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Re: [PATCH 2/2] i2c/smbus_eeprom: Add feature bit to SPD data

From: BALATON Zoltan
Subject: Re: [PATCH 2/2] i2c/smbus_eeprom: Add feature bit to SPD data
Date: Sun, 18 Jul 2021 22:39:16 +0200 (CEST)

On Sun, 18 Jul 2021, Corey Minyard wrote:
On Thu, Jul 15, 2021 at 06:50:44PM +0200, BALATON Zoltan wrote:
Add the differential clock input feature bit to the generated SPD
data. Most guests don't seem to care but pegasos2 firmware version 1.2
checks for this bit and stops with unsupported module type error if
it's not present. Since this feature is likely present on real memory
modules add it in the general code rather than patching the generated
SPD data in pegasos2 board only.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>

I checked this all out and it looks correct to me.  I can take it in my
tree, if necessary.  Feature freeze is in two days, so probably not for
6.1, though it could be pushed into there if its needed in 6.1.


Acked-by: Corey Minyard <cminyard@mvista.com>

Thanks. As this fixes pegasos2 ROM 1.2 that some users may find instead of the 1.1 version I consider this a bugfix not a feature and would like to get merged for 6.1 if possible (hopefully can be in David's tree with the other patch that's also a bugfix) because that way it won't happen that some users will get problems if they find the wrong ROM. With this patch both versions available on line work so there should be no problem for anyone. Other firmware ROMs don't seem to care so they're unlikely to break and the only machines using it now are pegasos2, sam460ex and fuloong2e and only when using firmware ROM so this does not need to wait until 6.2 I think as 6.1 is the first version pegasos2 is available and it would be nice to get it working well in the first version.


if someone else wants to take it.  This particular code really doesn't
belong in eeprom.c, I don't think, but I'm not sure where else to put
it.  And I can look in the SPD tables as well as anyone :).


I've tested it with the firmware of pegasos2, sam460ex, fuloong2e and
g3beige (latter is not upstream yet) that are the only ones using this
function currently. Probably this could go in via PPC tree with my
other pegasos2 fix if respective maitainers ack this patch.

 hw/i2c/smbus_eeprom.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/i2c/smbus_eeprom.c b/hw/i2c/smbus_eeprom.c
index 4d2bf99207..12c5741f38 100644
--- a/hw/i2c/smbus_eeprom.c
+++ b/hw/i2c/smbus_eeprom.c
@@ -276,7 +276,7 @@ uint8_t *spd_data_generate(enum sdram_type type, ram_addr_t 
     spd[18] = 12;   /* ~CAS latencies supported */
     spd[19] = (type == DDR2 ? 0 : 1); /* reserved / ~CS latencies supported */
     spd[20] = 2;    /* DIMM type / ~WE latencies */
-                    /* module features */
+    spd[21] = (type < DDR2 ? 0x20 : 0); /* module features */
                     /* memory chip features */
     spd[23] = 0x12; /* clock cycle time @ medium CAS latency */
                     /* data access time */

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