From: Vinod Koul <vkoul@kernel.org>
To: Pierre Yves MORDRET <pierre-yves.mordret@st.com>
Cc: Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexandre Torgue <alexandre.torgue@st.com>,
Maxime Coquelin <mcoquelin.stm32@gmail.com>,
Dan Williams <dan.j.williams@intel.com>,
devicetree@vger.kernel.org, dmaengine@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: [v3,1/7] dt-bindings: stm32-dma: Add DMA/MDMA chaining support bindings
Date: Tue, 9 Oct 2018 14:27:57 +0530 [thread overview]
Message-ID: <20181009085757.GI2372@vkoul-mobl> (raw)
Hi Pierre,
On 09-10-18, 09:18, Pierre Yves MORDRET wrote:
> >> * DMA client
> >> @@ -68,7 +84,16 @@ channel: a phandle to the DMA controller plus the following four integer cells:
> >> 0x1: 1/2 full FIFO
> >> 0x2: 3/4 full FIFO
> >> 0x3: full FIFO
> >> -
> >> + -bit 2: Intermediate M2M transfer from/to DDR to/from SRAM throughout MDMA
> >> + 0: MDMA not used to generate an intermediate M2M transfer
> >> + 1: MDMA used to generate an intermediate M2M transfer.
> >> + -bit 3-4: indicated SRAM Buffer size in (2^order)*PAGE_SIZE.
> >> + PAGE_SIZE is given by Linux at 4KiB: include/asm-generic/page.h.
> >> + Order is given by those 2 bits starting at 0.
> >> + Valid only whether Intermediate M2M transfer is set.
> >
> > why do we need this as a property?
>
> In some UC, we need more than 4KiB in case of chaining for better performances.
> Chaining has to be enabled by client if performance is at sacks.
Okay if that is the case why is the user not taking care of this?
Creating DMA txn and chaining them up and starting the chain? Why would
dmaengine driver need to do that?
next reply other threads:[~2018-10-09 8:57 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-09 8:57 Vinod Koul [this message]
-- strict thread matches above, loose matches on Subject: below --
2018-10-12 14:42 [v3,1/7] dt-bindings: stm32-dma: Add DMA/MDMA chaining support bindings Rob Herring
2018-10-09 13:46 Pierre Yves MORDRET
2018-10-09 7:18 Pierre Yves MORDRET
2018-10-07 14:57 Vinod Koul
2018-09-28 13:01 Pierre Yves MORDRET
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