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Re: [PATCH] dma: sun4i: expose block size and wait cycle configuration to DMA users

From Boris Brezillon <boris.brezillon@free-electrons.com>
Newsgroups linux.kernel
Subject Re: [PATCH] dma: sun4i: expose block size and wait cycle configuration to DMA users
Date 2016-03-07 16:10 +0100
Message-ID <ra4Xf-4ss-5@gated-at.bofh.it> (permalink)
References <ra0Ai-1AN-15@gated-at.bofh.it> <ra4NA-49R-29@gated-at.bofh.it>
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Hi Vinod,

On Mon, 7 Mar 2016 20:24:29 +0530
Vinod Koul <vinod.koul@intel.com> wrote:

> On Mon, Mar 07, 2016 at 10:59:31AM +0100, Boris Brezillon wrote:
> > +/* Dedicated DMA parameter register layout */
> > +#define SUN4I_DDMA_PARA_DST_DATA_BLK_SIZE(n)	(((n) - 1) << 24)
> > +#define SUN4I_DDMA_PARA_DST_WAIT_CYCLES(n)	(((n) - 1) << 16)
> > +#define SUN4I_DDMA_PARA_SRC_DATA_BLK_SIZE(n)	(((n) - 1) << 8)
> > +#define SUN4I_DDMA_PARA_SRC_WAIT_CYCLES(n)	(((n) - 1) << 0)
> > +
> > +/**
> > + * struct sun4i_dma_chan_config - DMA channel config
> > + *
> > + * @para: contains information about block size and time before checking
> > + *	  DRQ line. This is device specific and only applicable to dedicated
> > + *	  DMA channels
> 
> What information, can you elobrate.. And why can't you use existing
> dma_slave_config for this?

Block size is related to the device FIFO size. I guess it allows the
DMA channel to launch a transfer of X bytes without having to check the
DRQ line (the line telling the DMA engine it can transfer more data
to/from the device). The wait cycles information is apparently related
to the number of clks the engine should wait before polling/checking
the DRQ line status between each block transfer. I'm not sure what it
saves to put WAIT_CYCLES() to something != 1, but in their BSP,
Allwinner tweak that depending on the device.

Note that I'd be happy if the above configuration could go into the
generic dma_slave_config struct. This way we could avoid per-engine
specific APIs.

Best Regards,

Boris


-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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Thread

[PATCH] dma: sun4i: expose block size and wait cycle configuration to DMA users Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-03-07 11:30 +0100
  Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Vinod Koul <vinod.koul@intel.com> - 2016-03-07 16:00 +0100
    Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-03-07 16:10 +0100
      Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Maxime Ripard <maxime.ripard@free-electrons.com> - 2016-03-07 21:40 +0100
        Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Vinod Koul <vinod.koul@intel.com> - 2016-03-08 04:00 +0100
        Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Vinod Koul <vinod.koul@intel.com> - 2016-03-08 04:00 +0100
          Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Maxime Ripard <maxime.ripard@free-electrons.com> - 2016-03-08 09:00 +0100
            Re: [linux-sunxi] Re: [PATCH] dma: sun4i: expose block size and wait  cycle configuration to DMA users Hans de Goede <hdegoede@redhat.com> - 2016-03-08 09:50 +0100
              Re: [linux-sunxi] Re: [PATCH] dma: sun4i: expose block size and wait  cycle configuration to DMA users Vinod Koul <vinod.koul@intel.com> - 2016-03-08 11:10 +0100
                Re: [linux-sunxi] Re: [PATCH] dma: sun4i: expose block size and wait  cycle configuration to DMA users Maxime Ripard <maxime.ripard@free-electrons.com> - 2016-03-09 12:20 +0100
            Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-03-08 09:50 +0100
              Re: [linux-sunxi] Re: [PATCH] dma: sun4i: expose block size and  wait cycle configuration to DMA users Priit Laes <plaes@plaes.org> - 2016-03-08 10:20 +0100
              Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Vinod Koul <vinod.koul@intel.com> - 2016-03-08 11:10 +0100
              Re: [linux-sunxi] Re: [PATCH] dma: sun4i: expose block size and wait  cycle configuration to DMA users LABBE Corentin <clabbe.montjoie@gmail.com> - 2016-03-09 11:10 +0100
            Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Vinod Koul <vinod.koul@intel.com> - 2016-03-08 11:00 +0100
          Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-03-09 11:20 +0100
            Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Vinod Koul <vinod.koul@intel.com> - 2016-03-11 07:30 +0100
              Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-03-11 10:50 +0100
                Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Vinod Koul <vinod.koul@intel.com> - 2016-03-11 11:10 +0100
                Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-03-11 11:30 +0100
                Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Vinod Koul <vinod.koul@intel.com> - 2016-03-11 12:20 +0100
          Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-03-09 12:30 +0100
            Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Vinod Koul <vinod.koul@intel.com> - 2016-03-11 07:30 +0100
              Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-03-11 10:50 +0100
                Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Vinod Koul <vinod.koul@intel.com> - 2016-03-11 11:10 +0100
                Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Maxime Ripard <maxime.ripard@free-electrons.com> - 2016-03-11 12:00 +0100
                Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Vinod Koul <vinod.koul@intel.com> - 2016-03-11 12:20 +0100
                Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Maxime Ripard <maxime.ripard@free-electrons.com> - 2016-03-14 12:50 +0100
                Re: [PATCH] dma: sun4i: expose block size and wait cycle  configuration to DMA users Vinod Koul <vinod.koul@intel.com> - 2016-03-16 04:20 +0100
  Re: [linux-sunxi] [PATCH] dma: sun4i: expose block size and wait  cycle configuration to DMA users Priit Laes <plaes@plaes.org> - 2016-03-07 16:40 +0100
    Re: [linux-sunxi] [PATCH] dma: sun4i: expose block size and wait  cycle configuration to DMA users Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-03-07 17:00 +0100
      Re: [linux-sunxi] [PATCH] dma: sun4i: expose block size and wait  cycle configuration to DMA users Emilio López <emilio@elopez.com.ar> - 2016-03-07 18:20 +0100

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