[PATCH] zynqmp: restore the jtag interface

[Jorge Ramirez-Ortiz]

As a security feature, if boot.bin was 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 attempts to restore the interface - if the CSU allows for it.

Signed-off-by: Jorge Ramirez-Ortiz <jorge at foundries.io>
---
 arch/arm/mach-zynqmp/Kconfig                 |  9 ++++++++
 arch/arm/mach-zynqmp/include/mach/hardware.h | 23 +++++++++++++------
 board/xilinx/zynqmp/zynqmp.c                 | 24 ++++++++++++++++++++
 3 files changed, 49 insertions(+), 7 deletions(-)

diff --git a/arch/arm/mach-zynqmp/Kconfig b/arch/arm/mach-zynqmp/Kconfig
index 39144d654e..1e551c0020 100644
--- a/arch/arm/mach-zynqmp/Kconfig
+++ b/arch/arm/mach-zynqmp/Kconfig
@@ -149,6 +149,15 @@ 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
+       default n
+       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
 
diff --git a/arch/arm/mach-zynqmp/include/mach/hardware.h b/arch/arm/mach-zynqmp/include/mach/hardware.h
index 3776499070..58822e3f25 100644
--- a/arch/arm/mach-zynqmp/include/mach/hardware.h
+++ b/arch/arm/mach-zynqmp/include/mach/hardware.h
@@ -42,17 +42,20 @@
 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)
@@ -141,9 +144,15 @@ struct apu_regs {
 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)
diff --git a/board/xilinx/zynqmp/zynqmp.c b/board/xilinx/zynqmp/zynqmp.c
index 1748fec2e4..feffda54e7 100644
--- a/board/xilinx/zynqmp/zynqmp.c
+++ b/board/xilinx/zynqmp/zynqmp.c
@@ -355,6 +355,25 @@ static int multi_boot(void)
 	return 0;
 }
 
+#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_ZYNQMP_RESTORE_JTAG)
+static void restore_jtag(void)
+{
+	const u32 disable_security_gate = 0xff;
+	const u32 setup_clock = 0x01002002;
+	const u32 setup_jtag = 0x3;
+	const u32 release_pl = 0x1;
+	const u32 enable_debug = 0xff;
+	const u32 do_reset = 0x0;
+
+	writel(disable_security_gate, &csu_base->jtag_sec);
+	writel(enable_debug, &csu_base->jtag_dap_cfg);
+	writel(setup_jtag, &csu_base->jtag_chain_status_wr);
+	writel(setup_clock, &crlapb_base->dbg_lpd_ctrl);
+	writel(do_reset, &crlapb_base->rst_lpd_dbg);
+	writel(release_pl, &csu_base->pcap_prog);
+}
+#endif
+
 #define PS_SYSMON_ANALOG_BUS_VAL	0x3210
 #define PS_SYSMON_ANALOG_BUS_REG	0xFFA50914
 
@@ -374,6 +393,11 @@ 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());
+
+#if defined(CONFIG_SPL_ZYNQMP_RESTORE_JTAG)
+	/* the CSU disables the JTAG interface when secure boot is enabled */
+	restore_jtag();
+#endif
 #else
 	if (CONFIG_IS_ENABLED(DM_I2C) && CONFIG_IS_ENABLED(I2C_EEPROM))
 		xilinx_read_eeprom();
-- 
2.31.1