[+cc Paul, Vinicius, Kai-Heng, Guilherme]
On Mon, Jul 17, 2023 at 08:19:27PM +0300, Sasha Neftin wrote:
> With the 10us interval, we were seeing PTM transactions taking around 12us.
> With the 1us interval, PTM dialogs took around 2us. Checked with the PCIe
> sniffer.
>
> Fixes: a90ec8483732 ("igc: Add support for PTP getcrosststamp()")
> Suggested-by: Vinicius Costa Gomes <vinicius.gomes@xxxxxxxxx>
> Signed-off-by: Sasha Neftin <sasha.neftin@xxxxxxxxx>
> ---
> drivers/net/ethernet/intel/igc/igc_defines.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/igc/igc_defines.h b/drivers/net/ethernet/intel/igc/igc_defines.h
> index 44a507029946..c3722f524ea7 100644
> --- a/drivers/net/ethernet/intel/igc/igc_defines.h
> +++ b/drivers/net/ethernet/intel/igc/igc_defines.h
> @@ -549,7 +549,7 @@
> #define IGC_PTM_CTRL_SHRT_CYC(usec) (((usec) & 0x2f) << 2)
> #define IGC_PTM_CTRL_PTM_TO(usec) (((usec) & 0xff) << 8)
>
> -#define IGC_PTM_SHORT_CYC_DEFAULT 10 /* Default Short/interrupted cycle interval */
> +#define IGC_PTM_SHORT_CYC_DEFAULT 1 /* Default short cycle interval */
Not related to *this* patch, but from looking at igc_ptp_reset(),
where IGC_PTM_SHORT_CYC_DEFAULT is used,
/* PCIe PTM Control */
#define IGC_PTM_CTRL_START_NOW BIT(29) /* Start PTM Now */
#define IGC_PTM_CTRL_EN BIT(30) /* Enable PTM */
ctrl = IGC_PTM_CTRL_EN |
IGC_PTM_CTRL_START_NOW |
IGC_PTM_CTRL_SHRT_CYC(IGC_PTM_SHORT_CYC_DEFAULT) |
IGC_PTM_CTRL_PTM_TO(IGC_PTM_TIMEOUT_DEFAULT) |
IGC_PTM_CTRL_TRIG;
wr32(IGC_PTM_CTRL, ctrl);
Obviously this must be implementation-specific PTM configuration,
which is fine. But I assume even though this sets IGC_PTM_CTRL_EN and
IGC_PTM_CTRL_START_NOW, the device will not actually send PTM Request
messages unless the architected PTM Enable bit in the PTM Capability
is set (PCIe r6.0, sec 7.9.15.3). Right?
I'm asking because Kai-Heng has been working on issues where
Unsupported Request errors are reported because some devices seem to
send PTM Requests when we don't think they should. See
https://lore.kernel.org/r/20230714050541.2765246-1-kai.heng.feng@xxxxxxxxxxxxx
> #define IGC_PTM_CYC_TIME_DEFAULT 5 /* Default PTM cycle time */
> #define IGC_PTM_TIMEOUT_DEFAULT 255 /* Default timeout for PTM errors */
