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

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Message-ID: <dd6b1e3d-e894-e40f-452a-2dec2421b1c7@codeaurora.org>
Date:   Thu, 24 May 2018 13:47:58 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Can Guo <cang@...eaurora.org>, subhashj@...eaurora.org,
        asutoshd@...eaurora.org, mgautam@...eaurora.org, kishon@...com,
        robh+dt@...nel.org, mark.rutland@....com
Cc:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v5 1/3] phy: Power on PHY before start Serdes
 configuration

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

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