Merge pull request #59 from athoelke/review-barriers-v2

Correct usage of data and instruction barriers v2

3 files changed, 29 insertions, 1 deletions

diff --git a/plat/fvp/aarch64/plat_common.c b/plat/fvp/aarch64/plat_common.c
index c8e529d..e2f2343 100644
--- a/plat/fvp/aarch64/plat_common.c
+++ b/plat/fvp/aarch64/plat_common.c
@@ -69,6 +69,8 @@ void enable_mmu()
 	ttbr = (unsigned long) l1_xlation_table;
 
 	if (GET_EL(current_el) == MODE_EL3) {
+		assert((read_sctlr_el3() & SCTLR_M_BIT) == 0);
+
 		write_mair_el3(mair);
 		tcr |= TCR_EL3_RES1;
 		/* Invalidate EL3 TLBs */
@@ -77,11 +79,19 @@ void enable_mmu()
 		write_tcr_el3(tcr);
 		write_ttbr0_el3(ttbr);
 
+		/* ensure all translation table writes have drained into memory,
+		 * the TLB invalidation is complete, and translation register
+		 * writes are committed before enabling the MMU
+		 */
+		dsb();
+		isb();
+
 		sctlr = read_sctlr_el3();
 		sctlr |= SCTLR_WXN_BIT | SCTLR_M_BIT | SCTLR_I_BIT;
 		sctlr |= SCTLR_A_BIT | SCTLR_C_BIT;
 		write_sctlr_el3(sctlr);
 	} else {
+		assert((read_sctlr_el1() & SCTLR_M_BIT) == 0);
 
 		write_mair_el1(mair);
 		/* Invalidate EL1 TLBs */
@@ -90,11 +100,20 @@ void enable_mmu()
 		write_tcr_el1(tcr);
 		write_ttbr0_el1(ttbr);
 
+		/* ensure all translation table writes have drained into memory,
+		 * the TLB invalidation is complete, and translation register
+		 * writes are committed before enabling the MMU
+		 */
+		dsb();
+		isb();
+
 		sctlr = read_sctlr_el1();
 		sctlr |= SCTLR_WXN_BIT | SCTLR_M_BIT | SCTLR_I_BIT;
 		sctlr |= SCTLR_A_BIT | SCTLR_C_BIT;
 		write_sctlr_el1(sctlr);
 	}
+	/* ensure the MMU enable takes effect immediately */
+	isb();
 
 	return;
 }
@@ -113,6 +132,8 @@ void disable_mmu(void)
 		sctlr = sctlr & ~(SCTLR_M_BIT | SCTLR_C_BIT);
 		write_sctlr_el1(sctlr);
 	}
+	/* ensure the MMU disable takes effect immediately */
+	isb();
 
 	/* Flush the caches */
 	dcsw_op_all(DCCISW);
diff --git a/plat/fvp/plat_gic.c b/plat/fvp/plat_gic.c
index 8457af1..db3c9cf 100644
--- a/plat/fvp/plat_gic.c
+++ b/plat/fvp/plat_gic.c
@@ -86,6 +86,7 @@ void gicv3_cpuif_setup(void)
 	 */
 	scr_val = read_scr();
 	write_scr(scr_val | SCR_NS_BIT);
+	isb();	/* ensure NS=1 takes effect before accessing ICC_SRE_EL2 */
 
 	/*
 	 * By default EL2 and NS-EL1 software should be able to enable GICv3
@@ -103,9 +104,11 @@ void gicv3_cpuif_setup(void)
 	write_icc_sre_el2(val | ICC_SRE_EN | ICC_SRE_SRE);
 
 	write_icc_pmr_el1(GIC_PRI_MASK);
+	isb();	/* commite ICC_* changes before setting NS=0 */
 
 	/* Restore SCR_EL3 */
 	write_scr(scr_val);
+	isb();	/* ensure NS=0 takes effect immediately */
 }
 
 /*******************************************************************************
diff --git a/plat/fvp/plat_pm.c b/plat/fvp/plat_pm.c
index 5430fff..f80e2d7 100644
--- a/plat/fvp/plat_pm.c
+++ b/plat/fvp/plat_pm.c
@@ -54,7 +54,11 @@ int fvp_affinst_standby(unsigned int power_state)
 	if (target_afflvl != MPIDR_AFFLVL0)
 		return PSCI_E_INVALID_PARAMS;
 
-	/* Enter standby state */
+	/*
+	 * Enter standby state
+	 * dsb is good practice before using wfi to enter low power states
+	 */
+	dsb();
 	wfi();
 
 	return PSCI_E_SUCCESS;