* [PATCH] ARM: at91: pm: cpu_idle: switch DDR to power-down mode
@ 2017-03-13 17:14 ` Nicolas Ferre
0 siblings, 0 replies; 6+ messages in thread
From: Nicolas Ferre @ 2017-03-13 17:14 UTC (permalink / raw)
To: Alexandre Belloni, Boris BREZILLON, Wenyou Yang, linux-arm-kernel
Cc: linux-kernel, Nicolas Ferre
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 funciton for sama5d3 compatible DDR controllers,
we instanciate a new sama5d3_ddr_standby() function.
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
---
arch/arm/mach-at91/pm.c | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c
index 3d89b7905bd9..63e7df8ec815 100644
--- a/arch/arm/mach-at91/pm.c
+++ b/arch/arm/mach-at91/pm.c
@@ -289,6 +289,23 @@ 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;
+
+ /* self-refresh mode now */
+ 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 +340,7 @@ 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*/ }
};
--
2.9.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH] ARM: at91: pm: cpu_idle: switch DDR to power-down mode
@ 2017-03-13 17:14 ` Nicolas Ferre
0 siblings, 0 replies; 6+ messages in thread
From: Nicolas Ferre @ 2017-03-13 17:14 UTC (permalink / raw)
To: linux-arm-kernel
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 funciton for sama5d3 compatible DDR controllers,
we instanciate a new sama5d3_ddr_standby() function.
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
---
arch/arm/mach-at91/pm.c | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c
index 3d89b7905bd9..63e7df8ec815 100644
--- a/arch/arm/mach-at91/pm.c
+++ b/arch/arm/mach-at91/pm.c
@@ -289,6 +289,23 @@ 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;
+
+ /* self-refresh mode now */
+ 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 +340,7 @@ 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*/ }
};
--
2.9.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] ARM: at91: pm: cpu_idle: switch DDR to power-down mode
2017-03-13 17:14 ` Nicolas Ferre
@ 2017-03-13 21:07 ` Alexandre Belloni
-1 siblings, 0 replies; 6+ messages in thread
From: Alexandre Belloni @ 2017-03-13 21:07 UTC (permalink / raw)
To: Nicolas Ferre
Cc: Boris BREZILLON, Wenyou Yang, linux-arm-kernel, linux-kernel
On 13/03/2017 at 18:14:50 +0100, Nicolas Ferre wrote:
> 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 funciton for sama5d3 compatible DDR controllers,
typo ^
> we instanciate a new sama5d3_ddr_standby() function.
>
> Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
> ---
> arch/arm/mach-at91/pm.c | 19 ++++++++++++++++++-
> 1 file changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c
> index 3d89b7905bd9..63e7df8ec815 100644
> --- a/arch/arm/mach-at91/pm.c
> +++ b/arch/arm/mach-at91/pm.c
> @@ -289,6 +289,23 @@ 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;
> +
> + /* self-refresh mode now */
So this is not self refresh anymore
--
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] ARM: at91: pm: cpu_idle: switch DDR to power-down mode
@ 2017-03-13 21:07 ` Alexandre Belloni
0 siblings, 0 replies; 6+ messages in thread
From: Alexandre Belloni @ 2017-03-13 21:07 UTC (permalink / raw)
To: linux-arm-kernel
On 13/03/2017 at 18:14:50 +0100, Nicolas Ferre wrote:
> 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 funciton for sama5d3 compatible DDR controllers,
typo ^
> we instanciate a new sama5d3_ddr_standby() function.
>
> Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
> ---
> arch/arm/mach-at91/pm.c | 19 ++++++++++++++++++-
> 1 file changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c
> index 3d89b7905bd9..63e7df8ec815 100644
> --- a/arch/arm/mach-at91/pm.c
> +++ b/arch/arm/mach-at91/pm.c
> @@ -289,6 +289,23 @@ 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;
> +
> + /* self-refresh mode now */
So this is not self refresh anymore
--
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] ARM: at91: pm: cpu_idle: switch DDR to power-down mode
2017-03-13 21:07 ` Alexandre Belloni
@ 2017-03-14 8:21 ` Nicolas Ferre
-1 siblings, 0 replies; 6+ messages in thread
From: Nicolas Ferre @ 2017-03-14 8:21 UTC (permalink / raw)
To: Alexandre Belloni
Cc: Boris BREZILLON, Wenyou Yang, linux-arm-kernel, linux-kernel
Le 13/03/2017 à 22:07, Alexandre Belloni a écrit :
> On 13/03/2017 at 18:14:50 +0100, Nicolas Ferre wrote:
>> 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 funciton for sama5d3 compatible DDR controllers,
> typo ^
>
>> we instanciate a new sama5d3_ddr_standby() function.
And here ^ also: I rewrite a v2 now.
>> Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
>> ---
>> arch/arm/mach-at91/pm.c | 19 ++++++++++++++++++-
>> 1 file changed, 18 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c
>> index 3d89b7905bd9..63e7df8ec815 100644
>> --- a/arch/arm/mach-at91/pm.c
>> +++ b/arch/arm/mach-at91/pm.c
>> @@ -289,6 +289,23 @@ 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;
>> +
>> + /* self-refresh mode now */
>
> So this is not self refresh anymore
True, and useless comment in this case: so I simply remove it!
Sorry for the noise.
Regards,
--
Nicolas Ferre
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] ARM: at91: pm: cpu_idle: switch DDR to power-down mode
@ 2017-03-14 8:21 ` Nicolas Ferre
0 siblings, 0 replies; 6+ messages in thread
From: Nicolas Ferre @ 2017-03-14 8:21 UTC (permalink / raw)
To: linux-arm-kernel
Le 13/03/2017 ? 22:07, Alexandre Belloni a ?crit :
> On 13/03/2017 at 18:14:50 +0100, Nicolas Ferre wrote:
>> 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 funciton for sama5d3 compatible DDR controllers,
> typo ^
>
>> we instanciate a new sama5d3_ddr_standby() function.
And here ^ also: I rewrite a v2 now.
>> Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
>> ---
>> arch/arm/mach-at91/pm.c | 19 ++++++++++++++++++-
>> 1 file changed, 18 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c
>> index 3d89b7905bd9..63e7df8ec815 100644
>> --- a/arch/arm/mach-at91/pm.c
>> +++ b/arch/arm/mach-at91/pm.c
>> @@ -289,6 +289,23 @@ 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;
>> +
>> + /* self-refresh mode now */
>
> So this is not self refresh anymore
True, and useless comment in this case: so I simply remove it!
Sorry for the noise.
Regards,
--
Nicolas Ferre
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2017-03-14 8:21 UTC | newest]
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2017-03-13 17:14 [PATCH] ARM: at91: pm: cpu_idle: switch DDR to power-down mode Nicolas Ferre
2017-03-13 17:14 ` Nicolas Ferre
2017-03-13 21:07 ` Alexandre Belloni
2017-03-13 21:07 ` Alexandre Belloni
2017-03-14 8:21 ` Nicolas Ferre
2017-03-14 8:21 ` Nicolas Ferre
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