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Subject: Re: [PATCH v1 5/7] soc: mediatek: add a fixed wait for SRAM stable
To:     sean.wang@mediatek.com, robh+dt@kernel.org, mark.rutland@arm.com,
        marcel@holtmann.org, johan.hedberg@gmail.com
Cc:     devicetree@vger.kernel.org, linux-bluetooth@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Weiyi Lu <weiyi.lu@mediatek.com>
References: <cover.1522736996.git.sean.wang@mediatek.com>
 <0fc10b2498c6dbe20141831c722c32cc74330d3d.1522736996.git.sean.wang@mediatek.com>
From:   Matthias Brugger <matthias.bgg@gmail.com>
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Message-ID: <5f2530a0-aee2-39fe-eb5c-56cd4a68c9db@gmail.com>
Date:   Thu, 19 Apr 2018 12:33:37 +0200
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On 04/03/2018 09:15 AM, sean.wang@mediatek.com wrote:
> From: Sean Wang <sean.wang@mediatek.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.
> 
> Signed-off-by: Sean Wang <sean.wang@mediatek.com>
> Cc: Matthias Brugger <matthias.bgg@gmail.com>
> Cc: Ulf Hansson <ulf.hansson@linaro.org>
> Cc: Weiyi Lu <weiyi.lu@mediatek.com>
> ---
>  drivers/soc/mediatek/mtk-scpsys.c | 17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/soc/mediatek/mtk-scpsys.c b/drivers/soc/mediatek/mtk-scpsys.c
> index f9b7248..19aceb8 100644
> --- a/drivers/soc/mediatek/mtk-scpsys.c
> +++ b/drivers/soc/mediatek/mtk-scpsys.c
> @@ -121,6 +121,7 @@ struct scp_domain_data {
>  	u32 bus_prot_mask;
>  	enum clk_id clk_id[MAX_CLKS];
>  	bool active_wakeup;
> +	u32 us_sram_fwait;

Before adding more and more fields to scp_domain_data which get checked in if's,
I'd prefer to add a caps field used for bus_prot_mask, active_wakeup in a first
patch and add the cap FORCE_WAIT in a second patch.

Can you help to implement this Sean, or shall I give it a try?

Regards,
Matthias

>  };
>  
>  struct scp;
> @@ -234,11 +235,16 @@ 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 (!scpd->data->us_sram_fwait) {
> +		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 {
> +		usleep_range(scpd->data->us_sram_fwait,
> +			     scpd->data->us_sram_fwait + 100);
> +	};
>  
>  	if (scpd->data->bus_prot_mask) {
>  		ret = mtk_infracfg_clear_bus_protection(scp->infracfg,
> @@ -783,6 +789,7 @@ static const struct scp_domain_data scp_domain_data_mt7622[] = {
>  		.clk_id = {CLK_NONE},
>  		.bus_prot_mask = MT7622_TOP_AXI_PROT_EN_WB,
>  		.active_wakeup = true,
> +		.us_sram_fwait = 12000,
>  	},
>  };
>  
>