Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1591374

Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce buffer support

From Mark Brown <broonie@kernel.org>
Newsgroups linux.kernel
Subject Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce buffer support
Date 2017-03-02 19:20 +0100
Message-ID <tgDux-67m-1@gated-at.bofh.it> (permalink)
References (5 earlier) <tgbHY-334-23@gated-at.bofh.it> <tgfLA-5N5-7@gated-at.bofh.it> <tguUi-8v7-19@gated-at.bofh.it> <tgAn1-3FV-45@gated-at.bofh.it> <tgAn1-3FV-43@gated-at.bofh.it>
Organization linux.* mail to news gateway

Show all headers | View raw

[Multipart message — attachments visible in raw view] - view raw

On Thu, Mar 02, 2017 at 03:29:21PM +0100, Boris Brezillon wrote:
> Vignesh R <vigneshr@ti.com> wrote:

> > Or SPI core can be extended in a way similar to this RFC. That is, SPI
> > master driver will set a flag to request SPI core to use of bounce
> > buffer for vmalloc'd buffers. And spi_map_buf() just uses bounce buffer
> > in case buf does not belong to kmalloc region based on the flag.

> That's a better approach IMHO. Note that the decision should not only

I don't understand how the driver is supposed to tell if it might need a
bounce buffer due to where the memory is allocated and the caches used
by the particular system it is used on?  The suggestion to pass via
scatterlists seems a bit more likely to work but even then I'm not clear
that drivers doing PIO would play well.

> be based on the buffer type, but also on the transfer length and/or
> whether the controller supports transferring non physically contiguous
> buffers.

The reason most drivers only look at the transfer length when deciding
that they can DMA is that most controllers are paired with DMA
controllers that are sensibly implemented, the only factor they're
selecting on is the copybreak for performance.

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Vignesh R <vigneshr@ti.com> - 2017-03-01 09:00 +0100
  Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Cyrille Pitchen <cyrille.pitchen@atmel.com> - 2017-03-01 12:10 +0100
    Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Frode Isaksen <fisaksen@baylibre.com> - 2017-03-01 12:50 +0100
    Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-03-01 13:40 +0100
    Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-03-01 15:30 +0100
      Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Cyrille Pitchen <cyrille.pitchen@atmel.com> - 2017-03-01 15:40 +0100
    Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Cyrille Pitchen <cyrille.pitchen@atmel.com> - 2017-03-01 15:30 +0100
      Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Mark Brown <broonie@kernel.org> - 2017-03-01 17:00 +0100
    Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-03-01 17:20 +0100
    Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-03-01 18:00 +0100
      Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Frode Isaksen <fisaksen@baylibre.com> - 2017-03-02 10:10 +0100
        Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-03-02 16:00 +0100
          Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Frode Isaksen <fisaksen@baylibre.com> - 2017-03-02 16:20 +0100
            Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-03-02 17:00 +0100
              Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Frode Isaksen <fisaksen@baylibre.com> - 2017-03-03 10:10 +0100
          Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Cyrille Pitchen <cyrille.pitchen@atmel.com> - 2017-03-02 17:50 +0100
          Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Mark Brown <broonie@kernel.org> - 2017-03-02 19:20 +0100
            Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-03-03 04:20 +0100
              Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Mark Brown <broonie@kernel.org> - 2017-03-03 14:20 +0100
          Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Vignesh R <vigneshr@ti.com> - 2017-03-06 12:50 +0100
        Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Vignesh R <vigneshr@ti.com> - 2017-03-03 23:10 +0100

csiph-web