PCI: qcom: Add link retention support

[PATCH 1/5] phy: qcom: qmp-pcie: Skip PHY reset if already up

Posted by Krishna Chaitanya Chundru 1 month ago

If the bootloader has already powered up the PCIe PHY, doing a full
reset and waiting for it to come up again slows down boot time.

Add a check for PHY status and skip the reset steps when the PHY is
already active. In this case, only enable the required resources during
power-on. This works alongside the existing logic that skips the init
sequence.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
 drivers/phy/qualcomm/phy-qcom-qmp-pcie.c | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
index 86b1b7e2da86a8675e3e48e90b782afb21cafd77..c93e613cf80b2612f0f225fa2125f78dbec1a33f 100644
--- a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
+++ b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
@@ -3153,6 +3153,7 @@ struct qmp_pcie {
 	const struct qmp_phy_cfg *cfg;
 	bool tcsr_4ln_config;
 	bool skip_init;
+	bool skip_reset;
 
 	void __iomem *serdes;
 	void __iomem *pcs;
@@ -4537,6 +4538,9 @@ static int qmp_pcie_init(struct phy *phy)
 		qphy_checkbits(pcs, cfg->regs[QPHY_START_CTRL], SERDES_START | PCS_START) &&
 		qphy_checkbits(pcs, cfg->regs[QPHY_PCS_POWER_DOWN_CONTROL], cfg->pwrdn_ctrl);
 
+	qmp->skip_reset = qmp->skip_init && !qphy_checkbits(pcs, cfg->regs[QPHY_PCS_STATUS],
+							    cfg->phy_status);
+
 	if (!qmp->skip_init && !cfg->tbls.serdes_num) {
 		dev_err(qmp->dev, "Init sequence not available\n");
 		return -ENODATA;
@@ -4560,13 +4564,15 @@ static int qmp_pcie_init(struct phy *phy)
 		}
 	}
 
-	ret = reset_control_assert(qmp->nocsr_reset);
-	if (ret) {
-		dev_err(qmp->dev, "no-csr reset assert failed\n");
-		goto err_assert_reset;
-	}
+	if (!qmp->skip_reset) {
+		ret = reset_control_assert(qmp->nocsr_reset);
+		if (ret) {
+			dev_err(qmp->dev, "no-csr reset assert failed\n");
+			goto err_assert_reset;
+		}
 
-	usleep_range(200, 300);
+		usleep_range(200, 300);
+	}
 
 	if (!qmp->skip_init) {
 		ret = reset_control_bulk_deassert(cfg->num_resets, qmp->resets);
@@ -4641,10 +4647,12 @@ static int qmp_pcie_power_on(struct phy *phy)
 	if (ret)
 		return ret;
 
-	ret = reset_control_deassert(qmp->nocsr_reset);
-	if (ret) {
-		dev_err(qmp->dev, "no-csr reset deassert failed\n");
-		goto err_disable_pipe_clk;
+	if (!qmp->skip_reset) {
+		ret = reset_control_deassert(qmp->nocsr_reset);
+		if (ret) {
+			dev_err(qmp->dev, "no-csr reset deassert failed\n");
+			goto err_disable_pipe_clk;
+		}
 	}
 
 	if (qmp->skip_init)

-- 
2.34.1

Re: [PATCH 1/5] phy: qcom: qmp-pcie: Skip PHY reset if already up

Posted by Dmitry Baryshkov 1 month ago

On Fri, Jan 09, 2026 at 12:51:06PM +0530, Krishna Chaitanya Chundru wrote:
> If the bootloader has already powered up the PCIe PHY, doing a full
> reset and waiting for it to come up again slows down boot time.

How big is the delay caused by it?

> 
> Add a check for PHY status and skip the reset steps when the PHY is
> already active. In this case, only enable the required resources during
> power-on. This works alongside the existing logic that skips the init
> sequence.

Can we end up in a state where the bootloader has mis-setup the link? Or
the link going bad because of any glitch during the bootup?

> 
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
> ---
>  drivers/phy/qualcomm/phy-qcom-qmp-pcie.c | 28 ++++++++++++++++++----------
>  1 file changed, 18 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> index 86b1b7e2da86a8675e3e48e90b782afb21cafd77..c93e613cf80b2612f0f225fa2125f78dbec1a33f 100644
> --- a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> +++ b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> @@ -3153,6 +3153,7 @@ struct qmp_pcie {
>  	const struct qmp_phy_cfg *cfg;
>  	bool tcsr_4ln_config;
>  	bool skip_init;
> +	bool skip_reset;
>  
>  	void __iomem *serdes;
>  	void __iomem *pcs;
> @@ -4537,6 +4538,9 @@ static int qmp_pcie_init(struct phy *phy)
>  		qphy_checkbits(pcs, cfg->regs[QPHY_START_CTRL], SERDES_START | PCS_START) &&
>  		qphy_checkbits(pcs, cfg->regs[QPHY_PCS_POWER_DOWN_CONTROL], cfg->pwrdn_ctrl);
>  
> +	qmp->skip_reset = qmp->skip_init && !qphy_checkbits(pcs, cfg->regs[QPHY_PCS_STATUS],

It is definitely not a long-term state, there is no need to store it in
qmp_pcie struct.

> +							    cfg->phy_status);
> +
>  	if (!qmp->skip_init && !cfg->tbls.serdes_num) {
>  		dev_err(qmp->dev, "Init sequence not available\n");
>  		return -ENODATA;
> @@ -4560,13 +4564,15 @@ static int qmp_pcie_init(struct phy *phy)
>  		}
>  	}
>  
> -	ret = reset_control_assert(qmp->nocsr_reset);
> -	if (ret) {
> -		dev_err(qmp->dev, "no-csr reset assert failed\n");
> -		goto err_assert_reset;
> -	}
> +	if (!qmp->skip_reset) {
> +		ret = reset_control_assert(qmp->nocsr_reset);
> +		if (ret) {
> +			dev_err(qmp->dev, "no-csr reset assert failed\n");
> +			goto err_assert_reset;
> +		}
>  
> -	usleep_range(200, 300);
> +		usleep_range(200, 300);
> +	}
>  
>  	if (!qmp->skip_init) {
>  		ret = reset_control_bulk_deassert(cfg->num_resets, qmp->resets);
> @@ -4641,10 +4647,12 @@ static int qmp_pcie_power_on(struct phy *phy)
>  	if (ret)
>  		return ret;
>  
> -	ret = reset_control_deassert(qmp->nocsr_reset);
> -	if (ret) {
> -		dev_err(qmp->dev, "no-csr reset deassert failed\n");
> -		goto err_disable_pipe_clk;
> +	if (!qmp->skip_reset) {
> +		ret = reset_control_deassert(qmp->nocsr_reset);
> +		if (ret) {
> +			dev_err(qmp->dev, "no-csr reset deassert failed\n");
> +			goto err_disable_pipe_clk;
> +		}
>  	}
>  
>  	if (qmp->skip_init)
> 
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry

Re: [PATCH 1/5] phy: qcom: qmp-pcie: Skip PHY reset if already up

Posted by Neil Armstrong 1 month ago

On 1/9/26 14:08, Dmitry Baryshkov wrote:
> On Fri, Jan 09, 2026 at 12:51:06PM +0530, Krishna Chaitanya Chundru wrote:
>> If the bootloader has already powered up the PCIe PHY, doing a full
>> reset and waiting for it to come up again slows down boot time.
> 
> How big is the delay caused by it?
> 
>>
>> Add a check for PHY status and skip the reset steps when the PHY is
>> already active. In this case, only enable the required resources during
>> power-on. This works alongside the existing logic that skips the init
>> sequence.
> 
> Can we end up in a state where the bootloader has mis-setup the link? Or
> the link going bad because of any glitch during the bootup?

Good question, can we add a module parameter to force a full reset of the PHY in case
the bootloader is buggy ?

> 
>>
>> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
>> ---
>>   drivers/phy/qualcomm/phy-qcom-qmp-pcie.c | 28 ++++++++++++++++++----------
>>   1 file changed, 18 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
>> index 86b1b7e2da86a8675e3e48e90b782afb21cafd77..c93e613cf80b2612f0f225fa2125f78dbec1a33f 100644
>> --- a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
>> +++ b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
>> @@ -3153,6 +3153,7 @@ struct qmp_pcie {
>>   	const struct qmp_phy_cfg *cfg;
>>   	bool tcsr_4ln_config;
>>   	bool skip_init;
>> +	bool skip_reset;
>>   
>>   	void __iomem *serdes;
>>   	void __iomem *pcs;
>> @@ -4537,6 +4538,9 @@ static int qmp_pcie_init(struct phy *phy)
>>   		qphy_checkbits(pcs, cfg->regs[QPHY_START_CTRL], SERDES_START | PCS_START) &&
>>   		qphy_checkbits(pcs, cfg->regs[QPHY_PCS_POWER_DOWN_CONTROL], cfg->pwrdn_ctrl);
>>   
>> +	qmp->skip_reset = qmp->skip_init && !qphy_checkbits(pcs, cfg->regs[QPHY_PCS_STATUS],
> 
> It is definitely not a long-term state, there is no need to store it in
> qmp_pcie struct.
> 
>> +							    cfg->phy_status);
>> +
>>   	if (!qmp->skip_init && !cfg->tbls.serdes_num) {
>>   		dev_err(qmp->dev, "Init sequence not available\n");
>>   		return -ENODATA;
>> @@ -4560,13 +4564,15 @@ static int qmp_pcie_init(struct phy *phy)
>>   		}
>>   	}
>>   
>> -	ret = reset_control_assert(qmp->nocsr_reset);
>> -	if (ret) {
>> -		dev_err(qmp->dev, "no-csr reset assert failed\n");
>> -		goto err_assert_reset;
>> -	}
>> +	if (!qmp->skip_reset) {
>> +		ret = reset_control_assert(qmp->nocsr_reset);
>> +		if (ret) {
>> +			dev_err(qmp->dev, "no-csr reset assert failed\n");
>> +			goto err_assert_reset;
>> +		}
>>   
>> -	usleep_range(200, 300);
>> +		usleep_range(200, 300);
>> +	}
>>   
>>   	if (!qmp->skip_init) {
>>   		ret = reset_control_bulk_deassert(cfg->num_resets, qmp->resets);
>> @@ -4641,10 +4647,12 @@ static int qmp_pcie_power_on(struct phy *phy)
>>   	if (ret)
>>   		return ret;
>>   
>> -	ret = reset_control_deassert(qmp->nocsr_reset);
>> -	if (ret) {
>> -		dev_err(qmp->dev, "no-csr reset deassert failed\n");
>> -		goto err_disable_pipe_clk;
>> +	if (!qmp->skip_reset) {
>> +		ret = reset_control_deassert(qmp->nocsr_reset);
>> +		if (ret) {
>> +			dev_err(qmp->dev, "no-csr reset deassert failed\n");
>> +			goto err_disable_pipe_clk;
>> +		}
>>   	}
>>   
>>   	if (qmp->skip_init)
>>
>> -- 
>> 2.34.1
>>
>

Re: [PATCH 1/5] phy: qcom: qmp-pcie: Skip PHY reset if already up

Posted by Dmitry Baryshkov 1 month ago

On Fri, Jan 09, 2026 at 02:10:49PM +0100, Neil Armstrong wrote:
> On 1/9/26 14:08, Dmitry Baryshkov wrote:
> > On Fri, Jan 09, 2026 at 12:51:06PM +0530, Krishna Chaitanya Chundru wrote:
> > > If the bootloader has already powered up the PCIe PHY, doing a full
> > > reset and waiting for it to come up again slows down boot time.
> > 
> > How big is the delay caused by it?
> > 
> > > 
> > > Add a check for PHY status and skip the reset steps when the PHY is
> > > already active. In this case, only enable the required resources during
> > > power-on. This works alongside the existing logic that skips the init
> > > sequence.
> > 
> > Can we end up in a state where the bootloader has mis-setup the link? Or
> > the link going bad because of any glitch during the bootup?
> 
> Good question, can we add a module parameter to force a full reset of the PHY in case
> the bootloader is buggy ?

I'd suggest a simpler thing: if the reset was skipped, reset the PHY in
case of an error and retry. That's also one of the reasons why I asked
for skip_reset not to be the persistent value.

> 
> > 
> > > 
> > > Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
> > > ---
> > >   drivers/phy/qualcomm/phy-qcom-qmp-pcie.c | 28 ++++++++++++++++++----------
> > >   1 file changed, 18 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> > > index 86b1b7e2da86a8675e3e48e90b782afb21cafd77..c93e613cf80b2612f0f225fa2125f78dbec1a33f 100644
> > > --- a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> > > +++ b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> > > @@ -3153,6 +3153,7 @@ struct qmp_pcie {
> > >   	const struct qmp_phy_cfg *cfg;
> > >   	bool tcsr_4ln_config;
> > >   	bool skip_init;
> > > +	bool skip_reset;
> > >   	void __iomem *serdes;
> > >   	void __iomem *pcs;
> > > @@ -4537,6 +4538,9 @@ static int qmp_pcie_init(struct phy *phy)
> > >   		qphy_checkbits(pcs, cfg->regs[QPHY_START_CTRL], SERDES_START | PCS_START) &&
> > >   		qphy_checkbits(pcs, cfg->regs[QPHY_PCS_POWER_DOWN_CONTROL], cfg->pwrdn_ctrl);
> > > +	qmp->skip_reset = qmp->skip_init && !qphy_checkbits(pcs, cfg->regs[QPHY_PCS_STATUS],
> > 
> > It is definitely not a long-term state, there is no need to store it in
> > qmp_pcie struct.
> > 
> > > +							    cfg->phy_status);
> > > +
> > >   	if (!qmp->skip_init && !cfg->tbls.serdes_num) {
> > >   		dev_err(qmp->dev, "Init sequence not available\n");
> > >   		return -ENODATA;
> > > @@ -4560,13 +4564,15 @@ static int qmp_pcie_init(struct phy *phy)
> > >   		}
> > >   	}
> > > -	ret = reset_control_assert(qmp->nocsr_reset);
> > > -	if (ret) {
> > > -		dev_err(qmp->dev, "no-csr reset assert failed\n");
> > > -		goto err_assert_reset;
> > > -	}
> > > +	if (!qmp->skip_reset) {
> > > +		ret = reset_control_assert(qmp->nocsr_reset);
> > > +		if (ret) {
> > > +			dev_err(qmp->dev, "no-csr reset assert failed\n");
> > > +			goto err_assert_reset;
> > > +		}
> > > -	usleep_range(200, 300);
> > > +		usleep_range(200, 300);
> > > +	}
> > >   	if (!qmp->skip_init) {
> > >   		ret = reset_control_bulk_deassert(cfg->num_resets, qmp->resets);
> > > @@ -4641,10 +4647,12 @@ static int qmp_pcie_power_on(struct phy *phy)
> > >   	if (ret)
> > >   		return ret;
> > > -	ret = reset_control_deassert(qmp->nocsr_reset);
> > > -	if (ret) {
> > > -		dev_err(qmp->dev, "no-csr reset deassert failed\n");
> > > -		goto err_disable_pipe_clk;
> > > +	if (!qmp->skip_reset) {
> > > +		ret = reset_control_deassert(qmp->nocsr_reset);
> > > +		if (ret) {
> > > +			dev_err(qmp->dev, "no-csr reset deassert failed\n");
> > > +			goto err_disable_pipe_clk;
> > > +		}
> > >   	}
> > >   	if (qmp->skip_init)
> > > 
> > > -- 
> > > 2.34.1
> > > 
> > 
> 

-- 
With best wishes
Dmitry

Re: [PATCH 1/5] phy: qcom: qmp-pcie: Skip PHY reset if already up

Posted by Vinod Koul 3 weeks, 5 days ago

On 09-01-26, 16:03, Dmitry Baryshkov wrote:
> On Fri, Jan 09, 2026 at 02:10:49PM +0100, Neil Armstrong wrote:
> > On 1/9/26 14:08, Dmitry Baryshkov wrote:
> > > On Fri, Jan 09, 2026 at 12:51:06PM +0530, Krishna Chaitanya Chundru wrote:
> > > > If the bootloader has already powered up the PCIe PHY, doing a full
> > > > reset and waiting for it to come up again slows down boot time.
> > > 
> > > How big is the delay caused by it?
> > > 
> > > > 
> > > > Add a check for PHY status and skip the reset steps when the PHY is
> > > > already active. In this case, only enable the required resources during
> > > > power-on. This works alongside the existing logic that skips the init
> > > > sequence.
> > > 
> > > Can we end up in a state where the bootloader has mis-setup the link? Or
> > > the link going bad because of any glitch during the bootup?
> > 
> > Good question, can we add a module parameter to force a full reset of the PHY in case
> > the bootloader is buggy ?
> 
> I'd suggest a simpler thing: if the reset was skipped, reset the PHY in
> case of an error and retry. That's also one of the reasons why I asked
> for skip_reset not to be the persistent value.

That is a better suggestion. Helps skips if it is configured and way to
recover if buggy

-- 
~Vinod

Re: [PATCH 1/5] phy: qcom: qmp-pcie: Skip PHY reset if already up

Posted by Abel Vesa 1 month ago

On 26-01-09 12:51:06, Krishna Chaitanya Chundru wrote:
> If the bootloader has already powered up the PCIe PHY, doing a full
> reset and waiting for it to come up again slows down boot time.
> 
> Add a check for PHY status and skip the reset steps when the PHY is
> already active. In this case, only enable the required resources during
> power-on. This works alongside the existing logic that skips the init
> sequence.
> 
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>

Reviewed-by: Abel Vesa <abel.vesa@oss.qualcomm.com>