zynqmp: restore the jtag interface

When boot.bin is configured for secure boot the CSU will disable the
JTAG interface on all cases.

Some boards might rely on this interface for flashing to QSPI in which
case those systems might end up bricked during development.

This commit will restore the interface under CSU control

Signed-off-by: Jorge Ramirez-Ortiz <jorge@foundries.io>
Link: https://lore.kernel.org/r/20211013134800.19452-1-jorge@foundries.io
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/arm/mach-zynqmp/Kconfig

@@ -149,6 +149,14 @@ config SPL_ZYNQMP_ALT_BOOTMODE_ENABLED
 	  Overwrite bootmode selected via boot mode pins to tell SPL what should
 	  be the next boot device.
 
+config SPL_ZYNQMP_RESTORE_JTAG
+	bool "Restore JTAG"
+	depends on SPL
+	help
+	  Booting SPL in secure mode causes the CSU to disable the JTAG interface
+	  even if no eFuses were burnt. This option restores the interface if
+	  possible.
+
 config ZYNQ_SDHCI_MAX_FREQ
 	default 200000000
 

arch/arm/mach-zynqmp/include/mach/hardware.h

@@ -39,20 +39,26 @@
 #define RESET_REASON_INTERNAL	BIT(1)
 #define RESET_REASON_EXTERNAL	BIT(0)
 
+#define CRLAPB_DBG_LPD_CTRL_SETUP_CLK	0x01002002
+#define CRLAPB_RST_LPD_DBG_RESET	0
+
 struct crlapb_regs {
 	u32 reserved0[36];
 	u32 cpu_r5_ctrl; /* 0x90 */
-	u32 reserved1[37];
+	u32 reserved1[7];
+	u32 dbg_lpd_ctrl; /* 0xB0 */
+	u32 reserved2[29];
 	u32 timestamp_ref_ctrl; /* 0x128 */
-	u32 reserved2[53];
+	u32 reserved3[53];
 	u32 boot_mode; /* 0x200 */
-	u32 reserved3_0[7];
+	u32 reserved4_0[7];
 	u32 reset_reason; /* 0x220 */
-	u32 reserved3_1[6];
+	u32 reserved4_1[6];
 	u32 rst_lpd_top; /* 0x23C */
-	u32 reserved4[4];
+	u32 rst_lpd_dbg; /* 0x240 */
+	u32 reserved5[3];
 	u32 boot_pin_ctrl; /* 0x250 */
-	u32 reserved5[21];
+	u32 reserved6[21];
 };
 
 #define crlapb_base ((struct crlapb_regs *)ZYNQMP_CRL_APB_BASEADDR)
@@ -141,12 +147,23 @@ struct apu_regs {
 #define ZYNQMP_SILICON_VER_MASK		0xF
 #define ZYNQMP_SILICON_VER_SHIFT	0
 
+#define CSU_JTAG_SEC_GATE_DISABLE	GENMASK(7, 0)
+#define CSU_JTAG_DAP_ENABLE_DEBUG	GENMASK(7, 0)
+#define CSU_JTAG_CHAIN_WR_SETUP		GENMASK(1, 0)
+#define CSU_PCAP_PROG_RELEASE_PL	BIT(0)
+
 struct csu_regs {
 	u32 reserved0[4];
 	u32 multi_boot;
-	u32 reserved1[11];
+	u32 reserved1[7];
+	u32 jtag_chain_status_wr;
+	u32 jtag_chain_status;
+	u32 jtag_sec;
+	u32 jtag_dap_cfg;
 	u32 idcode;
 	u32 version;
+	u32 reserved2[3055];
+	u32 pcap_prog;
 };
 
 #define csu_base ((struct csu_regs *)ZYNQMP_CSU_BASEADDR)

board/xilinx/zynqmp/zynqmp.c

@@ -358,6 +358,21 @@ static int multi_boot(void)
 	return multiboot;
 }
 
+#if defined(CONFIG_SPL_BUILD)
+static void restore_jtag(void)
+{
+	if (current_el() != 3)
+		return;
+
+	writel(CSU_JTAG_SEC_GATE_DISABLE, &csu_base->jtag_sec);
+	writel(CSU_JTAG_DAP_ENABLE_DEBUG, &csu_base->jtag_dap_cfg);
+	writel(CSU_JTAG_CHAIN_WR_SETUP, &csu_base->jtag_chain_status_wr);
+	writel(CRLAPB_DBG_LPD_CTRL_SETUP_CLK, &crlapb_base->dbg_lpd_ctrl);
+	writel(CRLAPB_RST_LPD_DBG_RESET, &crlapb_base->rst_lpd_dbg);
+	writel(CSU_PCAP_PROG_RELEASE_PL, &csu_base->pcap_prog);
+}
+#endif
+
 #define PS_SYSMON_ANALOG_BUS_VAL	0x3210
 #define PS_SYSMON_ANALOG_BUS_REG	0xFFA50914
 
@@ -377,6 +392,10 @@ int board_init(void)
 		zynqmp_pmufw_load_config_object(zynqmp_pm_cfg_obj,
 						zynqmp_pm_cfg_obj_size);
 	printf("Silicon version:\t%d\n", zynqmp_get_silicon_version());
+
+	/* the CSU disables the JTAG interface when secure boot is enabled */
+	if (CONFIG_IS_ENABLED(SPL_ZYNQMP_RESTORE_JTAG))
+		restore_jtag();
 #else
 	if (CONFIG_IS_ENABLED(DM_I2C) && CONFIG_IS_ENABLED(I2C_EEPROM))
 		xilinx_read_eeprom();