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

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Date:   Tue, 14 Mar 2023 16:28:48 +0200
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Mario Limonciello <mario.limonciello@....com>
Cc:     Basavaraj Natikar <Basavaraj.Natikar@....com>,
        Sanjay R Mehta <sanju.mehta@....com>,
        linux-usb@...r.kernel.org, anson.tsao@....com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] Fix TX/RX interrupt handling

Hi Mario,

On Fri, Mar 10, 2023 at 11:20:48AM -0600, Mario Limonciello wrote:
> 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

Applied both to thunderbolt.git/fixes for v6.3-rc and marked them for
stable as well. Thanks! I dropped the other patch that adjusted the NVM
reading as now it is not necessary anymore (please correct me if I'm
mistaken).