ARM: AM33xx: PRM: Implement REBOOT_COLD

Historically AM33xx performed warm software reset even though requested
(and default) was REBOOT_COLD. Reflect the de-facto default mode in
/sys/kernel/reboot/mode correctly and implement the real REBOOT_COLD
(if configured explicitly).
Tested-by: Matthias Michel <matthias.michel@siemens.com>
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Message-ID: <20240221154614.3549951-2-alexander.sverdlin@siemens.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/am33xx-restart.c

@@ -18,7 +18,8 @@
  */
 void am33xx_restart(enum reboot_mode mode, const char *cmd)
 {
-	/* TODO: Handle mode and cmd if necessary */
+	/* TODO: Handle cmd if necessary */
+	prm_reboot_mode = mode;
 
 	omap_prm_reset_system();
 }

arch/arm/mach-omap2/board-generic.c

@@ -246,6 +246,12 @@ DT_MACHINE_START(AM33XX_DT, "Generic AM33XX (Flattened Device Tree)")
 	.init_time	= omap_init_time_of,
 	.dt_compat	= am33xx_boards_compat,
 	.restart	= am33xx_restart,
+	/*
+	 * Historically am33xx supported only REBOOT_WARM even though default
+	 * reboot_mode was REBOOT_COLD. Reflect legacy de-facto behaviour in
+	 * SYSFS.
+	 */
+	.reboot_mode	= REBOOT_WARM,
 MACHINE_END
 #endif
 

arch/arm/mach-omap2/prm-regbits-33xx.h

@@ -15,6 +15,7 @@
 #define AM33XX_GFX_MEM_STATEST_MASK			(0x3 << 4)
 #define AM33XX_GLOBAL_WARM_SW_RST_MASK			(1 << 1)
 #define AM33XX_RST_GLOBAL_WARM_SW_MASK			(1 << 0)
+#define AM33XX_RST_GLOBAL_COLD_SW_MASK			(1 << 1)
 #define AM33XX_PRUSS_MEM_ONSTATE_MASK			(0x3 << 5)
 #define AM33XX_PRUSS_MEM_RETSTATE_MASK			(1 << 7)
 #define AM33XX_PRUSS_MEM_STATEST_MASK			(0x3 << 23)

arch/arm/mach-omap2/prm.h

@@ -15,6 +15,7 @@
 # ifndef __ASSEMBLER__
 extern struct omap_domain_base prm_base;
 extern u16 prm_features;
+extern enum reboot_mode prm_reboot_mode;
 int omap_prcm_init(void);
 int omap2_prcm_base_init(void);
 # endif

arch/arm/mach-omap2/prm33xx.c

@@ -10,6 +10,7 @@
 #include <linux/errno.h>
 #include <linux/err.h>
 #include <linux/io.h>
+#include <linux/reboot.h>
 
 #include "powerdomain.h"
 #include "prm33xx.h"
@@ -318,10 +319,19 @@ static int am33xx_check_vcvp(void)
  *
  * Immediately reboots the device through warm reset.
  */
-static void am33xx_prm_global_warm_sw_reset(void)
+static void am33xx_prm_global_sw_reset(void)
 {
-	am33xx_prm_rmw_reg_bits(AM33XX_RST_GLOBAL_WARM_SW_MASK,
-				AM33XX_RST_GLOBAL_WARM_SW_MASK,
+	/*
+	 * Historically AM33xx performed warm reset for all requested reboot_mode.
+	 * Keep this behaviour unchanged for all except newly added REBOOT_COLD.
+	 */
+	u32 mask = AM33XX_RST_GLOBAL_WARM_SW_MASK;
+
+	if (prm_reboot_mode == REBOOT_COLD)
+		mask = AM33XX_RST_GLOBAL_COLD_SW_MASK;
+
+	am33xx_prm_rmw_reg_bits(mask,
+				mask,
 				AM33XX_PRM_DEVICE_MOD,
 				AM33XX_PRM_RSTCTRL_OFFSET);
 
@@ -382,7 +392,7 @@ static struct prm_ll_data am33xx_prm_ll_data = {
 	.assert_hardreset		= am33xx_prm_assert_hardreset,
 	.deassert_hardreset		= am33xx_prm_deassert_hardreset,
 	.is_hardreset_asserted		= am33xx_prm_is_hardreset_asserted,
-	.reset_system			= am33xx_prm_global_warm_sw_reset,
+	.reset_system			= am33xx_prm_global_sw_reset,
 };
 
 int __init am33xx_prm_init(const struct omap_prcm_init_data *data)

arch/arm/mach-omap2/prm_common.c

@@ -66,6 +66,12 @@ struct omap_domain_base prm_base;
 
 u16 prm_features;
 
+/*
+ * Platforms that implement different reboot modes can store the requested
+ * mode here.
+ */
+enum reboot_mode prm_reboot_mode;
+
 /*
  * prm_ll_data: function pointers to SoC-specific implementations of
  * common PRM functions