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

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