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authorNicolas Ferre <nicolas.ferre@microchip.com>2017-03-14 09:38:04 +0100
committerAlexandre Belloni <alexandre.belloni@free-electrons.com>2017-03-14 11:09:50 +0100
commit60b89f1928af80b546b5c3fd8714a62f6f4b8844 (patch)
tree4db4c0de974fcb1ebfcbf8869ef14e48353f9e95 /arch
parent9e10889a3177340dcda7d29c6d8fbd97247b007b (diff)
ARM: at91: pm: cpu_idle: switch DDR to power-down mode
On some DDR controllers, compatible with the sama5d3 one, the sequence to enter/exit/re-enter the self-refresh mode adds more constrains than what is currently written in the at91_idle driver. An actual access to the DDR chip is needed between exit and re-enter of this mode which is somehow difficult to implement. This sequence can completely hang the SoC. It is particularly experienced on parts which embed a L2 cache if the code run between IDLE calls fits in it... Moreover, as the intention is to enter and exit pretty rapidly from IDLE, the power-down mode is a good candidate. So now we use power-down instead of self-refresh. As we can simplify the code for sama5d3 compatible DDR controllers, we instantiate a new sama5d3_ddr_standby() function. Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com> Cc: <stable@vger.kernel.org> # v4.1+ Fixes: 017b5522d5e3 ("ARM: at91: Add new binding for sama5d3-ddramc") Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm/mach-at91/pm.c18
1 files changed, 17 insertions, 1 deletions
diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c
index 3d89b7905bd9..a277981f414d 100644
--- a/arch/arm/mach-at91/pm.c
+++ b/arch/arm/mach-at91/pm.c
@@ -289,6 +289,22 @@ static void at91_ddr_standby(void)
at91_ramc_write(1, AT91_DDRSDRC_LPR, saved_lpr1);
}
+static void sama5d3_ddr_standby(void)
+{
+ u32 lpr0;
+ u32 saved_lpr0;
+
+ saved_lpr0 = at91_ramc_read(0, AT91_DDRSDRC_LPR);
+ lpr0 = saved_lpr0 & ~AT91_DDRSDRC_LPCB;
+ lpr0 |= AT91_DDRSDRC_LPCB_POWER_DOWN;
+
+ at91_ramc_write(0, AT91_DDRSDRC_LPR, lpr0);
+
+ cpu_do_idle();
+
+ at91_ramc_write(0, AT91_DDRSDRC_LPR, saved_lpr0);
+}
+
/* We manage both DDRAM/SDRAM controllers, we need more than one value to
* remember.
*/
@@ -323,7 +339,7 @@ static const struct of_device_id const ramc_ids[] __initconst = {
{ .compatible = "atmel,at91rm9200-sdramc", .data = at91rm9200_standby },
{ .compatible = "atmel,at91sam9260-sdramc", .data = at91sam9_sdram_standby },
{ .compatible = "atmel,at91sam9g45-ddramc", .data = at91_ddr_standby },
- { .compatible = "atmel,sama5d3-ddramc", .data = at91_ddr_standby },
+ { .compatible = "atmel,sama5d3-ddramc", .data = sama5d3_ddr_standby },
{ /*sentinel*/ }
};