lspci: Decode only supported ASPM exit latencies

Per the PCIe spec (r3.0, sec 7.8.6), the L0s Exit Latency is only valid
when L0s is supported, and similarly the L1 Exit Latency is only valid when
L1 is supported.

Only decode the L0s and L1 Exit Latencies if they are defined.

Correct the comments on the PCI_EXP_LNKCAP_L0S and PCI_EXP_LNKCAP_L1
definitions.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
 lib/header.h |    4 ++--
 ls-caps.c    |   14 ++++++++++----
 2 files changed, 12 insertions(+), 6 deletions(-)


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Hi Martin,

On Wed, Apr 29, 2015 at 10:25 AM, Bjorn Helgaas <bhelgaas@google.com> wrote:
> Per the PCIe spec (r3.0, sec 7.8.6), the L0s Exit Latency is only valid
> when L0s is supported, and similarly the L1 Exit Latency is only valid when
> L1 is supported.
>
> Only decode the L0s and L1 Exit Latencies if they are defined.
>
> Correct the comments on the PCI_EXP_LNKCAP_L0S and PCI_EXP_LNKCAP_L1
> definitions.
>
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> ---
>  lib/header.h |    4 ++--
>  ls-caps.c    |   14 ++++++++++----
>  2 files changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/lib/header.h b/lib/header.h
> index 8ee7565..47c7bc2 100644
> --- a/lib/header.h
> +++ b/lib/header.h
> @@ -772,8 +772,8 @@
>  #define  PCI_EXP_LNKCAP_SPEED  0x0000f /* Maximum Link Speed */
>  #define  PCI_EXP_LNKCAP_WIDTH  0x003f0 /* Maximum Link Width */
>  #define  PCI_EXP_LNKCAP_ASPM   0x00c00 /* Active State Power Management */
> -#define  PCI_EXP_LNKCAP_L0S    0x07000 /* L0s Acceptable Latency */
> -#define  PCI_EXP_LNKCAP_L1     0x38000 /* L1 Acceptable Latency */
> +#define  PCI_EXP_LNKCAP_L0S    0x07000 /* L0s Exit Latency */
> +#define  PCI_EXP_LNKCAP_L1     0x38000 /* L1 Exit Latency */
>  #define  PCI_EXP_LNKCAP_CLOCKPM        0x40000 /* Clock Power Management */
>  #define  PCI_EXP_LNKCAP_SURPRISE 0x80000 /* Surprise Down Error Reporting */
>  #define  PCI_EXP_LNKCAP_DLLA   0x100000 /* Data Link Layer Active Reporting */
> diff --git a/ls-caps.c b/ls-caps.c
> index c145ed6..24d6a29 100644
> --- a/ls-caps.c
> +++ b/ls-caps.c
> @@ -755,16 +755,22 @@ static const char *aspm_enabled(int code)
>
>  static void cap_express_link(struct device *d, int where, int type)
>  {
> -  u32 t;
> +  u32 t, aspm;
>    u16 w;
>
>    t = get_conf_long(d, where + PCI_EXP_LNKCAP);
> -  printf("\t\tLnkCap:\tPort #%d, Speed %s, Width x%d, ASPM %s, Exit Latency L0s %s, L1 %s\n",
> +  aspm = (t & PCI_EXP_LNKCAP_ASPM) >> 10;
> +  printf("\t\tLnkCap:\tPort #%d, Speed %s, Width x%d, ASPM %s",
>         t >> 24,
>         link_speed(t & PCI_EXP_LNKCAP_SPEED), (t & PCI_EXP_LNKCAP_WIDTH) >> 4,
> -       aspm_support((t & PCI_EXP_LNKCAP_ASPM) >> 10),
> -       latency_l0s((t & PCI_EXP_LNKCAP_L0S) >> 12),
> +       aspm_support(aspm));
> +  if (aspm & 1)
> +    printf(", L0s Exit Latency %s",

Note that this changes the text from "Exit Latency L0s" to "L0s Exit Latency".

> +       latency_l0s((t & PCI_EXP_LNKCAP_L0S) >> 12));
> +  if (aspm & 2)
> +    printf(", L1 Exit Latency %s",

It also changes this from "L1" to "L1 Exit Latency".  I added "Exit
Latency" because it's now possible to print this part without the
"L0s" part.

But this all makes the line longer and changes text that scripts could
be parsing, so I understand if you object.

Along this line, cap_express_dev() prints "Latency L0s %s" when it
decodes what the spec calls "L0s Acceptable Latency".  Maybe it would
be useful to include "Acceptable"?

>         latency_l1((t & PCI_EXP_LNKCAP_L1) >> 15));
> +  printf("\n");
>    printf("\t\t\tClockPM%c Surprise%c LLActRep%c BwNot%c ASPMOptComp%c\n",
>         FLAG(t, PCI_EXP_LNKCAP_CLOCKPM),
>         FLAG(t, PCI_EXP_LNKCAP_SURPRISE),
>
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