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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@gmail.com> Cc: Thomas Weißschuh <linux@weissschuh.net> Signed-off-by: Guenter Roeck <linux@roeck-us.net> Link: https://lore.kernel.org/r/20240629173716.20389-2-linux@roeck-us.net Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -186,14 +186,31 @@ static void ee1004_probe_temp_sensor(struct i2c_client *client)
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struct i2c_board_info info = { .type = "jc42" };
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unsigned short addr = 0x18 | (client->addr & 7);
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unsigned short addr_list[] = { addr, I2C_CLIENT_END };
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u8 byte14;
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u8 data[2];
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int ret;
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/* byte 14, bit 7 is set if temp sensor is present */
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ret = ee1004_eeprom_read(client, &byte14, 14, 1);
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if (ret != 1 || !(byte14 & BIT(7)))
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ret = ee1004_eeprom_read(client, data, 14, 1);
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if (ret != 1)
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return;
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if (!(data[0] & BIT(7))) {
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/*
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* If the SPD data suggests that there is no temperature
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* sensor, it may still be there for SPD revision 1.0.
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* See SPD Annex L, Revision 1 and 2, for details.
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* Check DIMM type and SPD revision; if it is a DDR4
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* with SPD revision 1.0, check the thermal sensor address
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* and instantiate the jc42 driver if a chip is found at
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* that address.
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* It is not necessary to check if there is a chip at the
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* temperature sensor address since i2c_new_scanned_device()
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* will do that and return silently if no chip is found.
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*/
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ret = ee1004_eeprom_read(client, data, 1, 2);
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if (ret != 2 || data[0] != 0x10 || data[1] != 0x0c)
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return;
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}
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i2c_new_scanned_device(client->adapter, &info, addr_list, NULL);
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}
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