board: starfive: function to read eMMC size

The EEPROM provides information about the size of the eMMC.
Provide a new function get_mmc_size_from_eeprom() to read it.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: E. Shattow <lucent@gmail.com>

arch/riscv/include/asm/arch-jh7110/eeprom.h

@@ -12,6 +12,13 @@
 u8 get_pcb_revision_from_eeprom(void);
 u32 get_ddr_size_from_eeprom(void);
 
+/**
+ * get_mmc_size_from_eeprom() - read eMMC size from EEPROM
+ *
+ * @return: size in GiB or 0 on error.
+ */
+u32 get_mmc_size_from_eeprom(void);
+
 /**
  * get_product_id_from_eeprom - get product ID string
  *

board/starfive/visionfive2/Kconfig

@@ -50,4 +50,13 @@ config BOARD_SPECIFIC_OPTIONS # dummy
 	imply PHY_LIB
 	imply PHY_MSCC
 
+config STARFIVE_NO_EMMC
+	bool "Report eMMC size as zero"
+	help
+	  The serial number string in the EEPROM is meant to report the
+	  size of onboard eMMC. Unfortunately some Milk-V Mars CM Lite
+	  modules without eMMC show a non-zero size here.
+
+	  Set to 'Y' if you have a Mars CM Lite module.
+
 endif

board/starfive/visionfive2/visionfive2-i2c-eeprom.c

@@ -548,6 +548,24 @@ u32 get_ddr_size_from_eeprom(void)
 	return hextoul(&pbuf.eeprom.atom1.data.pstr[14], NULL);
 }
 
+u32 get_mmc_size_from_eeprom(void)
+{
+	u32 size;
+
+	if (IS_ENABLED(CONFIG_STARFIVE_NO_EMMC))
+		return 0;
+
+	if (read_eeprom())
+		return 0;
+
+	size = dectoul(&pbuf.eeprom.atom1.data.pstr[19], NULL);
+
+	if (pbuf.eeprom.atom1.data.pstr[21] == 'T')
+		size <<= 10;
+
+	return size;
+}
+
 U_BOOT_LONGHELP(mac,
 	"\n"
 	"    - display EEPROM content\n"