In simple cases we can instantiate SPD EEPROMs on the SMBus
automatically. Start with just DDR2, DDR3 and DDR4 on x86 for now,
and only for systems with no more than 4 memory slots. These
limitations may be lifted later.
Signed-off-by: Jean Delvare <jdelvare@xxxxxxx>
---
drivers/i2c/i2c-smbus.c | 104 +++++++++++++++++++++++++++++++++++++++++++++-
include/linux/i2c-smbus.h | 11 ++++
2 files changed, 113 insertions(+), 2 deletions(-)
--- linux-5.3.orig/drivers/i2c/i2c-smbus.c 2019-10-04 15:04:16.601640711 +0200
+++ linux-5.3/drivers/i2c/i2c-smbus.c 2019-10-11 13:01:59.596425003 +0200
@@ -3,10 +3,11 @@
* i2c-smbus.c - SMBus extensions to the I2C protocol
*
* Copyright (C) 2008 David Brownell
- * Copyright (C) 2010 Jean Delvare <jdelvare@xxxxxxx>
+ * Copyright (C) 2010-2019 Jean Delvare <jdelvare@xxxxxxx>
*/
#include <linux/device.h>
+#include <linux/dmi.h>
#include <linux/i2c.h>
#include <linux/i2c-smbus.h>
#include <linux/interrupt.h>
@@ -203,6 +204,107 @@ EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert
module_i2c_driver(smbalert_driver);
+/*
+ * SPD is not part of SMBus but we include it here for convenience as the
+ * target systems are the same.
+ * Restrictions to automatic SPD instantiation:
+ * - Only works if all filled slots have the same memory type
+ * - Only works for DDR2, DDR3 and DDR4 for now
+ * - Only works on systems with 1 to 4 memory slots
+ */
+#if IS_ENABLED(CONFIG_DMI)
+void i2c_register_spd(struct i2c_adapter *adap)
+{
+ int n, slot_count = 0, dimm_count = 0;
+ u16 handle;
+ u8 common_mem_type = 0x0, mem_type;
+ u64 mem_size;
+ const char *name;
+
+ while ((handle = dmi_memdev_handle(slot_count)) != 0xffff) {
+ slot_count++;
+
+ /* Skip empty slots */
+ mem_size = dmi_memdev_size(handle);
+ if (!mem_size)
+ continue;
+
+ /* Skip undefined memory type */
+ mem_type = dmi_memdev_type(handle);
+ if (mem_type <= 0x02) /* Invalid, Other, Unknown */
+ continue;
+
+ if (!common_mem_type) {
+ /* First filled slot */
+ common_mem_type = mem_type;
+ } else {
+ /* Check that all filled slots have the same type */
+ if (mem_type != common_mem_type) {
+ dev_warn(&adap->dev,
+ "Different memory types mixed, not instantiating SPD\n");
+ return;
+ }
+ }
+ dimm_count++;
+ }
+
+ /* No useful DMI data, bail out */
+ if (!dimm_count)
+ return;
+
+ dev_info(&adap->dev, "%d/%d memory slots populated (from DMI)\n",
+ dimm_count, slot_count);
+
+ if (slot_count > 4) {
+ dev_warn(&adap->dev,
+ "Systems with more than 4 memory slots not supported yet, not instantiating SPD\n");
+ return;
+ }
+
+ switch (common_mem_type) {
+ case 0x13: /* DDR2 */
+ case 0x18: /* DDR3 */
+ case 0x1C: /* LPDDR2 */
+ case 0x1D: /* LPDDR3 */
+ name = "spd";
+ break;
+ case 0x1A: /* DDR4 */
+ case 0x1E: /* LPDDR4 */
+ name = "ee1004";
+ break;
+ default:
+ dev_info(&adap->dev,
+ "Memory type 0x%02x not supported yet, not instantiating SPD\n",
+ common_mem_type);
+ return;
+ }
+
+ /*
+ * We don't know in which slots the memory modules are. We could
+ * try to guess from the slot names, but that would be rather complex
+ * and unreliable, so better probe all possible addresses until we
+ * have found all memory modules.
+ */
+ for (n = 0; n < slot_count && dimm_count; n++) {
+ struct i2c_board_info info;
+ unsigned short addr_list[2];
+
+ memset(&info, 0, sizeof(struct i2c_board_info));
+ strlcpy(info.type, name, I2C_NAME_SIZE);
+ addr_list[0] = 0x50 + n;
+ addr_list[1] = I2C_CLIENT_END;
+
+ if (i2c_new_probed_device(adap, &info, addr_list, NULL)) {
+ dev_info(&adap->dev,
+ "Successfully instantiated SPD at 0x%hx\n",
+ addr_list[0]);
+ dimm_count--;
+ }
+ }
+}
+EXPORT_SYMBOL_GPL(i2c_register_spd);
+#endif
+
MODULE_AUTHOR("Jean Delvare <jdelvare@xxxxxxx>");
MODULE_DESCRIPTION("SMBus protocol extensions support");
MODULE_LICENSE("GPL");
--- linux-5.3.orig/include/linux/i2c-smbus.h 2019-10-04 15:04:16.601640711 +0200
+++ linux-5.3/include/linux/i2c-smbus.h 2019-10-11 11:03:51.432166962 +0200
@@ -2,7 +2,7 @@
/*
* i2c-smbus.h - SMBus extensions to the I2C protocol
*
- * Copyright (C) 2010 Jean Delvare <jdelvare@xxxxxxx>
+ * Copyright (C) 2010-2019 Jean Delvare <jdelvare@xxxxxxx>
*/
#ifndef _LINUX_I2C_SMBUS_H
@@ -42,6 +42,15 @@ static inline int of_i2c_setup_smbus_ale
{
return 0;
}
+#endif
+
+#if IS_ENABLED(CONFIG_I2C_SMBUS) && IS_ENABLED(CONFIG_DMI)
+void i2c_register_spd(struct i2c_adapter *adap);
+#else
+static void i2c_register_spd(struct i2c_adapter *adap)
+{
+ return 0;
+}
#endif
#endif /* _LINUX_I2C_SMBUS_H */
--
Jean Delvare
SUSE L3 Support
