linux-kernel - Re: [PATCH v2 2/2] soc: mediatek: add a fixed wait for SRAM stable

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Date:   Mon, 23 Apr 2018 11:31:36 +0200
From:   Matthias Brugger <matthias.bgg@...il.com>
To:     sean.wang@...iatek.com, rjw@...ysocki.net, khilman@...libre.com
Cc:     ulf.hansson@...aro.org, linux-mediatek@...ts.infradead.org,
        linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Weiyi Lu <weiyi.lu@...iatek.com>
Subject: Re: [PATCH v2 2/2] soc: mediatek: add a fixed wait for SRAM stable



On 04/23/2018 10:36 AM, sean.wang@...iatek.com wrote:
> From: Sean Wang <sean.wang@...iatek.com>
> 
> MT7622_POWER_DOMAIN_WB doesn't send an ACK when its managed SRAM becomes
> stable, which is not like the behavior the other power domains should
> have. Therefore, it's necessary for such a power domain to have a fixed
> and well-predefined duration to wait until its managed SRAM can be allowed
> to access by all functions running on the top.
> 
> v1 -> v2:
>  - use MTK_SCPD_FWAIT_SRAM flag as an indication requiring force waiting.
> 
> Signed-off-by: Sean Wang <sean.wang@...iatek.com>
> Cc: Matthias Brugger <matthias.bgg@...il.com>
> Cc: Ulf Hansson <ulf.hansson@...aro.org>
> Cc: Weiyi Lu <weiyi.lu@...iatek.com>
> ---
>  drivers/soc/mediatek/mtk-scpsys.c | 24 ++++++++++++++++++------
>  1 file changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/soc/mediatek/mtk-scpsys.c b/drivers/soc/mediatek/mtk-scpsys.c
> index b1b45e4..d4f1a63 100644
> --- a/drivers/soc/mediatek/mtk-scpsys.c
> +++ b/drivers/soc/mediatek/mtk-scpsys.c
> @@ -32,6 +32,7 @@
>  #define MTK_POLL_TIMEOUT    (jiffies_to_usecs(HZ))
>  
>  #define MTK_SCPD_ACTIVE_WAKEUP		BIT(0)
> +#define MTK_SCPD_FWAIT_SRAM		BIT(1)
>  #define MTK_SCPD_CAPS(_scpd, _x)	((_scpd)->data->caps & (_x))
>  
>  #define SPM_VDE_PWR_CON			0x0210
> @@ -237,11 +238,22 @@ static int scpsys_power_on(struct generic_pm_domain *genpd)
>  	val &= ~scpd->data->sram_pdn_bits;
>  	writel(val, ctl_addr);
>  
> -	/* wait until SRAM_PDN_ACK all 0 */
> -	ret = readl_poll_timeout(ctl_addr, tmp, (tmp & pdn_ack) == 0,
> -				 MTK_POLL_DELAY_US, MTK_POLL_TIMEOUT);
> -	if (ret < 0)
> -		goto err_pwr_ack;
> +	/* Either wait until SRAM_PDN_ACK all 0 or have a force wait */
> +	if (!MTK_SCPD_CAPS(scpd, MTK_SCPD_FWAIT_SRAM)) {
> +		ret = readl_poll_timeout(ctl_addr, tmp, (tmp & pdn_ack) == 0,
> +					 MTK_POLL_DELAY_US, MTK_POLL_TIMEOUT);
> +		if (ret < 0)
> +			goto err_pwr_ack;
> +	} else {
> +		/*
> +		 * Currently, MTK_SCPD_FWAIT_SRAM is necessary only for
> +		 * MT7622_POWER_DOMAIN_WB and thus just a trivial setup is
> +		 * applied here. If there're more domains which need to force
> +		 * waiting for its own pre-defined value, the duration should
> +		 * be coded in the caps field.
> +		 */

I would say, if necessary in the future we can add a switch statement here.
Other then that the patches look good. If you are OK, I'll just delete the last
sentence when applying the patch.

Regards,
Matthias

> +		usleep_range(12000, 12100);
> +	};
>  
>  	if (scpd->data->bus_prot_mask) {
>  		ret = mtk_infracfg_clear_bus_protection(scp->infracfg,
> @@ -785,7 +797,7 @@ static const struct scp_domain_data scp_domain_data_mt7622[] = {
>  		.sram_pdn_ack_bits = 0,
>  		.clk_id = {CLK_NONE},
>  		.bus_prot_mask = MT7622_TOP_AXI_PROT_EN_WB,
> -		.caps = MTK_SCPD_ACTIVE_WAKEUP,
> +		.caps = MTK_SCPD_ACTIVE_WAKEUP | MTK_SCPD_FWAIT_SRAM,
>  	},
>  };
>  
>