From: Vinod Koul <vinod.koul@intel.com>
To: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: dmaengine@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
Sandeep Nair <sandeep_n@ti.com>,
Russell King <linux@arm.linux.org.uk>,
Grant Likely <grant.likely@linaro.org>,
Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH] dma: Add Keystone Packet DMA Engine driver
Date: Wed, 12 Mar 2014 21:30:17 +0530 [thread overview]
Message-ID: <20140312160017.GY1976@intel.com> (raw)
In-Reply-To: <531F6908.4010104@ti.com>
On Wed, Mar 12, 2014 at 03:50:32AM +0800, Santosh Shilimkar wrote:
> On Tuesday 11 March 2014 06:23 PM, Vinod Koul wrote:
> > On Fri, Feb 28, 2014 at 05:56:40PM -0500, Santosh Shilimkar wrote:
> >> From: Sandeep Nair <sandeep_n@ti.com>
> >>
> >> The Packet DMA driver sets up the dma channels and flows for the
> >> QMSS(Queue Manager SubSystem) who triggers the actual data movements
> >> across clients using destination queues. Every client modules like
> >> NETCP(Network Coprocessor), SRIO(Serial Rapid IO) and CRYPTO
> >> Engines has its own instance of packet dma hardware. QMSS has also
> >> an internal packet DMA module which is used as an infrastructure
> >> DMA with zero copy.
> >>
> >> Patch adds DMAEngine driver for Keystone Packet DMA hardware.
> >> The specifics on the device tree bindings for Packet DMA can be
> >> found in:
> >> Documentation/devicetree/bindings/dma/keystone-pktdma.txt
> >>
> >> The driver implements the configuration functions using standard DMAEngine
> >> apis. The data movement is managed by QMSS device driver.
> > Pls use subsystem appropriate name so here would have been dmaengine: ...
> >
> > So i am still missing stuff like prepare calls, irq, descriptor management to
> > call this a dmaengine driver.
> >
> > I guess you need to explain a bit more why the data movement is handled by some
> > other driver and not by this one
> >
> To expand above statement, Packet DMA hardware blocks on Keystone SOCs
> are DMAEngines. QMSS is centralised subsystem manages multiple functionalities
> including triggering dma transfers, descriptor management and completion
> irqs. There are separate instance of packet DMA hardware block per client
> device. We program the DMA hardware to allocate channels and flows. So
> the packet DMA resouces like dma channels and dma flows are configured
> and managed through the DMAEngine driver. Thats why we implement only
> device_alloc_chan_resources, device_free_chan_resources and device_control
> DMAEngine APIs.
Sorry am bit lost. If its a dmaengine then you still need to program the
transfers, how does that part work?
> >> +#define BITS(x) (BIT(x) - 1)
> > this might get confusing, perhaps a better name could be given?
> >
> Would "BIT_MASK" be ok with you ?
something which would imply its x -1, am not really good with name so no
suggestions :)
> >> +
> >> +#define BUILD_CHECK_REGS() \
> >> + do { \
> >> + BUILD_BUG_ON(sizeof(struct reg_global) != 32); \
> >> + BUILD_BUG_ON(sizeof(struct reg_chan) != 32); \
> >> + BUILD_BUG_ON(sizeof(struct reg_rx_flow) != 32); \
> >> + BUILD_BUG_ON(sizeof(struct reg_tx_sched) != 4); \
> >> + } while (0)
> > why is this required, do you want to use __packed__ to ensure right size?
> >
> This is just to ensure the register sanity. We should use __packed__ as
> well. We can take the BUILD_CHECK_REGS() out if you don't prefer it.
putting packed ensures so no need for this check.
--
~Vinod
next prev parent reply other threads:[~2014-03-12 16:08 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-28 22:56 [PATCH] dma: Add Keystone Packet DMA Engine driver Santosh Shilimkar
2014-02-28 23:14 ` Arnd Bergmann
2014-02-28 23:44 ` Santosh Shilimkar
2014-03-05 2:26 ` Santosh Shilimkar
2014-03-03 9:34 ` Shevchenko, Andriy
2014-03-11 10:23 ` Vinod Koul
2014-03-11 19:50 ` Santosh Shilimkar
2014-03-12 16:00 ` Vinod Koul [this message]
2014-03-12 21:16 ` Santosh Shilimkar
2014-03-17 4:42 ` Vinod Koul
2014-03-17 19:37 ` Santosh Shilimkar
2014-03-18 15:24 ` Vinod Koul
2014-03-18 15:38 ` Arnd Bergmann
2014-03-18 15:51 ` Vinod Koul
2014-03-18 16:22 ` Santosh Shilimkar
2014-03-18 16:40 ` Arnd Bergmann
2014-03-18 16:19 ` Santosh Shilimkar
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