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

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Date:   Tue, 10 Jan 2017 17:18:21 +0100
From:   Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:     Wenyou Yang <wenyou.yang@...el.com>
Cc:     Russell King <linux@....linux.org.uk>,
        Nicolas Ferre <nicolas.ferre@...el.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-kernel@...r.kernel.org,
        Wenyou Yang <wenyou.yang@...rochip.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/3] ARM: at91: flush the L2 cache before entering cpu
 idle

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();
+		outer_disable();
+	}
+
 	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();
 }
 
 /* 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@...el.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