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Message-ID: <20180918235629.GA20199@Mani-XPS-13-9360>
Date: Tue, 18 Sep 2018 16:56:29 -0700
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Vinod <vkoul@...nel.org>
Cc: dan.j.williams@...el.com, afaerber@...e.de, robh+dt@...nel.org,
gregkh@...uxfoundation.org, jslaby@...e.com,
linux-serial@...r.kernel.org, dmaengine@...r.kernel.org,
liuwei@...ions-semi.com, 96boards@...obotics.com,
devicetree@...r.kernel.org, daniel.thompson@...aro.org,
amit.kucheria@...aro.org, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, hzhang@...obotics.com,
bdong@...obotics.com, manivannanece23@...il.com,
thomas.liau@...ions-semi.com, jeff.chen@...ions-semi.com,
pn@...x.de, edgar.righi@...tec.org.br
Subject: Re: [PATCH 2/3] dmaengine: Add Slave and Cyclic mode support for
Actions Semi Owl S900 SoC
On Tue, Sep 18, 2018 at 04:34:14PM -0700, Manivannan Sadhasivam wrote:
> On Tue, Sep 18, 2018 at 04:32:00PM -0700, Vinod wrote:
> > Hi Mani,
> >
> > On 18-09-18, 15:52, Manivannan Sadhasivam wrote:
> > > On Tue, Sep 18, 2018 at 09:35:12AM -0700, Vinod wrote:
> > > > On 01-09-18, 22:12, Manivannan Sadhasivam wrote:
> > > >
> > > > > @@ -364,6 +372,26 @@ static inline int owl_dma_cfg_lli(struct owl_dma_vchan *vchan,
> > > > > OWL_DMA_MODE_DT_DCU | OWL_DMA_MODE_SAM_INC |
> > > > > OWL_DMA_MODE_DAM_INC;
> > > > >
> > > > > + break;
> > > > > + case DMA_MEM_TO_DEV:
> > > > > + mode |= OWL_DMA_MODE_TS(vchan->drq)
> > > > > + | OWL_DMA_MODE_ST_DCU | OWL_DMA_MODE_DT_DEV
> > > > > + | OWL_DMA_MODE_SAM_INC | OWL_DMA_MODE_DAM_CONST;
> > > > > +
> > > > > + /* Handle bus width for UART */
> > > > > + if (sconfig->dst_addr_width == DMA_SLAVE_BUSWIDTH_1_BYTE)
> > > > > + mode |= OWL_DMA_MODE_NDDBW_8BIT;
> > > >
> > > > this is fine per se, but not correct way to handle in dmaengine driver.
> > > > You should be agnostic to user of dmaengine, so handle all the buswidths
> > > > the IP block supports and update the values accordingly. That way new
> > > > uses can be added w/o requiring change in dmaengine driver
> > >
> > > Currently, all members of Owl family supports only 32bit and 8bit
> > > bus widths. 32bit is common for all peripherals and 8bit applies to only
> > > UART since the internal buffer is 8bit wide. So, this makes sense to me!
> >
> > Above you are onky handing DMA_SLAVE_BUSWIDTH_1_BYTE and not 32bit which
> > this IP supports.. You should handle all widths supported vt hardware..
> >
>
> Hi Vinod,
>
> Default width is 32bit and we will only override it for UART... Should I
> add a comment stating this?
>
I think it is better to select 32bit mode eventhough it is the default one.
Will update it in next revision.
Thanks,
Mani
> Thanks,
> Mani
>
> > --
> > ~Vinod
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