Re: [PATCH 08/13] phy: qcom-qmp-pcie: drop power-down delay config

[Dmitry Baryshkov]

On 11/10/2022 16:14, Johan Hovold wrote:
> The power-down delay was included in the first version of the QMP driver
> as an optional delay after powering on the PHY (using
> POWER_DOWN_CONTROL) and just before starting it. Later changes modified
> this sequence by powering on before initialising the PHY, but the
> optional delay stayed where it was (i.e. before starting the PHY).
>
> The vendor driver does not use a delay before starting the PHY and this
> is likely not needed on any platform unless there is a corresponding
> delay in the vendor kernel init sequence tables (i.e. in devicetree).
>
> Let's keep the delay for now, but drop the redundant delay period
> configuration while increasing the unnecessarily low timer slack
> somewhat.

Actually, the vendor driver does this 995..1005 sleep. But contrary to 
our driver it does that after programming whole PHY init sequence, which 
includes SW_RESET / START_CTL, but before programming the pipe clocks.

I think we can either drop this delay completely, or move it before 
read_poll_timeout().

> Signed-off-by: Johan Hovold <johan+linaro@xxxxxxxxxx>
> ---
>   drivers/phy/qualcomm/phy-qcom-qmp-pcie.c | 27 +-----------------------
>   1 file changed, 1 insertion(+), 26 deletions(-)
>
> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> index fa8bc6aeedf1..315de484f875 100644
> --- a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> +++ b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> @@ -1362,9 +1362,6 @@ struct qmp_phy_cfg {
>   
>   	/* true, if PHY needs delay after POWER_DOWN */
>   	bool has_pwrdn_delay;
> -	/* power_down delay in usec */
> -	int pwrdn_delay_min;
> -	int pwrdn_delay_max;
>   
>   	/* QMP PHY pipe clock interface rate */
>   	unsigned long pipe_clock_rate;
> @@ -1500,8 +1497,6 @@ static const struct qmp_phy_cfg ipq8074_pciephy_cfg = {
>   	.phy_status		= PHYSTATUS,
>   
>   	.has_pwrdn_delay	= true,
> -	.pwrdn_delay_min	= 995,		/* us */
> -	.pwrdn_delay_max	= 1005,		/* us */
>   };
>   
>   static const struct qmp_phy_cfg ipq8074_pciephy_gen3_cfg = {
> @@ -1529,8 +1524,6 @@ static const struct qmp_phy_cfg ipq8074_pciephy_gen3_cfg = {
>   	.pwrdn_ctrl		= SW_PWRDN | REFCLK_DRV_DSBL,
>   
>   	.has_pwrdn_delay	= true,
> -	.pwrdn_delay_min	= 995,		/* us */
> -	.pwrdn_delay_max	= 1005,		/* us */
>   
>   	.pipe_clock_rate	= 250000000,
>   };
> @@ -1562,8 +1555,6 @@ static const struct qmp_phy_cfg ipq6018_pciephy_cfg = {
>   	.pwrdn_ctrl		= SW_PWRDN | REFCLK_DRV_DSBL,
>   
>   	.has_pwrdn_delay	= true,
> -	.pwrdn_delay_min	= 995,		/* us */
> -	.pwrdn_delay_max	= 1005,		/* us */
>   };
>   
>   static const struct qmp_phy_cfg sdm845_qmp_pciephy_cfg = {
> @@ -1594,8 +1585,6 @@ static const struct qmp_phy_cfg sdm845_qmp_pciephy_cfg = {
>   	.phy_status		= PHYSTATUS,
>   
>   	.has_pwrdn_delay	= true,
> -	.pwrdn_delay_min	= 995,		/* us */
> -	.pwrdn_delay_max	= 1005,		/* us */
>   };
>   
>   static const struct qmp_phy_cfg sdm845_qhp_pciephy_cfg = {
> @@ -1624,8 +1613,6 @@ static const struct qmp_phy_cfg sdm845_qhp_pciephy_cfg = {
>   	.phy_status		= PHYSTATUS,
>   
>   	.has_pwrdn_delay	= true,
> -	.pwrdn_delay_min	= 995,		/* us */
> -	.pwrdn_delay_max	= 1005,		/* us */
>   };
>   
>   static const struct qmp_phy_cfg sm8250_qmp_gen3x1_pciephy_cfg = {
> @@ -1666,8 +1653,6 @@ static const struct qmp_phy_cfg sm8250_qmp_gen3x1_pciephy_cfg = {
>   	.phy_status		= PHYSTATUS,
>   
>   	.has_pwrdn_delay	= true,
> -	.pwrdn_delay_min	= 995,		/* us */
> -	.pwrdn_delay_max	= 1005,		/* us */
>   };
>   
>   static const struct qmp_phy_cfg sm8250_qmp_gen3x2_pciephy_cfg = {
> @@ -1708,8 +1693,6 @@ static const struct qmp_phy_cfg sm8250_qmp_gen3x2_pciephy_cfg = {
>   	.phy_status		= PHYSTATUS,
>   
>   	.has_pwrdn_delay	= true,
> -	.pwrdn_delay_min	= 995,		/* us */
> -	.pwrdn_delay_max	= 1005,		/* us */
>   };
>   
>   static const struct qmp_phy_cfg msm8998_pciephy_cfg = {
> @@ -1765,8 +1748,6 @@ static const struct qmp_phy_cfg sc8180x_pciephy_cfg = {
>   	.pwrdn_ctrl		= SW_PWRDN | REFCLK_DRV_DSBL,
>   
>   	.has_pwrdn_delay	= true,
> -	.pwrdn_delay_min	= 995,		/* us */
> -	.pwrdn_delay_max	= 1005,		/* us */
>   };
>   
>   static const struct qmp_phy_cfg sdx55_qmp_pciephy_cfg = {
> @@ -1797,8 +1778,6 @@ static const struct qmp_phy_cfg sdx55_qmp_pciephy_cfg = {
>   	.phy_status		= PHYSTATUS_4_20,
>   
>   	.has_pwrdn_delay	= true,
> -	.pwrdn_delay_min	= 995,		/* us */
> -	.pwrdn_delay_max	= 1005,		/* us */
>   };
>   
>   static const struct qmp_phy_cfg sm8450_qmp_gen3x1_pciephy_cfg = {
> @@ -1829,8 +1808,6 @@ static const struct qmp_phy_cfg sm8450_qmp_gen3x1_pciephy_cfg = {
>   	.phy_status		= PHYSTATUS,
>   
>   	.has_pwrdn_delay	= true,
> -	.pwrdn_delay_min	= 995,		/* us */
> -	.pwrdn_delay_max	= 1005,		/* us */
>   };
>   
>   static const struct qmp_phy_cfg sm8450_qmp_gen4x2_pciephy_cfg = {
> @@ -1876,8 +1853,6 @@ static const struct qmp_phy_cfg sm8450_qmp_gen4x2_pciephy_cfg = {
>   	.phy_status		= PHYSTATUS_4_20,
>   
>   	.has_pwrdn_delay	= true,
> -	.pwrdn_delay_min	= 995,		/* us */
> -	.pwrdn_delay_max	= 1005,		/* us */
>   };
>   
>   static void qmp_pcie_configure_lane(void __iomem *base,
> @@ -2037,7 +2012,7 @@ static int qmp_pcie_power_on(struct phy *phy)
>   	qmp_pcie_pcs_init(qphy, mode_tables);
>   
>   	if (cfg->has_pwrdn_delay)
> -		usleep_range(cfg->pwrdn_delay_min, cfg->pwrdn_delay_max);
> +		usleep_range(1000, 1200);
>   
>   	/* Pull PHY out of reset state */
>   	qphy_clrbits(pcs, cfg->regs[QPHY_SW_RESET], SW_RESET);

--
With best wishes
Dmitry