linux-kernel - [PATCH v2 00/32] dmaengine: at_hdmac: Fix concurrency bugs and then convert to virt-dma

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Message-ID: <20221025090306.297886-1-tudor.ambarus@microchip.com>
Date:   Tue, 25 Oct 2022 12:02:34 +0300
From:   Tudor Ambarus <tudor.ambarus@...rochip.com>
To:     <vkoul@...nel.org>, <peda@...ntia.se>, <du@...ntia.se>
CC:     <maciej.sosnowski@...el.com>, <nicolas.ferre@...rochip.com>,
        <mripard@...nel.org>, <torfl6749@...il.com>,
        <linux-kernel@...r.kernel.org>, <dmaengine@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        "Tudor Ambarus" <tudor.ambarus@...rochip.com>
Subject: [PATCH v2 00/32] dmaengine: at_hdmac: Fix concurrency bugs and then convert to virt-dma

v2:
- reorder patches so that fixes come first -> easier to backport to
stable kernels.
- drop the devm_request_irq() patch as we had to disable the irq anyway
in remove() in order to avoid spurios IRQs. Using devm variant brings no
palpable benefit.
- reword pm_ptr commit message


at_hdmac driver had poor list handling and concurrency bugs.
We experienced calling of the completion call twice for the
same descriptor. Peter Rosin encountered the same while
reporting a different bug:
https://lore.kernel.org/lkml/13c6c9a2-6db5-c3bf-349b-4c127ad3496a@axentia.se/

Two sets of tests were performed:
1/ tested just the fixes, to make sure everything is fine and the
concurrency bugs are squashed even without the conversion to virt-dma.
All went fine.
2/ tested the entire series including the conversion the virt-dma
All went fine.

I tested NAND (prep_dma_memcpy), MMC (prep_dma_slave_sg),
usart (cyclic mode), dmatest (memcpy, memset).
With the conversion to virt-dma I replaced the election of a new transfer
in the tasklet with the election of the new transfer in the interrupt
handler. We should have a shorter idle window as we remove the scheduling
latency of the tasklet. Using mtd_speedtest showed similar performances
when using NAND with DMA. That could be because of using a low timming
mode on NAND.


Tudor Ambarus (32):
  dmaengine: at_hdmac: Fix at_lli struct definition
  dmaengine: at_hdmac: Don't start transactions at tx_submit level
  dmaengine: at_hdmac: Start transfer for cyclic channels in
    issue_pending
  dmaengine: at_hdmac: Fix premature completion of desc in issue_pending
  dmaengine: at_hdmac: Do not call the complete callback on
    device_terminate_all
  dmaengine: at_hdmac: Protect atchan->status with the channel lock
  dmaengine: at_hdmac: Fix concurrency problems by removing
    atc_complete_all()
  dmaengine: at_hdmac: Fix concurrency over descriptor
  dmaengine: at_hdmac: Free the memset buf without holding the chan lock
  dmaengine: at_hdmac: Fix concurrency over the active list
  dmaengine: at_hdmac: Fix descriptor handling when issuing it to
    hardware
  dmaengine: at_hdmac: Fix completion of unissued descriptor in case of
    errors
  dmaengine: at_hdmac: Don't allow CPU to reorder channel enable
  dmaengine: at_hdmac: Fix impossible condition
  dmaengine: at_hdmac: Check return code of dma_async_device_register
  dmaengine: at_hdmac: Do not print messages on console while holding
    the lock
  dmaengine: at_hdmac: Return dma_cookie_status()'s ret code when
    txstate is NULL
  dmaengine: at_hdmac: Remove superfluous cast
  dmaengine: at_hdmac: Pass residue by address to avoid unnecessary
    implicit casts
  dmaengine: at_hdmac: s/atc_get_bytes_left/atc_get_residue
  dmaengine: at_hdmac: Introduce atc_get_llis_residue()
  dmaengine: at_hdmac: Use devm_kzalloc() and struct_size()
  dmaengine: at_hdmac: Use devm_platform_ioremap_resource
  dmaengine: at_hdmac: Use devm_clk_get()
  dmaengine: at_hdmac: Use pm_ptr()
  dmaengine: at_hdmac: Set include entries in alphabetic order
  dmaengine: at_hdmac: Keep register definitions and structures private
    to at_hdmac.c
  dmaengine: at_hdmac: Use bitfield access macros
  dmaengine: at_hdmac: Rename "dma_common" to "dma_device"
  dmaengine: at_hdmac: Rename "chan_common" to "dma_chan"
  dmaengine: at_hdmac: Remove unused member of at_dma_chan
  dmaengine: at_hdmac: Convert driver to use virt-dma

 MAINTAINERS                 |    1 -
 drivers/dma/Kconfig         |    1 +
 drivers/dma/at_hdmac.c      | 1899 ++++++++++++++++++-----------------
 drivers/dma/at_hdmac_regs.h |  478 ---------
 4 files changed, 990 insertions(+), 1389 deletions(-)
 delete mode 100644 drivers/dma/at_hdmac_regs.h

-- 
2.25.1