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	2017-03-01 17:00 +0100
Message-ID	<tgePx-5b2-31@gated-at.bofh.it> (permalink)
References	(2 earlier) <tfXOG-1BX-11@gated-at.bofh.it> <tg7l0-8hz-19@gated-at.bofh.it> <tgaiR-2ds-7@gated-at.bofh.it> <tgbHY-334-23@gated-at.bofh.it> <tgdqp-4gi-3@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 Wed, Mar 01, 2017 at 03:21:24PM +0100, Cyrille Pitchen wrote:

> Besides, some SPI controller drivers may already use their own bounce
> buffer for other reasons. Then for those controllers, it would be one
> more copy.

They probably shouldn't, there's a lot of legacy drivers that do all
sorts of fun stuff but if people are having performance problems we
should probably be putting pressure on the driver users to improve
things.  Anything that has a bounce buffer probably isn't going to say
it can do DMA though...

> Then I don't whether we should:
> 1 -  extend in SPI sub-system API to tell us if the SPI controller can
> deal with non-kmalloc'd buffer for DMA transfers

I don't think we can tell any better than anything else really.  We
could tell if a driver has a bounce buffer or is PIO based but that's
not the whole story so it's not ideal.

> or

> 2 - get the answer at a system-wide level.

That seems better.  It'd be really good if we had a function we could
call that'd do the mappings including any bounce buffering that's needed
rather than having to think about it in the subsystems.

Thread

[RFC PATCH 0/2] mtd: spi-nor: Handle vmalloc'd buffers Vignesh R <vigneshr@ti.com> - 2017-02-27 13:20 +0100
  [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce buffer support Vignesh R <vigneshr@ti.com> - 2017-02-27 13:20 +0100
    Re: [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce  buffer support Richard Weinberger <richard@nod.at> - 2017-02-28 22:50 +0100
      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
  [RFC PATCH 1/2] mtd: spi-nor: Introduce bounce buffer to handle vmalloc'd buffers Vignesh R <vigneshr@ti.com> - 2017-02-27 13:20 +0100
    Re: [RFC PATCH 1/2] mtd: spi-nor: Introduce bounce buffer to handle  vmalloc'd buffers Richard Weinberger <richard@nod.at> - 2017-03-01 02:50 +0100
      Re: [RFC PATCH 1/2] mtd: spi-nor: Introduce bounce buffer to handle  vmalloc'd buffers Vignesh R <vigneshr@ti.com> - 2017-03-01 09:00 +0100
      Re: [RFC PATCH 1/2] mtd: spi-nor: Introduce bounce buffer to handle  vmalloc'd buffers Cyrille Pitchen <cyrille.pitchen@atmel.com> - 2017-03-01 11:20 +0100
        Re: [RFC PATCH 1/2] mtd: spi-nor: Introduce bounce buffer to handle  vmalloc'd buffers Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-03-01 12:00 +0100
          Re: [RFC PATCH 1/2] mtd: spi-nor: Introduce bounce buffer to handle  vmalloc'd buffers Frode Isaksen <fisaksen@baylibre.com> - 2017-03-01 12:30 +0100
            Re: [RFC PATCH 1/2] mtd: spi-nor: Introduce bounce buffer to handle  vmalloc'd buffers Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-03-01 13:40 +0100
        Re: [RFC PATCH 1/2] mtd: spi-nor: Introduce bounce buffer to handle  vmalloc'd buffers Vignesh R <vigneshr@ti.com> - 2017-03-01 13:00 +0100
  Re: [RFC PATCH 0/2] mtd: spi-nor: Handle vmalloc'd buffers Frode Isaksen <fisaksen@baylibre.com> - 2017-02-27 17:00 +0100

csiph-web