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Subject: Re: [PATCH v2 2/2] soc: mediatek: add a fixed wait for SRAM stable
To:     Sean Wang <sean.wang@mediatek.com>
Cc:     rjw@rjwysocki.net, khilman@baylibre.com, ulf.hansson@linaro.org,
        linux-mediatek@lists.infradead.org, linux-pm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Weiyi Lu <weiyi.lu@mediatek.com>
References: <2e16481e1477dfae0cfb24568d8111da81d92628.1524472331.git.sean.wang@mediatek.com>
 <0ef8e87ba7156e626d1a1a48388f222ce917099b.1524472331.git.sean.wang@mediatek.com>
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From:   Matthias Brugger <matthias.bgg@gmail.com>
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Message-ID: <0ec15c8a-ca90-26c3-1ea6-00bf0d48b62a@gmail.com>
Date:   Fri, 27 Apr 2018 11:46:14 +0200
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Hi Sean,

On 04/23/2018 11:39 AM, Sean Wang wrote:
> On Mon, 2018-04-23 at 11:31 +0200, Matthias Brugger wrote:
>>
>> On 04/23/2018 10:36 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.
>>>
>>> v1 -> v2:
>>>  - use MTK_SCPD_FWAIT_SRAM flag as an indication requiring force waiting.
>>>
>>> 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 | 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)) {

After having another look on the patch, could you change the order of the if:
So that we check for the existence of the MTK_SCPD_FWAIT_SRAM and sleep and in
the else branch we to the readl_poll_timeout.

I think in the future this will make the code easier to understand as you can
easily oversee the '!' negation in the if.

Regards,
Matthias


>>> +		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.
>>
> 
> yes, it's okay for me. 
> 
>> 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,
>>>  	},
>>>  };
>>>  
>>>
> 
>