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[v5] PCI/ASPM: Update LTR threshold based upon reported max latencies

Message ID 1654837710-30561-1-git-send-email-quic_krichai@quicinc.com
State New
Headers show
Series [v5] PCI/ASPM: Update LTR threshold based upon reported max latencies | expand

Commit Message

Krishna chaitanya chundru June 10, 2022, 5:08 a.m. UTC 
From: Prasad Malisetty <quic_pmaliset@quicinc.com>

In ASPM driver, LTR threshold scale and value are updated based on
tcommon_mode and t_poweron values. In kioxia NVMe L1.2 is failing due to
LTR threshold scale and value are greater values than max snoop/non-snoop
value.

Based on PCIe r4.1, sec 5.5.1, L1.2 substate must be entered when
reported snoop/no-snoop values is greather than or equal to
LTR_L1.2_THRESHOLD value.

Signed-off-by: Prasad Malisetty  <quic_pmaliset@quicinc.com>
Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
---

I am taking this patch forward as prasad is no more working with our org.
Changes since v4:
	- Replaced conditional statements with min and max.
changes since v3:
	- Changed the logic to include this condition "snoop/nosnoop
	  latencies are not equal to zero and lower than LTR_L1.2_THRESHOLD"
Changes since v2:
	- Replaced LTRME logic with max snoop/no-snoop latencies check.
Changes since v1:
	- Added missing variable declaration in v1 patch
---
 drivers/pci/pcie/aspm.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

Comments

Krishna chaitanya chundru June 15, 2022, 1:23 p.m. UTC | #1 
A Gentle remainder please review it.

On 6/10/2022 10:38 AM, Krishna chaitanya chundru wrote:
> From: Prasad Malisetty <quic_pmaliset@quicinc.com>
>
> In ASPM driver, LTR threshold scale and value are updated based on
> tcommon_mode and t_poweron values. In kioxia NVMe L1.2 is failing due to
> LTR threshold scale and value are greater values than max snoop/non-snoop
> value.
>
> Based on PCIe r4.1, sec 5.5.1, L1.2 substate must be entered when
> reported snoop/no-snoop values is greather than or equal to
> LTR_L1.2_THRESHOLD value.
>
> Signed-off-by: Prasad Malisetty  <quic_pmaliset@quicinc.com>
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
> ---
>
> I am taking this patch forward as prasad is no more working with our org.
> Changes since v4:
> 	- Replaced conditional statements with min and max.
> changes since v3:
> 	- Changed the logic to include this condition "snoop/nosnoop
> 	  latencies are not equal to zero and lower than LTR_L1.2_THRESHOLD"
> Changes since v2:
> 	- Replaced LTRME logic with max snoop/no-snoop latencies check.
> Changes since v1:
> 	- Added missing variable declaration in v1 patch
> ---
>   drivers/pci/pcie/aspm.c | 30 ++++++++++++++++++++++++++++++
>   1 file changed, 30 insertions(+)
>
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index a96b742..676c03e 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -461,14 +461,36 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
>   {
>   	struct pci_dev *child = link->downstream, *parent = link->pdev;
>   	u32 val1, val2, scale1, scale2;
> +	u32 max_val, max_scale, max_snp_scale, max_snp_val, max_nsnp_scale, max_nsnp_val;
>   	u32 t_common_mode, t_power_on, l1_2_threshold, scale, value;
>   	u32 ctl1 = 0, ctl2 = 0;
>   	u32 pctl1, pctl2, cctl1, cctl2;
>   	u32 pl1_2_enables, cl1_2_enables;
> +	u16 ltr;
> +	u16 max_snoop_lat, max_nosnoop_lat;
>   
>   	if (!(link->aspm_support & ASPM_STATE_L1_2_MASK))
>   		return;
>   
> +	ltr = pci_find_ext_capability(child, PCI_EXT_CAP_ID_LTR);
> +	if (!ltr)
> +		return;
> +
> +	pci_read_config_word(child, ltr + PCI_LTR_MAX_SNOOP_LAT, &max_snoop_lat);
> +	pci_read_config_word(child, ltr + PCI_LTR_MAX_NOSNOOP_LAT, &max_nosnoop_lat);
> +
> +	max_snp_scale = (max_snoop_lat & PCI_LTR_SCALE_MASK) >> PCI_LTR_SCALE_SHIFT;
> +	max_snp_val = max_snoop_lat & PCI_LTR_VALUE_MASK;
> +
> +	max_nsnp_scale = (max_nosnoop_lat & PCI_LTR_SCALE_MASK) >> PCI_LTR_SCALE_SHIFT;
> +	max_nsnp_val = max_nosnoop_lat & PCI_LTR_VALUE_MASK;
> +
> +	/* choose the greater max scale value between snoop and no snoop value*/
> +	max_scale = max(max_snp_scale, max_nsnp_scale);
> +
> +	/* choose the greater max value between snoop and no snoop scales */
> +	max_val = max(max_snp_val, max_nsnp_val);
> +
>   	/* Choose the greater of the two Port Common_Mode_Restore_Times */
>   	val1 = (parent_l1ss_cap & PCI_L1SS_CAP_CM_RESTORE_TIME) >> 8;
>   	val2 = (child_l1ss_cap & PCI_L1SS_CAP_CM_RESTORE_TIME) >> 8;
> @@ -501,6 +523,14 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
>   	 */
>   	l1_2_threshold = 2 + 4 + t_common_mode + t_power_on;
>   	encode_l12_threshold(l1_2_threshold, &scale, &value);
> +
> +	/*
> +	 * Based on PCIe r4.1, sec 5.5.1, L1.2 substate must be entered when reported
> +	 * snoop/no-snoop values are greather than or equal to LTR_L1.2_THRESHOLD value.
> +	 */
> +	scale = min(scale, max_scale);
> +	value = min(value, max_val);
> +
>   	ctl1 |= t_common_mode << 8 | scale << 29 | value << 16;
>   
>   	/* Some broken devices only support dword access to L1 SS */
Manivannan Sadhasivam June 15, 2022, 5:39 p.m. UTC | #2 
On Fri, Jun 10, 2022 at 10:38:28AM +0530, Krishna chaitanya chundru wrote:
> From: Prasad Malisetty <quic_pmaliset@quicinc.com>
> 
> In ASPM driver, LTR threshold scale and value are updated based on
> tcommon_mode and t_poweron values. In kioxia NVMe L1.2 is failing due to
> LTR threshold scale and value are greater values than max snoop/non-snoop
> value.
> 
> Based on PCIe r4.1, sec 5.5.1, L1.2 substate must be entered when
> reported snoop/no-snoop values is greather than or equal to
> LTR_L1.2_THRESHOLD value.
> 
> Signed-off-by: Prasad Malisetty  <quic_pmaliset@quicinc.com>
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>

Acked-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Thanks,
Mani

> ---
> 
> I am taking this patch forward as prasad is no more working with our org.
> Changes since v4:
> 	- Replaced conditional statements with min and max.
> changes since v3:
> 	- Changed the logic to include this condition "snoop/nosnoop
> 	  latencies are not equal to zero and lower than LTR_L1.2_THRESHOLD"
> Changes since v2:
> 	- Replaced LTRME logic with max snoop/no-snoop latencies check.
> Changes since v1:
> 	- Added missing variable declaration in v1 patch
> ---
>  drivers/pci/pcie/aspm.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index a96b742..676c03e 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -461,14 +461,36 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
>  {
>  	struct pci_dev *child = link->downstream, *parent = link->pdev;
>  	u32 val1, val2, scale1, scale2;
> +	u32 max_val, max_scale, max_snp_scale, max_snp_val, max_nsnp_scale, max_nsnp_val;
>  	u32 t_common_mode, t_power_on, l1_2_threshold, scale, value;
>  	u32 ctl1 = 0, ctl2 = 0;
>  	u32 pctl1, pctl2, cctl1, cctl2;
>  	u32 pl1_2_enables, cl1_2_enables;
> +	u16 ltr;
> +	u16 max_snoop_lat, max_nosnoop_lat;
>  
>  	if (!(link->aspm_support & ASPM_STATE_L1_2_MASK))
>  		return;
>  
> +	ltr = pci_find_ext_capability(child, PCI_EXT_CAP_ID_LTR);
> +	if (!ltr)
> +		return;
> +
> +	pci_read_config_word(child, ltr + PCI_LTR_MAX_SNOOP_LAT, &max_snoop_lat);
> +	pci_read_config_word(child, ltr + PCI_LTR_MAX_NOSNOOP_LAT, &max_nosnoop_lat);
> +
> +	max_snp_scale = (max_snoop_lat & PCI_LTR_SCALE_MASK) >> PCI_LTR_SCALE_SHIFT;
> +	max_snp_val = max_snoop_lat & PCI_LTR_VALUE_MASK;
> +
> +	max_nsnp_scale = (max_nosnoop_lat & PCI_LTR_SCALE_MASK) >> PCI_LTR_SCALE_SHIFT;
> +	max_nsnp_val = max_nosnoop_lat & PCI_LTR_VALUE_MASK;
> +
> +	/* choose the greater max scale value between snoop and no snoop value*/
> +	max_scale = max(max_snp_scale, max_nsnp_scale);
> +
> +	/* choose the greater max value between snoop and no snoop scales */
> +	max_val = max(max_snp_val, max_nsnp_val);
> +
>  	/* Choose the greater of the two Port Common_Mode_Restore_Times */
>  	val1 = (parent_l1ss_cap & PCI_L1SS_CAP_CM_RESTORE_TIME) >> 8;
>  	val2 = (child_l1ss_cap & PCI_L1SS_CAP_CM_RESTORE_TIME) >> 8;
> @@ -501,6 +523,14 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
>  	 */
>  	l1_2_threshold = 2 + 4 + t_common_mode + t_power_on;
>  	encode_l12_threshold(l1_2_threshold, &scale, &value);
> +
> +	/*
> +	 * Based on PCIe r4.1, sec 5.5.1, L1.2 substate must be entered when reported
> +	 * snoop/no-snoop values are greather than or equal to LTR_L1.2_THRESHOLD value.
> +	 */
> +	scale = min(scale, max_scale);
> +	value = min(value, max_val);
> +
>  	ctl1 |= t_common_mode << 8 | scale << 29 | value << 16;
>  
>  	/* Some broken devices only support dword access to L1 SS */
> -- 
> 2.7.4
>
Manivannan Sadhasivam July 15, 2022, 8:28 a.m. UTC | #3 
On Wed, Jun 15, 2022 at 06:53:18PM +0530, Krishna Chaitanya Chundru wrote:
> A Gentle remainder please review it.
> 
> On 6/10/2022 10:38 AM, Krishna chaitanya chundru wrote:
> > From: Prasad Malisetty <quic_pmaliset@quicinc.com>
> > 
> > In ASPM driver, LTR threshold scale and value are updated based on
> > tcommon_mode and t_poweron values. In kioxia NVMe L1.2 is failing due to
> > LTR threshold scale and value are greater values than max snoop/non-snoop
> > value.
> > 
> > Based on PCIe r4.1, sec 5.5.1, L1.2 substate must be entered when
> > reported snoop/no-snoop values is greather than or equal to
> > LTR_L1.2_THRESHOLD value.
> > 
> > Signed-off-by: Prasad Malisetty  <quic_pmaliset@quicinc.com>
> > Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>

As Stephen noted in previous verison, you should sent the newer versions
separately and not as a reply to previous ones. So please sent v6 with
my tag as well.

Thanks,
Mani

> > ---
> > 
> > I am taking this patch forward as prasad is no more working with our org.
> > Changes since v4:
> > 	- Replaced conditional statements with min and max.
> > changes since v3:
> > 	- Changed the logic to include this condition "snoop/nosnoop
> > 	  latencies are not equal to zero and lower than LTR_L1.2_THRESHOLD"
> > Changes since v2:
> > 	- Replaced LTRME logic with max snoop/no-snoop latencies check.
> > Changes since v1:
> > 	- Added missing variable declaration in v1 patch
> > ---
> >   drivers/pci/pcie/aspm.c | 30 ++++++++++++++++++++++++++++++
> >   1 file changed, 30 insertions(+)
> > 
> > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> > index a96b742..676c03e 100644
> > --- a/drivers/pci/pcie/aspm.c
> > +++ b/drivers/pci/pcie/aspm.c
> > @@ -461,14 +461,36 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
> >   {
> >   	struct pci_dev *child = link->downstream, *parent = link->pdev;
> >   	u32 val1, val2, scale1, scale2;
> > +	u32 max_val, max_scale, max_snp_scale, max_snp_val, max_nsnp_scale, max_nsnp_val;
> >   	u32 t_common_mode, t_power_on, l1_2_threshold, scale, value;
> >   	u32 ctl1 = 0, ctl2 = 0;
> >   	u32 pctl1, pctl2, cctl1, cctl2;
> >   	u32 pl1_2_enables, cl1_2_enables;
> > +	u16 ltr;
> > +	u16 max_snoop_lat, max_nosnoop_lat;
> >   	if (!(link->aspm_support & ASPM_STATE_L1_2_MASK))
> >   		return;
> > +	ltr = pci_find_ext_capability(child, PCI_EXT_CAP_ID_LTR);
> > +	if (!ltr)
> > +		return;
> > +
> > +	pci_read_config_word(child, ltr + PCI_LTR_MAX_SNOOP_LAT, &max_snoop_lat);
> > +	pci_read_config_word(child, ltr + PCI_LTR_MAX_NOSNOOP_LAT, &max_nosnoop_lat);
> > +
> > +	max_snp_scale = (max_snoop_lat & PCI_LTR_SCALE_MASK) >> PCI_LTR_SCALE_SHIFT;
> > +	max_snp_val = max_snoop_lat & PCI_LTR_VALUE_MASK;
> > +
> > +	max_nsnp_scale = (max_nosnoop_lat & PCI_LTR_SCALE_MASK) >> PCI_LTR_SCALE_SHIFT;
> > +	max_nsnp_val = max_nosnoop_lat & PCI_LTR_VALUE_MASK;
> > +
> > +	/* choose the greater max scale value between snoop and no snoop value*/
> > +	max_scale = max(max_snp_scale, max_nsnp_scale);
> > +
> > +	/* choose the greater max value between snoop and no snoop scales */
> > +	max_val = max(max_snp_val, max_nsnp_val);
> > +
> >   	/* Choose the greater of the two Port Common_Mode_Restore_Times */
> >   	val1 = (parent_l1ss_cap & PCI_L1SS_CAP_CM_RESTORE_TIME) >> 8;
> >   	val2 = (child_l1ss_cap & PCI_L1SS_CAP_CM_RESTORE_TIME) >> 8;
> > @@ -501,6 +523,14 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
> >   	 */
> >   	l1_2_threshold = 2 + 4 + t_common_mode + t_power_on;
> >   	encode_l12_threshold(l1_2_threshold, &scale, &value);
> > +
> > +	/*
> > +	 * Based on PCIe r4.1, sec 5.5.1, L1.2 substate must be entered when reported
> > +	 * snoop/no-snoop values are greather than or equal to LTR_L1.2_THRESHOLD value.
> > +	 */
> > +	scale = min(scale, max_scale);
> > +	value = min(value, max_val);
> > +
> >   	ctl1 |= t_common_mode << 8 | scale << 29 | value << 16;
> >   	/* Some broken devices only support dword access to L1 SS */
Krishna chaitanya chundru July 15, 2022, 11:28 a.m. UTC | #4 
On 7/15/2022 1:58 PM, Manivannan Sadhasivam wrote:
> On Wed, Jun 15, 2022 at 06:53:18PM +0530, Krishna Chaitanya Chundru wrote:
>> A Gentle remainder please review it.
>>
>> On 6/10/2022 10:38 AM, Krishna chaitanya chundru wrote:
>>> From: Prasad Malisetty <quic_pmaliset@quicinc.com>
>>>
>>> In ASPM driver, LTR threshold scale and value are updated based on
>>> tcommon_mode and t_poweron values. In kioxia NVMe L1.2 is failing due to
>>> LTR threshold scale and value are greater values than max snoop/non-snoop
>>> value.
>>>
>>> Based on PCIe r4.1, sec 5.5.1, L1.2 substate must be entered when
>>> reported snoop/no-snoop values is greather than or equal to
>>> LTR_L1.2_THRESHOLD value.
>>>
>>> Signed-off-by: Prasad Malisetty  <quic_pmaliset@quicinc.com>
>>> Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
> As Stephen noted in previous verison, you should sent the newer versions
> separately and not as a reply to previous ones. So please sent v6 with
> my tag as well.
>
> Thanks,
> Mani

ok mani I will send the v6 as you suggested.


Thanks

Krishna chaitanya.

>
>>> ---
>>>
>>> I am taking this patch forward as prasad is no more working with our org.
>>> Changes since v4:
>>> 	- Replaced conditional statements with min and max.
>>> changes since v3:
>>> 	- Changed the logic to include this condition "snoop/nosnoop
>>> 	  latencies are not equal to zero and lower than LTR_L1.2_THRESHOLD"
>>> Changes since v2:
>>> 	- Replaced LTRME logic with max snoop/no-snoop latencies check.
>>> Changes since v1:
>>> 	- Added missing variable declaration in v1 patch
>>> ---
>>>    drivers/pci/pcie/aspm.c | 30 ++++++++++++++++++++++++++++++
>>>    1 file changed, 30 insertions(+)
>>>
>>> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
>>> index a96b742..676c03e 100644
>>> --- a/drivers/pci/pcie/aspm.c
>>> +++ b/drivers/pci/pcie/aspm.c
>>> @@ -461,14 +461,36 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
>>>    {
>>>    	struct pci_dev *child = link->downstream, *parent = link->pdev;
>>>    	u32 val1, val2, scale1, scale2;
>>> +	u32 max_val, max_scale, max_snp_scale, max_snp_val, max_nsnp_scale, max_nsnp_val;
>>>    	u32 t_common_mode, t_power_on, l1_2_threshold, scale, value;
>>>    	u32 ctl1 = 0, ctl2 = 0;
>>>    	u32 pctl1, pctl2, cctl1, cctl2;
>>>    	u32 pl1_2_enables, cl1_2_enables;
>>> +	u16 ltr;
>>> +	u16 max_snoop_lat, max_nosnoop_lat;
>>>    	if (!(link->aspm_support & ASPM_STATE_L1_2_MASK))
>>>    		return;
>>> +	ltr = pci_find_ext_capability(child, PCI_EXT_CAP_ID_LTR);
>>> +	if (!ltr)
>>> +		return;
>>> +
>>> +	pci_read_config_word(child, ltr + PCI_LTR_MAX_SNOOP_LAT, &max_snoop_lat);
>>> +	pci_read_config_word(child, ltr + PCI_LTR_MAX_NOSNOOP_LAT, &max_nosnoop_lat);
>>> +
>>> +	max_snp_scale = (max_snoop_lat & PCI_LTR_SCALE_MASK) >> PCI_LTR_SCALE_SHIFT;
>>> +	max_snp_val = max_snoop_lat & PCI_LTR_VALUE_MASK;
>>> +
>>> +	max_nsnp_scale = (max_nosnoop_lat & PCI_LTR_SCALE_MASK) >> PCI_LTR_SCALE_SHIFT;
>>> +	max_nsnp_val = max_nosnoop_lat & PCI_LTR_VALUE_MASK;
>>> +
>>> +	/* choose the greater max scale value between snoop and no snoop value*/
>>> +	max_scale = max(max_snp_scale, max_nsnp_scale);
>>> +
>>> +	/* choose the greater max value between snoop and no snoop scales */
>>> +	max_val = max(max_snp_val, max_nsnp_val);
>>> +
>>>    	/* Choose the greater of the two Port Common_Mode_Restore_Times */
>>>    	val1 = (parent_l1ss_cap & PCI_L1SS_CAP_CM_RESTORE_TIME) >> 8;
>>>    	val2 = (child_l1ss_cap & PCI_L1SS_CAP_CM_RESTORE_TIME) >> 8;
>>> @@ -501,6 +523,14 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
>>>    	 */
>>>    	l1_2_threshold = 2 + 4 + t_common_mode + t_power_on;
>>>    	encode_l12_threshold(l1_2_threshold, &scale, &value);
>>> +
>>> +	/*
>>> +	 * Based on PCIe r4.1, sec 5.5.1, L1.2 substate must be entered when reported
>>> +	 * snoop/no-snoop values are greather than or equal to LTR_L1.2_THRESHOLD value.
>>> +	 */
>>> +	scale = min(scale, max_scale);
>>> +	value = min(value, max_val);
>>> +
>>>    	ctl1 |= t_common_mode << 8 | scale << 29 | value << 16;
>>>    	/* Some broken devices only support dword access to L1 SS */
diff mbox series

Patch

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index a96b742..676c03e 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -461,14 +461,36 @@  static void aspm_calc_l1ss_info(struct pcie_link_state *link,
 {
 	struct pci_dev *child = link->downstream, *parent = link->pdev;
 	u32 val1, val2, scale1, scale2;
+	u32 max_val, max_scale, max_snp_scale, max_snp_val, max_nsnp_scale, max_nsnp_val;
 	u32 t_common_mode, t_power_on, l1_2_threshold, scale, value;
 	u32 ctl1 = 0, ctl2 = 0;
 	u32 pctl1, pctl2, cctl1, cctl2;
 	u32 pl1_2_enables, cl1_2_enables;
+	u16 ltr;
+	u16 max_snoop_lat, max_nosnoop_lat;
 
 	if (!(link->aspm_support & ASPM_STATE_L1_2_MASK))
 		return;
 
+	ltr = pci_find_ext_capability(child, PCI_EXT_CAP_ID_LTR);
+	if (!ltr)
+		return;
+
+	pci_read_config_word(child, ltr + PCI_LTR_MAX_SNOOP_LAT, &max_snoop_lat);
+	pci_read_config_word(child, ltr + PCI_LTR_MAX_NOSNOOP_LAT, &max_nosnoop_lat);
+
+	max_snp_scale = (max_snoop_lat & PCI_LTR_SCALE_MASK) >> PCI_LTR_SCALE_SHIFT;
+	max_snp_val = max_snoop_lat & PCI_LTR_VALUE_MASK;
+
+	max_nsnp_scale = (max_nosnoop_lat & PCI_LTR_SCALE_MASK) >> PCI_LTR_SCALE_SHIFT;
+	max_nsnp_val = max_nosnoop_lat & PCI_LTR_VALUE_MASK;
+
+	/* choose the greater max scale value between snoop and no snoop value*/
+	max_scale = max(max_snp_scale, max_nsnp_scale);
+
+	/* choose the greater max value between snoop and no snoop scales */
+	max_val = max(max_snp_val, max_nsnp_val);
+
 	/* Choose the greater of the two Port Common_Mode_Restore_Times */
 	val1 = (parent_l1ss_cap & PCI_L1SS_CAP_CM_RESTORE_TIME) >> 8;
 	val2 = (child_l1ss_cap & PCI_L1SS_CAP_CM_RESTORE_TIME) >> 8;
@@ -501,6 +523,14 @@  static void aspm_calc_l1ss_info(struct pcie_link_state *link,
 	 */
 	l1_2_threshold = 2 + 4 + t_common_mode + t_power_on;
 	encode_l12_threshold(l1_2_threshold, &scale, &value);
+
+	/*
+	 * Based on PCIe r4.1, sec 5.5.1, L1.2 substate must be entered when reported
+	 * snoop/no-snoop values are greather than or equal to LTR_L1.2_THRESHOLD value.
+	 */
+	scale = min(scale, max_scale);
+	value = min(value, max_val);
+
 	ctl1 |= t_common_mode << 8 | scale << 29 | value << 16;
 
 	/* Some broken devices only support dword access to L1 SS */