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Message-Id: <20240629173716.20389-2-linux@roeck-us.net>
Date: Sat, 29 Jun 2024 10:37:16 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: linux-kernel@...r.kernel.org
Cc: Arnd Bergmann <arnd@...db.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Guenter Roeck <linux@...ck-us.net>,
Heiner Kallweit <hkallweit1@...il.com>,
Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH 2/2] eeprom: ee1004: Instantiate jc42 devices for DIMMS implementing Rev.1 SPD
DDR4 DIMMS implementing SPD Annex L, Revision 1 do not implement SPD byte
14 (Module Temperature Sensor); this byte was only added in revision 2 of
the standard. This only applies to DDR4, not DDR4E or LPDDR4, since those
DDR types were only introduced in revision 3 of the standard.
Use this information to instantiate the jc42 device if the module is a DDR4
following SPD revision 1.0 and a device is detected at the expected thermal
sensor address, even if the Module Temperature Sensor byte suggests that
the thermal sensor is not supported.
Cc: Heiner Kallweit <hkallweit1@...il.com>
Cc: Thomas Weißschuh <linux@...ssschuh.net>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
---
drivers/misc/eeprom/ee1004.c | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)
diff --git a/drivers/misc/eeprom/ee1004.c b/drivers/misc/eeprom/ee1004.c
index 71ca66d1df82..a39fefb066cd 100644
--- a/drivers/misc/eeprom/ee1004.c
+++ b/drivers/misc/eeprom/ee1004.c
@@ -187,14 +187,31 @@ static void ee1004_probe_temp_sensor(struct i2c_client *client)
struct i2c_board_info info = { .type = "jc42" };
unsigned short addr = 0x18 | (client->addr & 7);
unsigned short addr_list[] = { addr, I2C_CLIENT_END };
- u8 byte14;
+ u8 data[2];
int ret;
/* byte 14, bit 7 is set if temp sensor is present */
- ret = ee1004_eeprom_read(client, &byte14, 14, 1);
- if (ret != 1 || !(byte14 & BIT(7)))
+ ret = ee1004_eeprom_read(client, data, 14, 1);
+ if (ret != 1)
return;
+ if (!(data[0] & BIT(7))) {
+ /*
+ * If the SPD data suggests that there is no temperature
+ * sensor, it may still be there for SPD revision 1.0.
+ * See SPD Annex L, Revision 1 and 2, for details.
+ * Check DIMM type and SPD revision; if it is a DDR4
+ * with SPD revision 1.0, check the thermal sensor address
+ * and instantiate the jc42 driver if a chip is found at
+ * that address.
+ * It is not necessary to check if there is a chip at the
+ * temperature sensor address since i2c_new_scanned_device()
+ * will do that and return silently if no chip is found.
+ */
+ ret = ee1004_eeprom_read(client, data, 1, 2);
+ if (ret != 2 || data[0] != 0x10 || data[1] != 0x0c)
+ return;
+ }
i2c_new_scanned_device(client->adapter, &info, addr_list, NULL);
}
--
2.39.2
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