diff mbox series

[v3] PCI/ASPM: Update LTR threshold based upon reported max latencies

Message ID 1654086232-17055-1-git-send-email-quic_krichai@quicinc.com (mailing list archive)
State Superseded
Headers show
Series [v3] PCI/ASPM: Update LTR threshold based upon reported max latencies | expand

Commit Message

Krishna Chaitanya Chundru June 1, 2022, 12:23 p.m. UTC 
In ASPM driver, LTR threshold scale and value is updating based on
tcommon_mode and t_poweron values. In kioxia NVMe L1.2 is failing due to
LTR threshold scale and value is 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.

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

I am takking this patch forward as prasad is no more working with our org.

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 | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

Comments

Krishna Chaitanya Chundru June 1, 2022, 12:27 p.m. UTC | #1 
[+cc kenny, vidya]

On 6/1/2022 5:53 PM, Krishna chaitanya chundru wrote:
> In ASPM driver, LTR threshold scale and value is updating based on
> tcommon_mode and t_poweron values. In kioxia NVMe L1.2 is failing due to
> LTR threshold scale and value is 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.
>
> Suggested-by: Prasad Malisetty  <quic_pmaliset@quicinc.com>
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
> ---
>
> I am takking this patch forward as prasad is no more working with our org.
>
> 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 | 22 +++++++++++++++++++++-
>   1 file changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index a96b742..4a15e50 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -465,10 +465,19 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
>   	u32 ctl1 = 0, ctl2 = 0;
>   	u32 pctl1, pctl2, cctl1, cctl2;
>   	u32 pl1_2_enables, cl1_2_enables;
> +	int ltr;
> +	u16 max_snoop_lat = 0, max_nosnoop_lat = 0;
>   
>   	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);
> +
>   	/* 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;
> @@ -501,7 +510,18 @@ 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);
> -	ctl1 |= t_common_mode << 8 | scale << 29 | value << 16;
> +
> +	/*
> +	 * If the max snoop and no snoop latencies are '0', then avoid updating scale
> +	 * and 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.
> +	 */
> +	if ((max_snoop_lat == 0) && (max_nosnoop_lat == 0))
> +		ctl1 |= t_common_mode << 8;
> +	else
> +		ctl1 |= t_common_mode << 8 | scale << 29 | value << 16;
>   
>   	/* Some broken devices only support dword access to L1 SS */
>   	pci_read_config_dword(parent, parent->l1ss + PCI_L1SS_CTL1, &pctl1);
Manivannan Sadhasivam June 2, 2022, 8:29 a.m. UTC | #2 
On Wed, Jun 01, 2022 at 05:57:53PM +0530, Krishna Chaitanya Chundru wrote:
> [+cc kenny, vidya]
> 
> On 6/1/2022 5:53 PM, Krishna chaitanya chundru wrote:
> > In ASPM driver, LTR threshold scale and value is updating based on

s/is/are

s/updating/updated

> > tcommon_mode and t_poweron values. In kioxia NVMe L1.2 is failing due to
> > LTR threshold scale and value is greater values than max snoop/non-snoop

s/is/are

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

If you are inheriting the patch from Prasad, then you should still give the
authorship to him (unless the patch has changed significantly). You can add
your S-o-b tag to convey that you are carrying the patch from him.

> > ---
> > 
> > I am takking this patch forward as prasad is no more working with our org.
> > 
> > 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 | 22 +++++++++++++++++++++-
> >   1 file changed, 21 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> > index a96b742..4a15e50 100644
> > --- a/drivers/pci/pcie/aspm.c
> > +++ b/drivers/pci/pcie/aspm.c
> > @@ -465,10 +465,19 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
> >   	u32 ctl1 = 0, ctl2 = 0;
> >   	u32 pctl1, pctl2, cctl1, cctl2;
> >   	u32 pl1_2_enables, cl1_2_enables;
> > +	int ltr;

This could be u16 too.

> > +	u16 max_snoop_lat = 0, max_nosnoop_lat = 0;

No need to initialize these variables.

> >   	if (!(link->aspm_support & ASPM_STATE_L1_2_MASK))
> >   		return;
> > +	ltr = pci_find_ext_capability(child, PCI_EXT_CAP_ID_LTR);
> > +	if (!ltr)
> > +		return;

Is this capability implemented always?

> > +
> > +	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);
> > +
> >   	/* 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;
> > @@ -501,7 +510,18 @@ 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);
> > -	ctl1 |= t_common_mode << 8 | scale << 29 | value << 16;
> > +
> > +	/*
> > +	 * If the max snoop and no snoop latencies are '0', then avoid updating scale
> > +	 * and value.
> > +	 *

This looks fine but...

> > +	 * 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.

s/is/are

What about this? What if the snoop/nosnoop latencies are not equal to zero and
lower than LTR_L1.2_THRESHOLD?

Thanks,
Mani

> > +	 */
> > +	if ((max_snoop_lat == 0) && (max_nosnoop_lat == 0))
> > +		ctl1 |= t_common_mode << 8;
> > +	else
> > +		ctl1 |= t_common_mode << 8 | scale << 29 | value << 16;
> >   	/* Some broken devices only support dword access to L1 SS */
> >   	pci_read_config_dword(parent, parent->l1ss + PCI_L1SS_CTL1, &pctl1);
Krishna Chaitanya Chundru June 2, 2022, 9:59 a.m. UTC | #3 
On 6/2/2022 1:59 PM, Manivannan Sadhasivam wrote:
> On Wed, Jun 01, 2022 at 05:57:53PM +0530, Krishna Chaitanya Chundru wrote:
>> [+cc kenny, vidya]
>>
>> On 6/1/2022 5:53 PM, Krishna chaitanya chundru wrote:
>>> In ASPM driver, LTR threshold scale and value is updating based on
> s/is/are
>
> s/updating/updated
>
>>> tcommon_mode and t_poweron values. In kioxia NVMe L1.2 is failing due to
>>> LTR threshold scale and value is greater values than max snoop/non-snoop
> s/is/are
>
>>> 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.
>>>
>>> Suggested-by: Prasad Malisetty  <quic_pmaliset@quicinc.com>
>>> Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
> If you are inheriting the patch from Prasad, then you should still give the
> authorship to him (unless the patch has changed significantly). You can add
> your S-o-b tag to convey that you are carrying the patch from him.
Thanks mani for pointing this, I will modify this in next patch.
>>> ---
>>>
>>> I am takking this patch forward as prasad is no more working with our org.
>>>
>>> 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 | 22 +++++++++++++++++++++-
>>>    1 file changed, 21 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
>>> index a96b742..4a15e50 100644
>>> --- a/drivers/pci/pcie/aspm.c
>>> +++ b/drivers/pci/pcie/aspm.c
>>> @@ -465,10 +465,19 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
>>>    	u32 ctl1 = 0, ctl2 = 0;
>>>    	u32 pctl1, pctl2, cctl1, cctl2;
>>>    	u32 pl1_2_enables, cl1_2_enables;
>>> +	int ltr;
> This could be u16 too.
Will change in the next patch
>>> +	u16 max_snoop_lat = 0, max_nosnoop_lat = 0;
> No need to initialize these variables.
I will update these in next patch.
>>>    	if (!(link->aspm_support & ASPM_STATE_L1_2_MASK))
>>>    		return;
>>> +	ltr = pci_find_ext_capability(child, PCI_EXT_CAP_ID_LTR);
>>> +	if (!ltr)
>>> +		return;
> Is this capability implemented always?

Based up on spec 4.1, sec 5.5 Ports that support the L1.2 substate for 
ASPM L1 must support this.

And there is already a check in this function  if there is no L1.2 
support the function is returning.

>>> +
>>> +	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);
>>> +
>>>    	/* 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;
>>> @@ -501,7 +510,18 @@ 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);
>>> -	ctl1 |= t_common_mode << 8 | scale << 29 | value << 16;
>>> +
>>> +	/*
>>> +	 * If the max snoop and no snoop latencies are '0', then avoid updating scale
>>> +	 * and value.
>>> +	 *
> This looks fine but...
>
>>> +	 * 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.
> s/is/are
>
> What about this? What if the snoop/nosnoop latencies are not equal to zero and
> lower than LTR_L1.2_THRESHOLD?
>
> Thanks,
> Mani

Will address this in next patch.

Thanks,

Krishna Chaitanya.

>>> +	 */
>>> +	if ((max_snoop_lat == 0) && (max_nosnoop_lat == 0))
>>> +		ctl1 |= t_common_mode << 8;
>>> +	else
>>> +		ctl1 |= t_common_mode << 8 | scale << 29 | value << 16;
>>>    	/* Some broken devices only support dword access to L1 SS */
>>>    	pci_read_config_dword(parent, parent->l1ss + PCI_L1SS_CTL1, &pctl1);
diff mbox series

Patch

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index a96b742..4a15e50 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -465,10 +465,19 @@  static void aspm_calc_l1ss_info(struct pcie_link_state *link,
 	u32 ctl1 = 0, ctl2 = 0;
 	u32 pctl1, pctl2, cctl1, cctl2;
 	u32 pl1_2_enables, cl1_2_enables;
+	int ltr;
+	u16 max_snoop_lat = 0, max_nosnoop_lat = 0;
 
 	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);
+
 	/* 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;
@@ -501,7 +510,18 @@  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);
-	ctl1 |= t_common_mode << 8 | scale << 29 | value << 16;
+
+	/*
+	 * If the max snoop and no snoop latencies are '0', then avoid updating scale
+	 * and 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.
+	 */
+	if ((max_snoop_lat == 0) && (max_nosnoop_lat == 0))
+		ctl1 |= t_common_mode << 8;
+	else
+		ctl1 |= t_common_mode << 8 | scale << 29 | value << 16;
 
 	/* Some broken devices only support dword access to L1 SS */
 	pci_read_config_dword(parent, parent->l1ss + PCI_L1SS_CTL1, &pctl1);