atsam: Enable chipid as usb serial number

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

docs/Config_Changes.md

@@ -6,9 +6,9 @@ All dates in this document are approximate.
 
 # Changes
 
-20191124: The USB names have changed on lpc176x, stm32, and atsamd.
+20191124: The USB names have changed on lpc176x, stm32, atsamd, and
-They now use the unique chip id by default.  Update the "serial"
+atsam.  They now use the unique chip id by default.  Update the
-setting in the "mcu" config section accordingly.
+"serial" setting in the "mcu" config section accordingly.
 
 20191121: The pressure_advance_lookahead_time parameter has been
 removed.  See example.cfg for alternate configuration settings.

src/atsam/Kconfig

@@ -11,6 +11,7 @@ config ATSAM_SELECT
     select HAVE_GPIO_SPI
     select HAVE_GPIO_HARD_PWM
     select HAVE_GPIO_BITBANGING
+    select HAVE_CHIPID
 
 config BOARD_DIRECTORY
     string

src/atsam/Makefile

@@ -28,7 +28,7 @@ src-y += generic/armcm_boot.c generic/armcm_irq.c generic/armcm_timer.c
 src-y += generic/crc16_ccitt.c
 usb-src-$(CONFIG_MACH_SAM3X) := atsam/sam3_usb.c
 usb-src-$(CONFIG_MACH_SAM4) := atsam/sam4_usb.c
-src-$(CONFIG_USBSERIAL) += $(usb-src-y) generic/usb_cdc.c
+src-$(CONFIG_USBSERIAL) += $(usb-src-y) atsam/chipid.c generic/usb_cdc.c
 src-$(CONFIG_SERIAL) += atsam/serial.c generic/serial_irq.c
 src-$(CONFIG_MACH_SAM3X) += atsam/adc.c
 src-$(CONFIG_MACH_SAM4S) += atsam/adc.c

src/atsam/chipid.c

@@ -0,0 +1,74 @@
+// Support for extracting the hardware chip id on sam3/sam4
+//
+// Copyright (C) 2019  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include "generic/irq.h" // irq_disable
+#include "generic/usb_cdc.h" // usb_fill_serial
+#include "generic/usbstd.h" // usb_string_descriptor
+#include "internal.h" // EFC0
+#include "sched.h" // DECL_INIT
+
+#define CHIP_UID_LEN 16
+
+static struct {
+    struct usb_string_descriptor desc;
+    uint16_t data[CHIP_UID_LEN * 2];
+} cdc_chipid;
+
+struct usb_string_descriptor *
+usbserial_get_serialid(void)
+{
+   return &cdc_chipid.desc;
+}
+
+// Compatibility definitions for sam4e8e
+#ifndef EFC0
+#define EFC0 EFC
+#define IFLASH0_ADDR IFLASH_ADDR
+#endif
+
+void noinline __section(".ramfunc.read_chip_id")
+read_chip_id(uint32_t *id)
+{
+    // Workaround sam3 errata
+    uint32_t fmr = EFC0->EEFC_FMR;
+    EFC0->EEFC_FMR = fmr | EEFC_FMR_SCOD;
+
+    // Send the STUI command
+    while (!(EFC0->EEFC_FSR & EEFC_FSR_FRDY))
+        ;
+    EFC0->EEFC_FCR = EEFC_FCR_FKEY_PASSWD | EEFC_FCR_FCMD_STUI;
+    while (EFC0->EEFC_FSR & EEFC_FSR_FRDY)
+        ;
+
+    // Copy the id
+    id[0] = *(uint32_t*)(IFLASH0_ADDR + 0x00);
+    id[1] = *(uint32_t*)(IFLASH0_ADDR + 0x04);
+    id[1] = *(uint32_t*)(IFLASH0_ADDR + 0x08);
+    id[1] = *(uint32_t*)(IFLASH0_ADDR + 0x0c);
+
+    // Send the SPUI command
+    EFC0->EEFC_FCR = EEFC_FCR_FKEY_PASSWD | EEFC_FCR_FCMD_SPUI;
+    while (!(EFC0->EEFC_FSR & EEFC_FSR_FRDY))
+        ;
+
+    // Restore fmr
+    EFC0->EEFC_FMR = fmr;
+}
+
+void
+chipid_init(void)
+{
+    if (!CONFIG_USB_SERIAL_NUMBER_CHIPID)
+        return;
+
+    uint32_t id[4];
+    irq_disable();
+    read_chip_id(id);
+    irq_enable();
+
+    usb_fill_serial(&cdc_chipid.desc, ARRAY_SIZE(cdc_chipid.data), id);
+}
+DECL_INIT(chipid_init);