linux-kernel - Re: [PATCH] i2c: smbus: support new RAM variant for SPD

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Date:   Mon, 14 Nov 2022 10:17:54 +0100
From:   Corentin LABBE <clabbe@...libre.com>
To:     Jean Delvare <jdelvare@...e.de>
Cc:     wsa@...nel.org, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: smbus: support new RAM variant for SPD

Le Tue, Nov 08, 2022 at 11:48:51AM +0100, Jean Delvare a écrit :
> Hi Corentin,
> 
> On Mon,  7 Nov 2022 16:06:02 +0000, Corentin Labbe wrote:
> > On my x05 laptop I got:
> > Memory type 0x12 not supported yet, not instantiating SPD
> 
> 
> Oh, that one must be old.
> 
> > Adding the 0x12 case lead to a successful instantiated SPD AT24 EEPROM.
> > i801_smbus 0000:00:1f.3: SMBus using polling
> > i2c i2c-6: 2/2 memory slots populated (from DMI)
> > at24 6-0050: 256 byte spd EEPROM, read-only
> > i2c i2c-6: Successfully instantiated SPD at 0x50
> > at24 6-0051: 256 byte spd EEPROM, read-only
> > i2c i2c-6: Successfully instantiated SPD at 0x51
> > 
> > And then, I decoded it successfully via decode-dimms.
> > 
> > Signed-off-by: Corentin Labbe <clabbe@...libre.com>
> > ---
> > The result of decode-dimms could be found at http://kernel.montjoie.ovh/zoo/x05/decode-dimms.txt
> > Since RAM is DDR, I wanted to add '/* DDR */' comment, but I didnt find any document with
> > proof that this 0x12 is for DDR.
> 
> It is. The document you are looking for is:
> https://www.dmtf.org/sites/default/files/standards/documents/DSP0134_3.6.0.pdf
> 
> and specifically section 7.18.2 (Memory Device — Type), table 78
> (Memory Device: Type).
> 

Hello

Thanks for the link, I will add it also as comment.

> > 
> >  drivers/i2c/i2c-smbus.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/drivers/i2c/i2c-smbus.c b/drivers/i2c/i2c-smbus.c
> > index 07c92c8495a3..6dca19c994db 100644
> > --- a/drivers/i2c/i2c-smbus.c
> > +++ b/drivers/i2c/i2c-smbus.c
> > @@ -362,6 +362,7 @@ void i2c_register_spd(struct i2c_adapter *adap)
> >  	}
> >  
> >  	switch (common_mem_type) {
> > +	case 0x12:
> >  	case 0x13:	/* DDR2 */
> >  	case 0x18:	/* DDR3 */
> >  	case 0x1C:	/* LPDDR2 */
> 
> Please also add LPDDR (0x1B) for consistency.


Will do it.

Thanks
Regards