linux-kernel - [PATCH 2/2] ARM: OMAP4: Store reboot mode to SAR scratchpad memory before restart

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Date:	Tue, 29 Mar 2016 21:25:17 +0200
From:	Paul Kocialkowski <contact@...lk.fr>
To:	linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	Tony Lindgren <tony@...mide.com>,
	Paul Kocialkowski <contact@...lk.fr>
Subject: [PATCH 2/2] ARM: OMAP4: Store reboot mode to SAR scratchpad memory before restart

This adds support for storing the reboot mode command to SAR scratchpad memory,
at a location compatible with TI kernels, so that bootloaders can grab the
reboot mode and act upon it.

Currently, upstream U-Boot has support for this feature on OMAP4.

Signed-off-by: Paul Kocialkowski <contact@...lk.fr>
---
 arch/arm/mach-omap2/common.h           |  1 +
 arch/arm/mach-omap2/omap4-common.c     | 12 ++++++++++++
 arch/arm/mach-omap2/omap4-restart.c    |  2 +-
 arch/arm/mach-omap2/omap4-sar-layout.h |  3 +++
 4 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mach-omap2/common.h b/arch/arm/mach-omap2/common.h
index f7666b9..d773385 100644
--- a/arch/arm/mach-omap2/common.h
+++ b/arch/arm/mach-omap2/common.h
@@ -258,6 +258,7 @@ extern bool gic_dist_disabled(void);
 extern void gic_timer_retrigger(void);
 extern void omap_smc1(u32 fn, u32 arg);
 extern void __iomem *omap4_get_sar_ram_base(void);
+extern void omap4_sar_ram_write_boot_mode(const char *cmd);
 extern void omap_do_wfi(void);
 
 #ifdef CONFIG_SMP
diff --git a/arch/arm/mach-omap2/omap4-common.c b/arch/arm/mach-omap2/omap4-common.c
index 949696b..85f251e 100644
--- a/arch/arm/mach-omap2/omap4-common.c
+++ b/arch/arm/mach-omap2/omap4-common.c
@@ -265,6 +265,18 @@ void __iomem *omap4_get_sar_ram_base(void)
 	return sar_ram_base;
 }
 
+void omap4_sar_ram_write_boot_mode(const char *cmd)
+{
+	void __iomem *sar_base;
+
+	sar_base = omap4_get_sar_ram_base();
+
+	if (!cmd)
+		strncpy(sar_base + BOOT_MODE_OFFSET, "", BOOT_MODE_SIZE);
+	else
+		strncpy(sar_base + BOOT_MODE_OFFSET, cmd, BOOT_MODE_SIZE);
+}
+
 /*
  * SAR RAM used to save and restore the HW
  * context in low power modes
diff --git a/arch/arm/mach-omap2/omap4-restart.c b/arch/arm/mach-omap2/omap4-restart.c
index e17136a..74f29b5 100644
--- a/arch/arm/mach-omap2/omap4-restart.c
+++ b/arch/arm/mach-omap2/omap4-restart.c
@@ -22,6 +22,6 @@
  */
 void omap44xx_restart(enum reboot_mode mode, const char *cmd)
 {
-	/* XXX Should save 'cmd' into scratchpad for use after reboot */
+	omap4_sar_ram_write_boot_mode(cmd);
 	omap_prm_reset_system();
 }
diff --git a/arch/arm/mach-omap2/omap4-sar-layout.h b/arch/arm/mach-omap2/omap4-sar-layout.h
index 792b106..247b2bf 100644
--- a/arch/arm/mach-omap2/omap4-sar-layout.h
+++ b/arch/arm/mach-omap2/omap4-sar-layout.h
@@ -20,6 +20,7 @@
 #define SAR_BANK4_OFFSET		0x3000
 
 /* Scratch pad memory offsets from SAR_BANK1 */
+#define BOOT_MODE_OFFSET			0xa0c
 #define SCU_OFFSET0				0xfe4
 #define SCU_OFFSET1				0xfe8
 #define OMAP_TYPE_OFFSET			0xfec
@@ -28,6 +29,8 @@
 #define L2X0_AUXCTRL_OFFSET			0xff8
 #define L2X0_PREFETCH_CTRL_OFFSET		0xffc
 
+#define BOOT_MODE_SIZE				0xf
+
 /* CPUx Wakeup Non-Secure Physical Address offsets in SAR_BANK3 */
 #define CPU0_WAKEUP_NS_PA_ADDR_OFFSET		0xa04
 #define CPU1_WAKEUP_NS_PA_ADDR_OFFSET		0xa08
-- 
2.7.4