ELBERT: SCM fpga upgrade keeps x86 state (#95)

Summary:
ELBERT: SCM fpga upgrade keeps x86 state

Previously, SCM fpga upgrades would reset the x86 enable register to the default  which is x86 off. To prevent this, we need to latch and restore the x86 reset signal when programming scm fpga.

Testing:
Before this image: an upgrade would cause x86 to go down until reboot/powercycle
After this image: Downgrade/Upgraded and confirmed that x86 stays up. Repeated 30 times.

Pull Request resolved: facebookexternal/openbmc.arista#95

Reviewed By: benwei13

fbshipit-source-id: d69748af68

meta-facebook/meta-elbert/recipes-utils/openbmc-utils/files/fpga_util.sh

@@ -6,6 +6,7 @@
 
 CPLD_JTAG_SEL_L="CPLD_JTAG_SEL_L"
 JTAG_TRST_L="JTAG_TRST_L"
+SCM_FPGA_LATCH_L="SCM_FPGA_LATCH_L"
 JTAG_EN="${SCMCPLD_SYSFS_DIR}/jtag_en"
 PROGRAM_SEL="${SCMCPLD_SYSFS_DIR}/program_sel"
 SPI_CTRL="${SMBCPLD_SYSFS_DIR}/spi_ctrl"
@@ -16,6 +17,7 @@ SMB_SPIDEV="spidev1.1"
 
 SCM_PROGRAM=false
 SMB_PROGRAM=false
+CACHED_SCM_PWR_ON_SYSFS="0x1"
 
 trap disconnect_program_paths INT TERM QUIT EXIT
 
@@ -33,17 +35,31 @@ disconnect_program_paths() {
     # Return values to defaults
     gpio_set_value $CPLD_JTAG_SEL_L 1
     gpio_set_value $JTAG_TRST_L 0
-    if [ "$SCM_PROGRAM" = false ]; then
+    if [ "$SCM_PROGRAM" = true ]; then
+        # Give SCM cpld time to come back on SMBus
+        sleep 2
+        # Restore x86 power state
+        echo "$CACHED_SCM_PWR_ON_SYSFS" > "$SCM_PWR_ON_SYSFS" || {
+           echo "Failed to recover CPU power state."
+        }
+        sleep 1
+        gpio_set_value $SCM_FPGA_LATCH_L 1
+    else
         echo 0 > "$JTAG_EN"
         echo 1 > "$PROGRAM_SEL"
     fi
+
     if [ "$SMB_PROGRAM" = false ]; then
         echo 0 > "$SPI_CTRL"
         echo 0 > "$JTAG_CTRL"
     fi
 }
 
 connect_scm_jtag() {
+    # Store initial state of x86 power in order to restore after programming
+    CACHED_SCM_PWR_ON_SYSFS="$(head -n 1 "$SCM_PWR_ON_SYSFS" 2> /dev/null)"
+    gpio_set_value $SCM_FPGA_LATCH_L 0
+
     gpio_set_value $CPLD_JTAG_SEL_L 0
     gpio_set_value $JTAG_TRST_L 1
     echo 0 > "$JTAG_EN"

meta-facebook/meta-elbert/recipes-utils/openbmc-utils/files/setup_i2c.sh

@@ -91,6 +91,7 @@ i2c_device_add 7 0x50 24c512
 
 # SMBus 9 SCM DPM UCD90320
 hwmon_device_add 9 0x11 ucd90320
+gpio_export_by_offset 9-0011 13 SCM_FPGA_LATCH_L
 
 # SMBus 10 SCM POWER
 i2c_device_add 10 0x30 cpupwr