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imx8m: fix reading of DDR4 MR registers

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I was trying to employ lpddr4_mr_read() to something similar to what
the imx8mm-cl-iot-gate board is doing for auto-detecting the RAM
type. However, the version in drivers/ddr/imx/imx8m/ddrphy_utils.c
differs from the private one used by that board in how it extracts the
byte value, and I was only getting zeroes. Adding a bit of debug
printf'ing gives me

 tmp = 0x00ffff00
 tmp = 0x00070700
 tmp = 0x00000000
 tmp = 0x00101000

and indeed I was expecting a (combined) value of 0xff070010 (0xff
being Manufacturer ID for Micron). I can't find any documentation that
says how the values are supposed to be read, but clearly the iot-gate
definition is the right one, both for its use case as well as my
imx8mp-based board.

So lift the private definition of lpddr4_mr_read() from the
imx8mm-cl-iot-gate board code to ddrphy_utils.c, and add a declaration
in the ddr.h header where e.g. get_trained_CDD() is already declared.

This has only been compile-tested for the imx8mm-cl-iot-gate
board (since I don't have the hardware), but since I've merely moved
its definition of lpddr4_mr_read(), I'd be surprised if it changed
anything for that board.

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Tested-by: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
Reviewed-by: Fabio Estevam <festevam@denx.de>
This commit is contained in:
Rasmus Villemoes
2022-04-25 16:22:48 +02:00
committed by Stefano Babic
parent c329f9349b
commit 290ffe5788
3 changed files with 8 additions and 29 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
drivers/ddr/imx/imx8m/ddrphy_utils.c
View File

@@ -198,9 +198,14 @@ unsigned int lpddr4_mr_read(unsigned int mr_rank, unsigned int mr_addr)
tmp = reg32_read(DRC_PERF_MON_MRR0_DAT(0));
} while ((tmp & 0x8) == 0);
tmp = reg32_read(DRC_PERF_MON_MRR1_DAT(0));
tmp = tmp & 0xff;
reg32_write(DRC_PERF_MON_MRR0_DAT(0), 0x4);
while (tmp) { //try to find a significant byte in the word
if (tmp & 0xff) {
tmp &= 0xff;
break;
}
tmp >>= 8;
}
return tmp;
}