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SubjectRe: [PATCH v4] PCI/ASPM: Update LTR threshold based upon reported max latencies
Quoting Krishna chaitanya chundru (2022-06-03 00:54:19)
> 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.

Not sure why it's a reply to the previous rounds. I didn't notice this
patch for a bit. Can you stop sending as replies to the previous round?

> 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 | 32 ++++++++++++++++++++++++++++++++
> 1 file changed, 32 insertions(+)
>
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index a96b742..c8f6253 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);

Remove useless parenthesis please.

> +
> + max_nsnp_scale = (max_nosnoop_lat & PCI_LTR_SCALE_MASK) >> PCI_LTR_SCALE_SHIFT;
> + max_nsnp_val = (max_nosnoop_lat & PCI_LTR_VALUE_MASK)

Remove useless parenthesis please.

> +
> + /* choose the greater max scale value between snoop and no snoop value*/
> + max_scale = (max_snp_scale > max_nsnp_scale) ? max_snp_scale: max_nsnp_scale;

Use max()?

> +
> + /* choose the greater max value between snoop and no snoop scales */
> + max_val = (max_snp_val > max_nsnp_val) ? max_snp_val: max_nsnp_val;

Use max()?

> +
> /* 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 +523,16 @@ 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.
> + */
> + if (scale > max_scale)
> + scale = max_scale;

Use min()?

> + if (value > max_val)
> + value = max_val;

Use min()?

> +
> ctl1 |= t_common_mode << 8 | scale << 29 | value << 16;
>
> /* Some broken devices only support dword access to L1 SS */

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