[coreboot] Patch set updated for coreboot: fd0b849 Exynos5250: make vendor enums in the timing array more debuggable.

Ronald G. Minnich (rminnich@gmail.com) gerrit at coreboot.org
Tue Jan 29 23:09:33 CET 2013

Ronald G. Minnich (rminnich at gmail.com) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/2221


commit fd0b849df28aedd943e0e96ff8ca4972372f66d1
Author: Ronald G. Minnich <rminnich at gmail.com>
Date:   Tue Jan 29 11:52:05 2013 -0800

    Exynos5250: make vendor enums in the timing array more debuggable.
    The timing array is crucial to proper operation of DRAM.
    Getting a valid
    pointer to it is hence very important. Unfortunately, the constants
    chosen for the vendor were '1', and '2', (this in a 32-bit word) which
    in a debug print makes it almost impossible to tell if you've got a
    misaligned pointer. Note: coreboot people did not choose them :-)
    So, give them values which are extremely unlikely to occur elsewhere
    in the array (or in memory, for that matter).
    Given the frequency with which this check occurs, i.e. once,
    I would much prefer strings
    but I expect I'd get shouted down on that one. Constants in this case
    are an almost useless optimization but we'll go with them for now. Note
    no space is saved by not using strings: there's an entire function somewhere
    devoted to mapping the enum to a string!
    Debug prints of pointers to structs in this array are now far more
    useful than they were.
    See snarky comment in the code (left there to make sure nobody gets
    tempted to get fancy again). Comment now less snarky.
    This is tested on google snow to the point that the DRAM works.
    Change-Id: I30bc44719f321f791fd82ded60e29393399d9e3d
    Signed-off-by: Ronald G. Minnich <rminnich at gmail.com>
 src/cpu/samsung/exynos5250/dmc.h | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/src/cpu/samsung/exynos5250/dmc.h b/src/cpu/samsung/exynos5250/dmc.h
index d1dfbb1..b778e09 100644
--- a/src/cpu/samsung/exynos5250/dmc.h
+++ b/src/cpu/samsung/exynos5250/dmc.h
@@ -152,12 +152,27 @@ enum ddr_mode {
+/* For reasons unknown, people are in the habit of taking a 32-bit
+ * field with 2 possible values and packing it with, say, 2 bits. A
+ * non-robust encoding, using only 2 bits of a 32-bit field, is
+ * incredibly difficult to deal with when things go wrong, because
+ * there are a lot of things that get expressed as 0, 1, or 2. If
+ * you're scanning with jtag or dumping memory it is really hard to
+ * tell when you've hit the beginning of the struct. So, let's be a
+ * bit smart here. First, while it's common to let the enum count
+ * entries for you, when there are two of them, we can do the
+ * counting. And, let's set the values to something we can easily scan
+ * for in memory. Since '1' and '2' are rather common, we pick
+ * something that's actually of some value when things go wrong.  This
+ * setup motivated by a use case: something's going wrong and having a
+ * manuf name of '1' or '2' is completely useless!
+ */
 enum mem_manuf {
+	MEM_MANUF_ELPIDA = 0xe7b1da,
+	MEM_MANUF_SAMSUNG = 0x5a5096,
+	MEM_MANUF_COUNT = 2, // fancy that.
 /* CONCONTROL register fields */

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