[PATCH] i2c: smbus: Support up to 8 SPD EEPROMs

[PATCH] i2c: smbus: Support up to 8 SPD EEPROMs

[Jean Delvare]

I originally restricted i2c_register_spd() to only support systems
with up to 4 memory slots, so that we can experiment with it on
a limited numbers of systems. It's been more than 3 years and it
seems to work just fine, so the time has come to lift this arbitrary
limitation.

The maximum number of memory slots which can be connected to a single
I2C segment is 8, so support that many SPD EEPROMs. Any system with
more than 8 memory slots would have either multiple SMBus channels
or SMBus multiplexing, so it would need dedicated care. We'll get to
that later as needed.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: Heiner Kallweit <hkallweit1@gmail.com>
Cc: Wolfram Sang <wsa@kernel.org>
---
 drivers/i2c/i2c-smbus.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- linux-6.6.orig/drivers/i2c/i2c-smbus.c
+++ linux-6.6/drivers/i2c/i2c-smbus.c
@@ -308,8 +308,8 @@ EXPORT_SYMBOL_GPL(i2c_free_slave_host_no
  * 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
+ *  - Only works for DDR, DDR2, DDR3 and DDR4 for now
+ *  - Only works on systems with 1 to 8 memory slots
  */
 #if IS_ENABLED(CONFIG_DMI)
 void i2c_register_spd(struct i2c_adapter *adap)
@@ -354,9 +354,9 @@ void i2c_register_spd(struct i2c_adapter
 	dev_info(&adap->dev, "%d/%d memory slots populated (from DMI)\n",
 		 dimm_count, slot_count);
 
-	if (slot_count > 4) {
+	if (slot_count > 8) {
 		dev_warn(&adap->dev,
-			 "Systems with more than 4 memory slots not supported yet, not instantiating SPD\n");
+			 "Systems with more than 8 memory slots not supported yet, not instantiating SPD\n");
 		return;
 	}
 


-- 
Jean Delvare
SUSE L3 Support

Re: [PATCH] i2c: smbus: Support up to 8 SPD EEPROMs

[Wolfram Sang]

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On Tue, Nov 14, 2023 at 03:13:28PM +0100, Jean Delvare wrote:
> I originally restricted i2c_register_spd() to only support systems
> with up to 4 memory slots, so that we can experiment with it on
> a limited numbers of systems. It's been more than 3 years and it
> seems to work just fine, so the time has come to lift this arbitrary
> limitation.
> 
> The maximum number of memory slots which can be connected to a single
> I2C segment is 8, so support that many SPD EEPROMs. Any system with
> more than 8 memory slots would have either multiple SMBus channels
> or SMBus multiplexing, so it would need dedicated care. We'll get to
> that later as needed.
> 
> Signed-off-by: Jean Delvare <jdelvare@suse.de>
> Cc: Heiner Kallweit <hkallweit1@gmail.com>
> Cc: Wolfram Sang <wsa@kernel.org>

Applied to for-next, thanks!


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