[U-Boot] [PATCH] ppc4xx: Fix initialization of SDRAM_CODT register in ppc_4xx_ddr2.c

[carolyn.j.smith at tektronix.com]

Okay, I will resubmit my patch.

Carolyn

>-----Original Message-----
>From: Adam Graham [mailto:agraham at amcc.com]
>Sent: Tuesday, January 27, 2009 11:22 PM
>To: Stefan Roese; u-boot at lists.denx.de
>Cc: Smith, Carolyn J; Adam Graham; Victor Gallardo
>Subject: RE: [U-Boot] [PATCH] ppc4xx: Fix initialization of
>SDRAM_CODT register in ppc_4xx_ddr2.c
>
>Stefan, Carolyn,
>
>Yes, I do intend on sending out an AMCC patch to remove the definition
>for SDRAM_CODT_FEEBBACK_RCV_SINGLE_END and
>SDRAM_CODT_FEEBBACK_DRV_SINGLE_END.
>
>My apologies Carolyn as I should have notified you of this intent.
>
>My AMCC patch to remove these SDRAM_CODT bit definitions may come after
>your patch Carolyn, so in your patch do not include the usage of these
>(SDRAM_CODT_FEEBBACK_RCV_SINGLE_END and
>SDRAM_CODT_FEEBBACK_DRV_SINGLE_END) bits.
>
>According to our AMCC PPC4xx chip hardware designers, the SDRAM_CODT IP
>feedback signal is single ended (i.e. SDRAM_CODT bits 29 and 30).
>
>The PPC4xx SDRAM_CODT bits 29 and 30 are reserved
>non-changeable bits as
>they are set in the IP to single-ended mode:
>
>SDRAM_CODT bit 29  0 Sets feedback receiver to differential mode
>                   1 Sets feedback receiver to single ended mode (mode
>set for the AMCC 4xx SoC chips)
>           bit 30  0 Sets feedback driver to differential mode
>                   1 Sets feedback driver to single ended mode   (mode
>set for the AMCC 4xx SoC chips)
>
>
>Best,
>Adam
>
>> -----Original Message-----
>> From: Stefan Roese [mailto:sr at denx.de]
>> Sent: Monday, January 26, 2009 9:47 PM
>> To: u-boot at lists.denx.de
>> Cc: carolyn.j.smith at tektronix.com; Adam Graham
>> Subject: Re: [U-Boot] [PATCH] ppc4xx: Fix initialization of
>> SDRAM_CODT register in ppc_4xx_ddr2.c
>>
>> On Monday 26 January 2009, carolyn.j.smith at tektronix.com wrote:
>> > This fixes the initialization of the SDRAM_CODT register in
>> the ppc4xx
>> > DDR2 initialization code. The changes were discussed with
>> Stefan Roese
>> > and Adam Graham and tested by Adam.
>>
>> General comment: The line "The changes were discussed..."
>> should be placed below the "---" since it doesn't really
>> belong to the patch description.
>>
>> > Signed-off-by: Carolyn Smith <carolyn.smith at tektronix.com>
>> > ---
>> > diff -w -uprN old/cpu/ppc4xx/44x_spd_ddr2.c
>> new/cpu/ppc4xx/44x_spd_ddr2.c
>> > --- old/cpu/ppc4xx/44x_spd_ddr2.c       2009-01-20
>> 13:00:33.000000000 -0800
>> > +++ new/cpu/ppc4xx/44x_spd_ddr2.c       2009-01-23
>> 16:00:49.000000000 -0800
>> > @@ -1104,11 +1104,14 @@ static void program_codt(unsigned long *
>> >          * Set the SDRAM Controller On Die Termination Register
>> >
>> >
>*-----------------------------------------------------------------*/
>> > mfsdram(SDRAM_CODT, codt);
>> > -       codt |= (SDRAM_CODT_IO_NMODE
>> > -                & (~SDRAM_CODT_DQS_SINGLE_END
>> > -                   & ~SDRAM_CODT_CKSE_SINGLE_END
>> > -                   & ~SDRAM_CODT_FEEBBACK_RCV_SINGLE_END
>> > -                   & ~SDRAM_CODT_FEEBBACK_DRV_SINGLE_END));
>> > +
>> > +       codt |= SDRAM_CODT_IO_NMODE;
>> > +
>> > +       codt &= ~(SDRAM_CODT_DQS_SINGLE_END |
>> > +                 SDRAM_CODT_CKSE_SINGLE_END |
>> > +                 SDRAM_CODT_FEEBBACK_RCV_SINGLE_END |
>> > +                 SDRAM_CODT_FEEBBACK_DRV_SINGLE_END);
>> > +
>>
>> I don't think that this is correct. As I understood from
>> Adam, those bits it questions are undefined/reserevd on all
>> 4xx PPC's. So we should better remove the code referencing
>> those values. Here is what Adam wrote:
>>
>> > It is in fact the case for all the AMCC 4xx SoC chips that have the
>> > IBM SDRAM memory controller core IP, the SDRAM_CODT
>> register, bits 29
>> > and 30 are reserved bits.  Thanks Carolyn for finding this
>> issue.  We
>> > will update the 44x_spd_ddr2.c file and send out a patch
>> shortly for
>> > this SDRAM_CODT register bits 29-30 issue.
>>
>> Adam, do you still plan to send a patch for this? Or did I
>> misunderstand you and the patch above is ok?
>>
>> Thanks.
>>
>> Best regards,
>> Stefan
>>
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>
>