linux-kernel - Re: [PATCH] ath10k: Add interrupt summary based CE processing

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Date:   Fri, 26 Jun 2020 14:37:46 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Rakesh Pillai <pillair@...eaurora.org>
Cc:     ath10k@...ts.infradead.org,
        linux-wireless <linux-wireless@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ath10k: Add interrupt summary based CE processing

Hi,

On Fri, Jun 26, 2020 at 10:53 AM Rakesh Pillai <pillair@...eaurora.org> wrote:
>
> Currently the NAPI processing loops through all
> the copy engines and processes a particular copy
> engine is the copy completion is set for that copy
> engine. The host driver is not supposed to access
> any copy engine register after clearing the interrupt
> status register.
>
> This might result in kernel crash like the one below
> [ 1159.220143] Call trace:
> [ 1159.220170]  ath10k_snoc_read32+0x20/0x40 [ath10k_snoc]
> [ 1159.220193]  ath10k_ce_per_engine_service_any+0x78/0x130 [ath10k_core]
> [ 1159.220203]  ath10k_snoc_napi_poll+0x38/0x8c [ath10k_snoc]
> [ 1159.220270]  net_rx_action+0x100/0x3b0
> [ 1159.220312]  __do_softirq+0x164/0x30c
> [ 1159.220345]  run_ksoftirqd+0x2c/0x64
> [ 1159.220380]  smpboot_thread_fn+0x1b0/0x288
> [ 1159.220405]  kthread+0x11c/0x12c
> [ 1159.220423]  ret_from_fork+0x10/0x18
>
> To avoid such a scenario, we generate an interrupt
> summary by reading the copy completion for all the
> copy engine before actually processing any of them.
> This will avoid reading the interrupt status register
> for any CE after the interrupt status is cleared.
>
> Tested-on: WCN3990 hw1.0 SNOC WLAN.HL.3.1-01040-QCAHLSWMTPLZ-1
>
> Signed-off-by: Rakesh Pillai <pillair@...eaurora.org>
> ---
>  drivers/net/wireless/ath/ath10k/ce.c | 63 ++++++++++++++++++++++--------------
>  drivers/net/wireless/ath/ath10k/ce.h |  5 +--
>  2 files changed, 42 insertions(+), 26 deletions(-)

I'm not an expert on this driver, but your change seems sane to me.

Reviewed-by: Douglas Anderson <dianders@...omium.org>

With your patch I can no longer find a place to put in a magic delay
and reproduce the crash, thus:

Tested-by: Douglas Anderson <dianders@...omium.org>


If it matters, my WiFi firmware reports this:

WLAN.HL.3.2.2-00490-QCAHLSWMTPL-1

...and it should also be WCN3990.


-Doug