linux-kernel - RE: [RFC] mmc: msm_sdcc: Use SPS BAM as DMA engine

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Message-ID: <005601cbe9f5$a5088750$ef1995f0$@org>
Date:	Thu, 24 Mar 2011 13:02:31 +0530
From:	"Subhash Jadavani" <subhashj@...eaurora.org>
To:	"'Daniel Walker'" <dwalker@...o99.com>
Cc:	<cjb@...top.org>, <linux-mmc@...r.kernel.org>,
	<linux-arm-msm@...r.kernel.org>, <davidb@...eaurora.org>,
	<bryanh@...eaurora.org>, <linux-kernel@...r.kernel.org>
Subject: RE: [RFC] mmc: msm_sdcc: Use SPS BAM as DMA engine



> -----Original Message-----
> From: linux-mmc-owner@...r.kernel.org [mailto:linux-mmc-
> owner@...r.kernel.org] On Behalf Of Daniel Walker
> Sent: Wednesday, March 23, 2011 6:36 PM
> To: Subhash Jadavani
> Cc: cjb@...top.org; linux-mmc@...r.kernel.org; linux-arm-
> msm@...r.kernel.org; davidb@...eaurora.org; bryanh@...eaurora.org;
> linux-kernel@...r.kernel.org
> Subject: Re: [RFC] mmc: msm_sdcc: Use SPS BAM as DMA engine
> 
> On Fri, 2011-03-18 at 18:54 +0530, Subhash Jadavani wrote:
> > On recent MSMs, ADM (Data Mover) HW is not present
> > which means existing SDCC driver can perform data
> > transfer in PIO (peripheral IO) mode only.
> > But PIO mode requires lot of CPU attention which
> > would mean consuming extra CPU MIPS.
> >
> > As a replacement on these recent MSMs, there is
> > a new DMA HW engine named SPS-BAM (as part of
> > Smart Peripheral System of MSM) is added for
> > data movement between SDCC core and system memory.
> >
> > This patch has done changes in existing MSM SDCC
> > driver for using SPS-BAM as DMA engine.
> 
> 1300+ lines of code might warrant more of a description .. In the
> subject you say "DMA engine" but does this use drivers/dma/dmaengine.c
> ?

Here "DMA engine" means we are using SPS BAM as DMA HW.
No, we are not using the "drivers/dma/dmaengine.c" because MSM SPS driver is not exporting the dma compliant APIs to client. We are using the MSM SPS driver's exported APIs directly from our driver. Not sure what extra description we can put it in commit text. Any suggestion?

This is where MSM SPS driver patch is available: https://patchwork.kernel.org/patch/586271/


> 
> > Signed-off-by: Subhash Jadavani <subhashj@...eaurora.org>
> > ---
> >  drivers/mmc/host/Kconfig        |   10 +
> >  drivers/mmc/host/Makefile       |    1 +
> >  drivers/mmc/host/msm_sdcc.c     |  929
> +++++++++++++++++++++++++++++++++++++--
> >  drivers/mmc/host/msm_sdcc.h     |   47 ++
> >  drivers/mmc/host/msm_sdcc_dml.c |  303 +++++++++++++
> >  drivers/mmc/host/msm_sdcc_dml.h |  120 +++++
> >  6 files changed, 1374 insertions(+), 36 deletions(-)
> >  create mode 100644 drivers/mmc/host/msm_sdcc_dml.c
> >  create mode 100644 drivers/mmc/host/msm_sdcc_dml.h
> 
> I'd do at least two patches. One that adds msm_sdcc_dml.[ch] and one
> that modifies msm_sdcc.[ch] and the Kconfig and Makefile.
> 
> Daniel
> 
> --
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