From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Shevchenko Subject: Re: [PATCH v1 0/2] spi: dw-mid: fix simplex DMA transfers Date: Thu, 30 Oct 2014 09:10:54 +0200 Message-ID: <1414653054.2396.66.camel@linux.intel.com> References: <1414513502-595-1-git-send-email-andriy.shevchenko@linux.intel.com> <20141028224156.GN18557@sirena.org.uk> <1414579076.2396.62.camel@linux.intel.com> <20141029111712.GE18557@sirena.org.uk> <1414588848.2396.64.camel@linux.intel.com> <20141029221530.GQ18557@sirena.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Mark Brown Return-path: In-Reply-To: <20141029221530.GQ18557-GFdadSzt00ze9xe1eoZjHA@public.gmane.org> Sender: linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: On Wed, 2014-10-29 at 22:15 +0000, Mark Brown wrote: > On Wed, Oct 29, 2014 at 03:20:48PM +0200, Andy Shevchenko wrote: > > On Wed, 2014-10-29 at 11:17 +0000, Mark Brown wrote: >=20 > > > - how exactly has this been tested? =20 >=20 > > I don't know how it was tested before, but, besides intel-mid-dma i= s > > somehow broken (I won't spend time to patch it), I'm using patch I > > already published which converts driver to use dw_dmac driver. With= it I > > run tests on a loop back. >=20 > How exactly do you run those tests though, what is the client driver? I have a hack patch to register the spidev and I run internal test suit= e written by Mika Westerberg. It uses a loop back mode to send and check data. >=20 > > > tx_dma and rx_dma > > > *can* be provided by users but vanishingly few actually do so. D= rivers > > > must not rely on the caller doing this, the feature will be going= away > > > apart from anything else. If the driver is relying on this it pr= obably > > > needs to have the DMA support that's there removed as a fix and s= hould > > > be converted to use the core DMA mapping functionality in -next. >=20 > > So, regarding to above what would you like me to do as next step? >=20 > Looking at map_dma_buffers() it's probably actually safe since it che= cks > that the message has is_dma_mapped set which virtually no clients wil= l > do. However this means that we're not bothering to DMA almost all th= e > time which is silly - I'd like to see the driver converted to provide= a > can_dma() operation and let the core worry about mapping, that will m= ean > a substantial performance win for most clients. That is exactly my intention with the additional thing =E2=80=94 to use= dw_dmac instead of intel-mid-dma. --=20 Andy Shevchenko Intel Finland Oy -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html