linux-kernel - Re: [PATCH v5 1/3] phy: Power on PHY before start Serdes configuration

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Date:   Fri, 25 May 2018 09:32:34 +0800
From:   cang@...eaurora.org
To:     Vivek Gautam <vivek.gautam@...eaurora.org>
Cc:     subhashj@...eaurora.org, asutoshd@...eaurora.org,
        mgautam@...eaurora.org, kishon@...com, robh+dt@...nel.org,
        mark.rutland@....com, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v5 1/3] phy: Power on PHY before start Serdes
 configuration

On 2018-05-24 16:17, Vivek Gautam wrote:
> Hi Can,
> 
> 
> On 5/23/2018 9:17 AM, Can Guo wrote:
>> PHYs should be powered on before register configuration starts.
>> 
>> Signed-off-by: Can Guo <cang@...eaurora.org>
>> ---
> 
> Thanks for fixing this.
> 
>>   drivers/phy/qualcomm/phy-qcom-qmp.c | 6 ++++++
>>   1 file changed, 6 insertions(+)
>> 
>> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp.c 
>> b/drivers/phy/qualcomm/phy-qcom-qmp.c
>> index 97ef942..9bfdba1 100644
>> --- a/drivers/phy/qualcomm/phy-qcom-qmp.c
>> +++ b/drivers/phy/qualcomm/phy-qcom-qmp.c
>> @@ -1000,6 +1000,12 @@ static int qcom_qmp_phy_com_init(struct 
>> qcom_qmp *qmp)
>>   			     SW_USB3PHY_RESET_MUX | SW_USB3PHY_RESET);
>>   	}
>>   +	/*
>> +	 * Pull out PHY from POWER DOWN state.
>> +	 * This is active low enable signal to power-down PHY.
>> +	 */
>> +	qphy_setbits(pcs, QPHY_POWER_DOWN_CONTROL, cfg->pwrdn_ctrl);
>> +
> 
> Thanks. This is in sync with the requirements of USB and UFS phys
> across platforms
> using this qmp phy driver, viz. 8996 and 845.
> However, as discussed with you offline the PCIe phy has different 
> requirement.
> PCIe phy on 8996 doesn't need the QPHY_POWER_DOWN_CONTROL (pcs level 
> power down)
> before configuring the phys. Rather COM_POWER_DOWN_CONTROL is enough.
> It needs the QPHY_POWER_DOWN_CONTROL after programming the
> serdes, tx, rx, and pcs blocks, and right before doing SW_RESET, and
> START_CONTROL.
> 
> So we should just do the above QPHY_POWER_DOWN_CONTROL in
> qcom_qmp_phy_com_init() only for non-PCIe phys at the moment, and
> skip the QPHY_POWER_DOWN_CONTROL in qcom_qmp_phy_init()
> for these non-PCIe phys.
> 
> Thanks
> Vivek
> 

Sure Vivek, I shall make the change per we talked.

Thanks
Can

>>   	/* Serdes configuration */
>>   	qcom_qmp_phy_configure(serdes, cfg->regs, cfg->serdes_tbl,
>>   			       cfg->serdes_tbl_num);