linux-kernel - [PATCH v4 0/5] spi: spi-geni-qcom: Fixes / perf improvements

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Message-Id: <20200618150626.237027-1-dianders@chromium.org>
Date:   Thu, 18 Jun 2020 08:06:21 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     swboyd@...omium.org, Alok Chauhan <alokc@...eaurora.org>,
        skakit@...eaurora.org, Douglas Anderson <dianders@...omium.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Dilip Kota <dkota@...eaurora.org>,
        Girish Mahadevan <girishm@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-spi@...r.kernel.org
Subject: [PATCH v4 0/5] spi: spi-geni-qcom: Fixes / perf improvements

This patch series is a new version of the previous patch posted:
  [PATCH v2] spi: spi-geni-qcom: Speculative fix of "nobody cared" about interrupt
  https://lore.kernel.org/r/20200317133653.v2.1.I752ebdcfd5e8bf0de06d66e767b8974932b3620e@changeid

At this point I've done enough tracing to know that there was a real
race in the old code (not just weakly ordered memory problems) and
that should be fixed with the locking patches.

While looking at this driver, I also noticed we weren't properly
noting error interrupts and also weren't actually using our FIFO
effectively, so I fixed those.

The last patch in the series addresses review feedback about dislike
for the "cur_mcmd" state variable.  It also could possibly make
"abort" work ever-so-slightly more reliably.

Changes in v4:
- Drop 'controller' in comment.
- Use Stephen's diagram to explain the race better.

Changes in v3:
- ("spi: spi-geni-qcom: No need for irqsave variant...") new for v3
- Split out some lock cleanup to previous patch.
- Don't need to read IRQ status register inside spinlock.
- Don't check for state CMD_NONE; later patch is removing state var.
- Don't hold the lock for all of setup_fifo_xfer().
- Comment about why it's safe to Ack interrupts at the end.
- Subject/desc changed since race is definitely there.
- ("spi: spi-geni-qcom: Check for error IRQs") new in v3.
- ("spi: spi-geni-qcom: Actually use our FIFO") new in v3.
- ("spi: spi-geni-qcom: Don't keep a local state variable") new in v3.

Changes in v2:
- Detect true spurious interrupt.
- Still return IRQ_NONE for state machine mismatch, but print warn.

Douglas Anderson (5):
  spi: spi-geni-qcom: No need for irqsave variant of spinlock calls
  spi: spi-geni-qcom: Mo' betta locking
  spi: spi-geni-qcom: Check for error IRQs
  spi: spi-geni-qcom: Actually use our FIFO
  spi: spi-geni-qcom: Don't keep a local state variable

 drivers/spi/spi-geni-qcom.c | 120 ++++++++++++++++++++++++------------
 1 file changed, 81 insertions(+), 39 deletions(-)

-- 
2.27.0.290.gba653c62da-goog