[U-Boot] [PATCH v4 03/10] Exynos542x: Add workaround for ARM errata 798870

[Nishanth Menon]

On 17:13-20150224, Nishanth Menon wrote:
> On 13:27-20150220, Akshay Saraswat wrote:
> > This patch adds workaround for ARM errata 798870 which says
> > "If back-to-back speculative cache line fills (fill A and fill B) are
> > issued from the L1 data cache of a CPU to the L2 cache, the second
> > request (fill B) is then cancelled, and the second request would have
> > detected a hazard against a recent write or eviction (write B) to the
> > same cache line as fill B then the L2 logic might deadlock."
> > 
> > Signed-off-by: Kimoon Kim <kimoon.kim at samsung.com>
> > Signed-off-by: Akshay Saraswat <akshay.s at samsung.com>
> > Reviewed-by: Simon Glass <sjg at chromium.org>
> > Tested-by: Simon Glass <sjg at chromium.org>
> > ---
> > Changes since v3:
> > 	- Added errata number in comment.
> > 	- Moved changes to arm generic armv7.h
> > 
> > Changes since v2:
> > 	- No change.
> > 
> > Changes since v1:
> > 	- Added Reviewed-by & Tested-by.
> > 	- Added space before */ on line # 40.
> > 
> >  arch/arm/include/asm/armv7.h | 16 ++++++++++++++++
> >  1 file changed, 16 insertions(+)
> > 
> > diff --git a/arch/arm/include/asm/armv7.h b/arch/arm/include/asm/armv7.h
> > index a13da23..a2040b7 100644
> > --- a/arch/arm/include/asm/armv7.h
> > +++ b/arch/arm/include/asm/armv7.h
> > @@ -69,6 +69,22 @@
> >  #define CP15DSB	asm volatile ("mcr     p15, 0, %0, c7, c10, 4" : : "r" (0))
> >  #define CP15DMB	asm volatile ("mcr     p15, 0, %0, c7, c10, 5" : : "r" (0))
> >  
> > +/*
> > + * Workaround for ARM errata # 798870
> > + * Set L2ACTLR[7] to reissue any memory transaction in the L2 that has been
> > + * stalled for 1024 cycles to verify that its hazard condition still exists.
> > + */
> > +static inline void v7_enable_l2_hazard_detect(void)
> > +{
> > +	uint32_t val;
> > +
> > +	/* L2ACTLR[7]: Enable hazard detect timeout */
> > +	asm volatile ("mrc     p15, 1, %0, c15, c0, 0\n\t" : "=r"(val));
> > +	val |= (1 << 7);
> > +	asm volatile ("mcr     p15, 1, %0, c15, c0, 0\n\t" : : "r"(val));
> 
> This wont work for us in DRA7/OMAP5 L2ACTLR cannot be modified by
> u-boot. has to go to secure world using smc call.
> 
> > +}
> > +
> > +void v7_en_l2_hazard_detect(void);
> >  void v7_outer_cache_enable(void);
> >  void v7_outer_cache_disable(void);
> >  void v7_outer_cache_flush_all(void);
> 
> How about this - using the series:
> https://patchwork.ozlabs.org/patch/443261/                
> https://patchwork.ozlabs.org/patch/443264/                
> https://patchwork.ozlabs.org/patch/443268/                
> https://patchwork.ozlabs.org/patch/443265/                
> https://patchwork.ozlabs.org/patch/443263/                
> https://patchwork.ozlabs.org/patch/443262/                
> https://patchwork.ozlabs.org/patch/443267/                
> https://patchwork.ozlabs.org/patch/443266/                
> https://patchwork.ozlabs.org/patch/443260/                

I think the following might work for exynos?

diff --git a/arch/arm/cpu/armv7/exynos/lowlevel_init.c b/arch/arm/cpu/armv7/exynos/lowlevel_init.c
index 83e1dcfc1e13..0157105524ca 100644
--- a/arch/arm/cpu/armv7/exynos/lowlevel_init.c
+++ b/arch/arm/cpu/armv7/exynos/lowlevel_init.c
@@ -42,6 +42,23 @@ enum {
 	DO_POWER	= 1 << 4,
 };
 
+#ifdef CONFIG_ARM_ARCH_CP15_ERRATA
+void arch_cp15_errata_workaround(u32 midr, u32 variant, u32 rev, u32 comb)
+{
+#ifdef CONFIG_ARM_ERRATA_798870
+	if (comb >= 0x20 && comb < 0x30) {
+		uint32_t l2actlr;
+
+		mrc_l2_aux_ctlr(l2actlr);
+		/* Disable ACE DVM/CMO message broadcas */
+		l2actlr |= (1 << 7);
+		mcr_l2_aux_ctlr(l2actlr);
+		mrc_l2_ctlr(l2actlr);
+	}
+#endif
+}
+#endif
+
 int do_lowlevel_init(void)
 {
 	uint32_t reset_status;
-- 
Regards,
Nishanth Menon