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Subject[PATCH] pm: at91: Workaround DDRSDRC self-refresh bug with LPDDR1 memories
Date
From: Peter Rosin <peda@axentia.se>

The DDRSDR controller (on the ATSAMA5D31) fails miserably to put LPDDR1
memories in self-refresh. Force the controller to think it has DDR2
memories during the self-refresh period, as the DDR2 self-refresh spec
is equivalent to LPDDR1, and is correctly implemented in the controller.

Assume that the second controller has the same fault, and that other
CPUs in the family has the same problem, but that is untested.

Signed-off-by: Peter Rosin <peda@axentia.se>
---
arch/arm/mach-at91/pm_slowclock.S | 43 +++++++++++++++++++++++++++++++-----
include/soc/at91/at91sam9_ddrsdr.h | 2 +-
2 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/arch/arm/mach-at91/pm_slowclock.S b/arch/arm/mach-at91/pm_slowclock.S
index 20018779bae7..63a9e0b0a17d 100644
--- a/arch/arm/mach-at91/pm_slowclock.S
+++ b/arch/arm/mach-at91/pm_slowclock.S
@@ -143,6 +143,16 @@ ddr_sr_enable:
cmp memctrl, #AT91_MEMCTRL_DDRSDR
bne sdr_sr_enable

+ /* LPDDR1 --> force DDR2 mode during self-refresh */
+ ldr tmp1, [sdramc, #AT91_DDRSDRC_MDR]
+ str tmp1, .saved_sam9_mdr
+ bic tmp1, tmp1, #~AT91_DDRSDRC_MD
+ cmp tmp1, #AT91_DDRSDRC_MD_LOW_POWER_DDR
+ ldreq tmp1, [sdramc, #AT91_DDRSDRC_MDR]
+ biceq tmp1, tmp1, #AT91_DDRSDRC_MD
+ orreq tmp1, tmp1, #AT91_DDRSDRC_MD_DDR2
+ streq tmp1, [sdramc, #AT91_DDRSDRC_MDR]
+
/* prepare for DDRAM self-refresh mode */
ldr tmp1, [sdramc, #AT91_DDRSDRC_LPR]
str tmp1, .saved_sam9_lpr
@@ -151,14 +161,26 @@ ddr_sr_enable:

/* figure out if we use the second ram controller */
cmp ramc1, #0
- ldrne tmp2, [ramc1, #AT91_DDRSDRC_LPR]
- strne tmp2, .saved_sam9_lpr1
- bicne tmp2, #AT91_DDRSDRC_LPCB
- orrne tmp2, #AT91_DDRSDRC_LPCB_SELF_REFRESH
+ beq ddr_no_2nd_ctrl
+
+ ldr tmp2, [ramc1, #AT91_DDRSDRC_MDR]
+ str tmp2, .saved_sam9_mdr1
+ bic tmp2, tmp2, #~AT91_DDRSDRC_MD
+ cmp tmp2, #AT91_DDRSDRC_MD_LOW_POWER_DDR
+ ldreq tmp2, [ramc1, #AT91_DDRSDRC_MDR]
+ biceq tmp2, tmp2, #AT91_DDRSDRC_MD
+ orreq tmp2, tmp2, #AT91_DDRSDRC_MD_DDR2
+ streq tmp2, [ramc1, #AT91_DDRSDRC_MDR]
+
+ ldr tmp2, [ramc1, #AT91_DDRSDRC_LPR]
+ str tmp2, .saved_sam9_lpr1
+ bic tmp2, #AT91_DDRSDRC_LPCB
+ orr tmp2, #AT91_DDRSDRC_LPCB_SELF_REFRESH

/* Enable DDRAM self-refresh mode */
+ str tmp2, [ramc1, #AT91_DDRSDRC_LPR]
+ddr_no_2nd_ctrl:
str tmp1, [sdramc, #AT91_DDRSDRC_LPR]
- strne tmp2, [ramc1, #AT91_DDRSDRC_LPR]

b sdr_sr_done

@@ -289,12 +311,17 @@ sdr_sr_done:
*/
cmp memctrl, #AT91_MEMCTRL_DDRSDR
bne sdr_en_restore
+ /* Restore MDR in case of LPDDR1 */
+ ldr tmp1, .saved_sam9_mdr
+ str tmp1, [sdramc, #AT91_DDRSDRC_MDR]
/* Restore LPR on AT91 with DDRAM */
ldr tmp1, .saved_sam9_lpr
str tmp1, [sdramc, #AT91_DDRSDRC_LPR]

/* if we use the second ram controller */
cmp ramc1, #0
+ ldrne tmp2, .saved_sam9_mdr1
+ strne tmp2, [ramc1, #AT91_DDRSDRC_MDR]
ldrne tmp2, .saved_sam9_lpr1
strne tmp2, [ramc1, #AT91_DDRSDRC_LPR]

@@ -328,5 +355,11 @@ ram_restored:
.saved_sam9_lpr1:
.word 0

+.saved_sam9_mdr:
+ .word 0
+
+.saved_sam9_mdr1:
+ .word 0
+
ENTRY(at91_slow_clock_sz)
.word .-at91_slow_clock
diff --git a/include/soc/at91/at91sam9_ddrsdr.h b/include/soc/at91/at91sam9_ddrsdr.h
index 0210797abf2e..cd2c18787833 100644
--- a/include/soc/at91/at91sam9_ddrsdr.h
+++ b/include/soc/at91/at91sam9_ddrsdr.h
@@ -92,7 +92,7 @@
#define AT91_DDRSDRC_UPD_MR (3 << 20) /* Update load mode register and extended mode register */

#define AT91_DDRSDRC_MDR 0x20 /* Memory Device Register */
-#define AT91_DDRSDRC_MD (3 << 0) /* Memory Device Type */
+#define AT91_DDRSDRC_MD (7 << 0) /* Memory Device Type */
#define AT91_DDRSDRC_MD_SDR 0
#define AT91_DDRSDRC_MD_LOW_POWER_SDR 1
#define AT91_DDRSDRC_MD_LOW_POWER_DDR 3
--
1.7.10.4


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