[U-Boot] [PATCH V2 2/4] ARM: tegra: translate __asm_flush_l3_cache to assembly

[Stephen Warren]

From: Stephen Warren <swarren at nvidia.com>

When performing a cache disable function, code must not access DRAM.
That is because when the cache is disabled, it will be bypassed and all
loads and stores will be serviced by RAM. This prevents accessing any
dirty data in the cache. In turn, this means the stack cannot be
used, since that is in RAM. To guarantee that code doesn't use RAM (and
in particular the stack) __asm_flush_l3_cache() must be manually
implemented in assembly, rather than implemented in C since the compiler
won't know not to touch RAM.

Signed-off-by: Stephen Warren <swarren at nvidia.com>
---
v2: New patch.
---
 arch/arm/mach-tegra/tegra186/cache.S | 25 +++++++++++++++++++++++++
 arch/arm/mach-tegra/tegra186/cache.c | 23 -----------------------
 2 files changed, 25 insertions(+), 23 deletions(-)
 create mode 100644 arch/arm/mach-tegra/tegra186/cache.S
 delete mode 100644 arch/arm/mach-tegra/tegra186/cache.c

diff --git a/arch/arm/mach-tegra/tegra186/cache.S b/arch/arm/mach-tegra/tegra186/cache.S
new file mode 100644
index 000000000000..d876cd93b432
--- /dev/null
+++ b/arch/arm/mach-tegra/tegra186/cache.S
@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2016, NVIDIA CORPORATION.
+ *
+ * SPDX-License-Identifier: GPL-2.0
+ */
+
+#include <config.h>
+#include <linux/linkage.h>
+
+#define SMC_SIP_INVOKE_MCE		0x82FFFF00
+#define MCE_SMC_ROC_FLUSH_CACHE		(SMC_SIP_INVOKE_MCE | 11)
+
+ENTRY(__asm_flush_l3_cache)
+	mov	x0, #(MCE_SMC_ROC_FLUSH_CACHE & 0xffff)
+	movk	x0, #(MCE_SMC_ROC_FLUSH_CACHE >> 16), lsl #16
+	mov	x1, #0
+	mov	x2, #0
+	mov	x3, #0
+	mov	x4, #0
+	mov	x5, #0
+	mov	x6, #0
+	smc	#0
+	mov	x0, #0
+	ret
+ENDPROC(__asm_flush_l3_cache)
diff --git a/arch/arm/mach-tegra/tegra186/cache.c b/arch/arm/mach-tegra/tegra186/cache.c
deleted file mode 100644
index adaed8968eb9..000000000000
--- a/arch/arm/mach-tegra/tegra186/cache.c
+++ /dev/null
@@ -1,23 +0,0 @@
-/*
- * Copyright (c) 2016, NVIDIA CORPORATION.
- *
- * SPDX-License-Identifier: GPL-2.0
- */
-
-#include <common.h>
-#include <asm/system.h>
-
-#define SMC_SIP_INVOKE_MCE	0x82FFFF00
-#define MCE_SMC_ROC_FLUSH_CACHE	11
-
-int __asm_flush_l3_cache(void)
-{
-	struct pt_regs regs = {0};
-
-	isb();
-
-	regs.regs[0] = SMC_SIP_INVOKE_MCE | MCE_SMC_ROC_FLUSH_CACHE;
-	smc_call(&regs);
-
-	return 0;
-}
-- 
2.10.1