linux-kernel - Re: [PATCH RESEND] pm: at91: Workaround DDRSDRC self-refresh bug with LPDDR1 memories

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Message-ID: <54B69DAB.8010303@atmel.com>
Date:	Wed, 14 Jan 2015 17:47:39 +0100
From:	Nicolas Ferre <nicolas.ferre@...el.com>
To:	Peter Rosin <peda@...ator.liu.se>,
	<linux-arm-kernel@...ts.infradead.org>,
	"Yang, Wenyou" <Wenyou.Yang@...el.com>
CC:	Peter Rosin <peda@...ntia.se>, Andrew Victor <linux@...im.org.za>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Russell King <linux@....linux.org.uk>,
	<linux-kernel@...r.kernel.org>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Boris BREZILLON <boris.brezillon@...e-electrons.com>
Subject: Re: [PATCH RESEND] pm: at91: Workaround DDRSDRC self-refresh bug
 with LPDDR1 memories

Le 14/01/2015 14:20, Peter Rosin a écrit :
> From: Peter Rosin <peda@...ntia.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@...ntia.se>

I've just verified your code and the scope of this issue and your
implementation makes perfect sense.

Acked-by: Nicolas Ferre <nicolas.ferre@...el.com>

Peter,
Thanks for your patch. You will probably see it appearing in 3.20 or 3.21.

Wenyou,
Can you please integrate the patch from Peter in your current rework of
the PM routines (keeping his authorship of course)?
Please tell me if I can help with this.

Best regards,


> ---
>  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
> 


-- 
Nicolas Ferre
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