linux-kernel - [PATCH 0/2] Fix TX/RX interrupt handling

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Message-ID: <20230310172050.1394-1-mario.limonciello@amd.com>
Date:   Fri, 10 Mar 2023 11:20:48 -0600
From:   Mario Limonciello <mario.limonciello@....com>
To:     Basavaraj Natikar <Basavaraj.Natikar@....com>,
        Sanjay R Mehta <sanju.mehta@....com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        <linux-usb@...r.kernel.org>
CC:     <anson.tsao@....com>,
        Mario Limonciello <mario.limonciello@....com>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH 0/2] Fix TX/RX interrupt handling

Previously a patch series was sent up to change the way that DROM was read
to prefer directly from NVM instead of bit banging.

This series was produced due to issues found where TBT3 DROM CRC wouldn't
match.  In looking at it from USB4 analyzer the DROM wasn't corrupted
before it arrived at the router.  In analyzing the failure mode, every
single failure occurred during a retried TX because RX interrupt
"never came".

This was actually a smoking gun; when the hardware responded too quickly
both TX and RX interrupt status bits were set before the ISR would run.
By the ISR using auto clear on read to process the TX this would make the
RX interrupt bit get lost and the RX interrupt was never handled.

To fix this issue, disable auto clear in the ISR and instead only clear
the interrupt that is actually triggering the ISR.

This fixes the communication for a long series of transactions such as
bit banging and probably also fixes other situations that control transfers
were retried a number of times due to a missing RX.

Mario Limonciello (2):
  thunderbolt: Use const qualifier for `ring_interrupt_index`
  thunderbolt: Disable interrupt auto clear for rings

 drivers/thunderbolt/nhi.c      | 42 +++++++++++++++++++++-------------
 drivers/thunderbolt/nhi_regs.h |  6 +++--
 2 files changed, 30 insertions(+), 18 deletions(-)

-- 
2.25.1