Re: [PATCH 1/3] ARM: at91: flush the L2 cache before entering cpu idle

[Jean-Jacques Hiblot <jjhiblot@gmail.com>]

2017-01-10 17:18 GMT+01:00 Alexandre Belloni
<alexandre.belloni@free-electrons.com>:
> I though a bit more about it, and I don't really like the new compatible
> string. I don't feel this should be necessary.
>
> What about the following:
>
> diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c
> index b4332b727e9c..0333aca63e44 100644
> --- a/arch/arm/mach-at91/pm.c
> +++ b/arch/arm/mach-at91/pm.c
> @@ -53,6 +53,7 @@ extern void at91_pinctrl_gpio_resume(void);
>  static struct {
>         unsigned long uhp_udp_mask;
>         int memctrl;
> +       bool has_l2_cache;
>  } at91_pm_data;
>
>  void __iomem *at91_ramc_base[2];
> @@ -267,6 +268,11 @@ static void at91_ddr_standby(void)
>         u32 lpr0, lpr1 = 0;
>         u32 saved_lpr0, saved_lpr1 = 0;
>

> +       if (at91_pm_data.has_l2_cache) {
> +               flush_cache_all();
what is the point of calling flush_cache_all() here ? Do we really
care that dirty data in L1 is written to DDR ? I may be missing
something but to me it's just extra latency.
> +               outer_disable();
It seems to me that if there's no L2 cache, then outer_disable()  is a
no-op. It could be called unconditionally.
> +       }
> +
>         if (at91_ramc_base[1]) {
>                 saved_lpr1 = at91_ramc_read(1, AT91_DDRSDRC_LPR);
>                 lpr1 = saved_lpr1 & ~AT91_DDRSDRC_LPCB;
> @@ -287,6 +293,9 @@ static void at91_ddr_standby(void)
>         at91_ramc_write(0, AT91_DDRSDRC_LPR, saved_lpr0);
>         if (at91_ramc_base[1])
>                 at91_ramc_write(1, AT91_DDRSDRC_LPR, saved_lpr1);
> +
> +       if (at91_pm_data.has_l2_cache)
> +               outer_resume();

same remark as for outer_disable()

Jean-Jacques

>  }
>
>  /* We manage both DDRAM/SDRAM controllers, we need more than one value
>  * to
> @@ -353,6 +362,11 @@ static __init void at91_dt_ramc(void)
>                 return;
>         }
>
> +       np = of_find_compatible_node(NULL, NULL, "arm,pl310-cache");
> +       if (np)
> +               at91_pm_data.has_l2_cache = true;
> +       of_node_put(np);
> +
>         at91_pm_set_standby(standby);
>  }
>
>
> This has the following benefits:
>  - everybody will have the fix, regardless of whether the dtb is updated
>  - has_l2_cache can be used later in at91_pm_suspend instead of calling
>    it unconditionnaly (I'll send a patch)
>
>
> On 06/01/2017 at 14:59:45 +0800, Wenyou Yang wrote :
>> For the SoCs such as SAMA5D2 and SAMA5D4 which have L2 cache,
>> flush the L2 cache first before entering the cpu idle.
>>
>> Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
>> ---
>>
>>  arch/arm/mach-at91/pm.c       | 19 +++++++++++++++++++
>>  drivers/memory/atmel-sdramc.c |  1 +
>>  2 files changed, 20 insertions(+)
>>
>> diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c
>> index b4332b727e9c..1a60dede1a01 100644
>> --- a/arch/arm/mach-at91/pm.c
>> +++ b/arch/arm/mach-at91/pm.c
>> @@ -289,6 +289,24 @@ static void at91_ddr_standby(void)
>>               at91_ramc_write(1, AT91_DDRSDRC_LPR, saved_lpr1);
>>  }
>>
>> +static void at91_ddr_cache_standby(void)
>> +{
>> +     u32 saved_lpr;
>> +
>> +     flush_cache_all();
>> +     outer_disable();
>> +
>> +     saved_lpr = at91_ramc_read(0, AT91_DDRSDRC_LPR);
>> +     at91_ramc_write(0, AT91_DDRSDRC_LPR, (saved_lpr &
>> +                     (~AT91_DDRSDRC_LPCB)) | AT91_DDRSDRC_LPCB_SELF_REFRESH);
>> +
>> +     cpu_do_idle();
>> +
>> +     at91_ramc_write(0, AT91_DDRSDRC_LPR, saved_lpr);
>> +
>> +     outer_resume();
>> +}
>> +
>>  /* We manage both DDRAM/SDRAM controllers, we need more than one value to
>>   * remember.
>>   */
>> @@ -324,6 +342,7 @@ static const struct of_device_id const ramc_ids[] __initconst = {
>>       { .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,sama5d4-ddramc", .data = at91_ddr_cache_standby },
>>       { /*sentinel*/ }
>>  };
>>
>> diff --git a/drivers/memory/atmel-sdramc.c b/drivers/memory/atmel-sdramc.c
>> index b418b39af180..7e5c5c6c1348 100644
>> --- a/drivers/memory/atmel-sdramc.c
>> +++ b/drivers/memory/atmel-sdramc.c
>> @@ -48,6 +48,7 @@ static const struct of_device_id atmel_ramc_of_match[] = {
>>       { .compatible = "atmel,at91sam9260-sdramc", .data = &at91rm9200_caps, },
>>       { .compatible = "atmel,at91sam9g45-ddramc", .data = &at91sam9g45_caps, },
>>       { .compatible = "atmel,sama5d3-ddramc", .data = &sama5d3_caps, },
>> +     { .compatible = "atmel,sama5d4-ddramc", .data = &sama5d3_caps, },
>>       {},
>>  };
>>
>> --
>> 2.11.0
>>
>
> --
> Alexandre Belloni, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com
>
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