Re: [PATCH v5 0/7] add virt-dma support for imx-sdma
From: Robin Gong
Date: Sun Jul 01 2018 - 22:32:23 EST
Do you have any comment for this patchset? Lucas and Sascha
acked it and tty patch already merged in.
On ä, 2018-06-26 at 17:04 +0200, Lucas Stach wrote:
> Hi Robin,
> I've tested this whole series with the SDMA being used for SPI, UART
> and SSI with no regressions spotted. As this should cover most common
> use-cases, I think this series is good to go in.
> Tested-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> Am Mittwoch, den 20.06.2018, 00:56 +0800 schrieb Robin Gong:
> > The legacy sdma driver has below limitations or drawbacks:
> > Â 1. Hardcode the max BDs number as "PAGE_SIZE / sizeof(*)", and
> > alloc
> > ÂÂÂÂÂone page size for one channel regardless of only few BDs
> > needed
> > ÂÂÂÂÂmost time. But in few cases, the max PAGE_SIZE maybe not
> > enough.
> > Â 2. One SDMA channel can't stop immediatley once channel disabled
> > which
> > ÂÂÂÂÂmeans SDMA interrupt may come in after this channel
> > terminated.There
> > ÂÂÂÂÂare some patches for this corner case such as commit
> > "2746e2c389f9",
> > ÂÂÂÂÂbut not cover non-cyclic.
> > The common virt-dma overcomes the above limitations. It can alloc
> > bd
> > dynamically and free bd once this tx transfer done. No memory
> > wasted or
> > maximum limititation here, only depends on how many memory can be
> > requested
> > from kernel. For No.2, such issue can be workaround by checking if
> > there
> > is available descript("sdmac->desc") now once the unwanted
> > interrupt
> > coming. At last the common virt-dma is easier for sdma driver
> > maintain.
> > Change from v4:
> > Â 1. identify lockdep issue which caused by allocate memory with
> > ÂÂÂÂÂ'GFP_KERNEL', change to 'GFP_NOWAIT' instead so that lockdep
> > ÂÂÂÂÂignore check. That also make sense since Audio/uart driver may
> > ÂÂÂÂÂcall dma function after spin_lock_irqsave()...
> > Â 2. use dma pool instead for bd description allocated,since audio
> > ÂÂÂÂÂdriver may call dma_terminate_all in irq. Please refer to 7/7.
> > Â 3. remove 7/7 serial patch in v4, since lockdep issued fixed by
> > No.1Â
> > Change from v3:
> > Â 1. add two uart patches which impacted by this patchset.
> > Â 2. unlock 'vc.lock' before cyclic dma callback and lock again
> > after
> > ÂÂÂÂÂit because some driver such as uart will call
> > dmaengine_tx_status
> > ÂÂÂÂÂwhich will acquire 'vc.lock' again and dead lock comes out.
> > Â 3. remove 'Revert commit' stuff since that patch is not wrong and
> > ÂÂÂÂÂcombine two patch into one patch as Sascha's comment.
> > Change from v2:
> > Â 1. include Sascha's patch to make the main patch easier to
> > review.
> > ÂÂÂÂÂThanks Sacha.
> > Â 2. remove useless 'desc'/'chan' in struct sdma_channe.
> > Change from v1:
> > Â 1. split v1 patch into 5 patches.
> > Â 2. remove some unnecessary condition check.
> > Â 3. remove unnecessary 'pending' list.
> > Robin Gong (6):
> > Â tty: serial: imx: correct dma cookie status
> > Â dmaengine: imx-sdma: add virt-dma support
> > Â dmaengine: imx-sdma: remove useless 'lock' and 'enabled' in
> > 'struct
> > ÂÂÂÂsdma_channel'
> > Â dmaengine: imx-sdma: remove the maximum limitation for bd numbers
> > Â dmaengine: imx-sdma: add sdma_transfer_init to decrease code
> > overlap
> > Â dmaengine: imx-sdma: alloclate bd memory from dma pool
> > Sascha Hauer (1):
> > Â dmaengine: imx-sdma: factor out a struct sdma_desc from struct
> > ÂÂÂÂsdma_channel
> > Âdrivers/dma/KconfigÂÂÂÂÂÂ|ÂÂÂ1 +
> > Âdrivers/dma/imx-sdma.cÂÂÂ| 400 +++++++++++++++++++++++++++------
> > --------------
> > Âdrivers/tty/serial/imx.c |ÂÂÂ2 +-
> > Â3 files changed, 235 insertions(+), 168 deletions(-)