Re: [PATCH 1/1] imx8m: ddr_init: fix reading of DDR4 MR registers

[Fabio Estevam]

Hi Paul,

On 19/10/2022 23:33, Ying-Chun Liu (PaulLiu) wrote:

Accorting to commit 290ffe57886271a6 we need to read more significant
bytes to get a non-zero value. However commit 7e9bd84883aeb1e2 removes
it by accident. Thus we add the changes back. This is needed to let
imx8mm-cl-iot-gate to boot correctly.

Signed-off-by: Ying-Chun Liu (PaulLiu) 


Rasmus has already submitted a fix for this:

https://lore.kernel.org/u-boot/f623aec6ff75744183ce86d0a6e17...@denx.de/T/#t

Thanks

[PATCH 1/1] imx8m: ddr_init: fix reading of DDR4 MR registers

[Ying-Chun Liu (PaulLiu)]

Accorting to commit 290ffe57886271a6 we need to read more significant
bytes to get a non-zero value. However commit 7e9bd84883aeb1e2 removes
it by accident. Thus we add the changes back. This is needed to let
imx8mm-cl-iot-gate to boot correctly.

Signed-off-by: Ying-Chun Liu (PaulLiu) 
Cc: Fabio Estevam 
Cc: Marek Vasut 
Cc: Peng Fan 
Cc: Rasmus Villemoes 
Cc: Stefano Babic 
Cc: NXP i.MX U-Boot Team 
---
 drivers/ddr/imx/imx8m/ddr_init.c | 8 +++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/ddr/imx/imx8m/ddr_init.c b/drivers/ddr/imx/imx8m/ddr_init.c
index d964184ddc..7a683b1d36 100644
--- a/drivers/ddr/imx/imx8m/ddr_init.c
+++ b/drivers/ddr/imx/imx8m/ddr_init.c
@@ -134,8 +134,14 @@ 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;
 }
-- 
2.35.1