linux-kernel - Re: [PATCH 16/16] soc: imx: gpcv2: remove waiting handshake in power up

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Message-ID: <e5a94506-7bd3-93b6-b331-1cf04672a459@oss.nxp.com>
Date:   Fri, 30 Apr 2021 15:14:34 +0800
From:   "Peng Fan (OSS)" <peng.fan@....nxp.com>
To:     Lucas Stach <l.stach@...gutronix.de>, robh+dt@...nel.org,
        shawnguo@...nel.org, s.hauer@...gutronix.de
Cc:     kernel@...gutronix.de, festevam@...il.com, linux-imx@....com,
        p.zabel@...gutronix.de, krzk@...nel.org, agx@...xcpu.org,
        marex@...x.de, andrew.smirnov@...il.com,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, ping.bai@....com,
        frieder.schrempf@...tron.de, aford173@...il.com, abel.vesa@....com,
        Peng Fan <peng.fan@....com>
Subject: Re: [PATCH 16/16] soc: imx: gpcv2: remove waiting handshake in power
 up



On 2021/4/29 22:34, Lucas Stach wrote:
> Am Donnerstag, dem 29.04.2021 um 15:30 +0800 schrieb Peng Fan (OSS):
>> From: Peng Fan <peng.fan@....com>
>>
>> i.MX8MM has blk ctl module, the handshake can only finish after setting
>> blk ctl. The blk ctl driver will set the bus clk bit and the handshake
>> will finish there. we just add a delay and suppose the handshake will
>> finish after that.
> 
> Instead of this patch, just drop patch 05/16 from this series. I think
> we should leave a comment in the code on why we aren't waiting for the
> handshake ack, as this is non-obvious from looking at the driver code.
> 
> Basically add a polished version of the commit log from this patch into
> the driver code.

After thinking more, for power down, we need wait handshake. For power 
up, we could ignore handshake, because BLK-CTL setting bus clk en
will auto trigger handshake.

For power down, the bus clk en already set, and we need wait, otherwise
we need add delay there.

So I would only drop the power up waiting and add some comments there.

Thanks,
Peng.

> 
> Regards,
> Lucas
> 
>> Signed-off-by: Peng Fan <peng.fan@....com>
>> ---
>>   drivers/soc/imx/gpcv2.c | 8 --------
>>   1 file changed, 8 deletions(-)
>>
>> diff --git a/drivers/soc/imx/gpcv2.c b/drivers/soc/imx/gpcv2.c
>> index 49dd137f6b94..04564017bfe9 100644
>> --- a/drivers/soc/imx/gpcv2.c
>> +++ b/drivers/soc/imx/gpcv2.c
>> @@ -251,14 +251,6 @@ static int imx_pgc_power_up(struct generic_pm_domain *genpd)
>>   		regmap_update_bits(domain->regmap, GPC_PU_PWRHSK,
>>   				   domain->bits.hskreq, domain->bits.hskreq);
>>   
>>
>>
>>
>> -		ret = regmap_read_poll_timeout(domain->regmap, GPC_PU_PWRHSK,
>> -					       reg_val,
>> -					       (reg_val & domain->bits.hskack),
>> -					       0, USEC_PER_MSEC);
>> -		if (ret) {
>> -			dev_err(domain->dev, "failed to power up ADB400\n");
>> -			goto out_clk_disable;
>> -		}
>>   	}
>>   
>>
>>
>>
>>   	/* Disable reset clocks for all devices in the domain */
> 
>