as booting secondary CPUs.
Moreover, in order to enable IO coherent operation, the decision
whether to use L2 cache maintenance callbacks is done in busdma
layer, which was enabled in one of the previous commits.

Submitted by: Michal Mazur <mkm@semihalf.com>
	      Marcin Wojtas <mw@semihalf.com>
Reviewed by: mmel
Obtained from: Semihalf
Differential revision: https://reviews.freebsd.org/D11245
This commit is contained in:
Zbigniew Bodek 2017-06-20 11:11:42 +00:00
parent b50f666958
commit 8cbc8d3dd1
2 changed files with 15 additions and 0 deletions
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14
sys/arm/arm/pl310.c
View File

@ -206,6 +206,10 @@ pl310_cache_sync(void)
if ((pl310_softc == NULL) || !pl310_softc->sc_enabled)
return;
/* Do not sync outer cache on IO coherent platform */
if (pl310_softc->sc_io_coherent)
return;
#ifdef PL310_ERRATA_753970
if (pl310_softc->sc_rtl_revision == CACHE_ID_RELEASE_r3p0)
/* Write uncached PL310 register */
@ -444,6 +448,7 @@ pl310_attach(device_t dev)
struct pl310_softc *sc = device_get_softc(dev);
int rid;
uint32_t cache_id, debug_ctrl;
phandle_t node;
sc->sc_dev = dev;
rid = 0;
@ -470,6 +475,15 @@ pl310_attach(device_t dev)
(cache_id >> CACHE_ID_PARTNUM_SHIFT) & CACHE_ID_PARTNUM_MASK,
(cache_id >> CACHE_ID_RELEASE_SHIFT) & CACHE_ID_RELEASE_MASK);
/*
* Test for "arm,io-coherent" property and disable sync operation if
* platform is I/O coherent. Outer sync operations are not needed
* on coherent platform and may be harmful in certain situations.
*/
node = ofw_bus_get_node(dev);
if (OF_hasprop(node, "arm,io-coherent"))
sc->sc_io_coherent = true;
/*
* If L2 cache is already enabled then something has violated the rules,
* because caches are supposed to be off at kernel entry. The cache

1
sys/arm/include/pl310.h
View File

@ -148,6 +148,7 @@ struct pl310_softc {
struct mtx sc_mtx;
u_int sc_rtl_revision;
struct intr_config_hook *sc_ich;
boolean_t sc_io_coherent;
};
/**