From 9121680204c9b8a1caf12995a35ebaa8d2306838 Mon Sep 17 00:00:00 2001
From: Benjamin Valentin <benjamin.valentin@ml-pa.com>
Date: Mon, 21 Feb 2022 15:13:29 +0100
Subject: [PATCH 1/2] cpu/sam0_common: decode model number

---
 cpu/sam0_common/sam0_info.mk | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
 create mode 100644 cpu/sam0_common/sam0_info.mk

diff --git a/cpu/sam0_common/sam0_info.mk b/cpu/sam0_common/sam0_info.mk
new file mode 100644
index 0000000000..7113168db3
--- /dev/null
+++ b/cpu/sam0_common/sam0_info.mk
@@ -0,0 +1,14 @@
+# Extract SAM0 infos from CPU_MODEL
+# Example for saml21e15b
+# - SAM0_FAMILY:  l
+# - SAM0_SERIES:  21
+# - SAM0_PINCNT:  e  (32 Pins)
+# - SAM0_DENSITY: 15 (32k Flash)
+# - SAM0_VARIANT: b  (release stepping)
+
+SAM0_INFO    := $(shell echo $(CPU_MODEL) | sed -E -e 's/^sam(d|e|l|r)([0-9][0-9])([a-z])([0-9][0-9])(.)?/\1 \2 \3 \4 \5/')
+SAM0_FAMILY  := $(word 1, $(SAM0_INFO))
+SAM0_SERIES  := $(word 2, $(SAM0_INFO))
+SAM0_PINCNT  := $(word 3, $(SAM0_INFO))
+SAM0_DENSITY := $(word 4, $(SAM0_INFO))
+SAM0_VARIANT := $(word 5, $(SAM0_INFO))

From c44cf1423e0b8dfb8f00c7a530e4ca6105f729d0 Mon Sep 17 00:00:00 2001
From: Benjamin Valentin <benjamin.valentin@ml-pa.com>
Date: Mon, 21 Feb 2022 15:14:35 +0100
Subject: [PATCH 2/2] cpu/saml21: derive low power SRAM length from model
 number

---
 cpu/saml21/Makefile.include | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/cpu/saml21/Makefile.include b/cpu/saml21/Makefile.include
index 1bd1b002dd..97493cfa5d 100644
--- a/cpu/saml21/Makefile.include
+++ b/cpu/saml21/Makefile.include
@@ -1,3 +1,5 @@
+include $(RIOTCPU)/sam0_common/sam0_info.mk
+
 ifneq (,$(filter saml21%a,$(CPU_MODEL)))
   CFLAGS += -DCPU_SAML21A
 endif
@@ -13,9 +15,15 @@ endif
 
 CFLAGS += -DCPU_COMMON_SAML21
 
-ifneq (,$(filter saml21j18b saml21j18a samr30g18a samr34j18b,$(CPU_MODEL)))
-  BACKUP_RAM_ADDR = 0x30000000
-  BACKUP_RAM_LEN  = 0x2000
+BACKUP_RAM_ADDR = 0x30000000
+ifeq (18, $(SAM0_DENSITY))
+  BACKUP_RAM_LEN  = 0x2000  # 8k
+else ifeq (17, $(SAM0_DENSITY))
+  BACKUP_RAM_LEN  = 0x2000  # 8k
+else ifeq (16, $(SAM0_DENSITY))
+  BACKUP_RAM_LEN  = 0x1000  # 4k
+else ifeq (15, $(SAM0_DENSITY))
+  BACKUP_RAM_LEN  =  0x800  # 2k
 endif
 
 include $(RIOTCPU)/sam0_common/Makefile.include