Re: [Intel-wired-lan] [PATCH iwl-net v1 1/1] igc: Correct the short interval between PTM requests.

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On 7/18/2023 19:45, Bjorn Helgaas wrote:
[+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

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(),

   /* 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 |

   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  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

I know. This is a different problem. (I can not reproduce, we will try to get HP dock). We will think how to help here.

  #define IGC_PTM_CYC_TIME_DEFAULT	5   /* Default PTM cycle time */
  #define IGC_PTM_TIMEOUT_DEFAULT		255 /* Default timeout for PTM errors */

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