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From: Marek Vasut <marex@denx.de>
To: Shawn Guo <shawn.guo@linaro.org>
Cc: mark.rutland@arm.com, wsa@the-dreams.de,
	linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Yuan Yao <yao.yuan@freescale.com>
Subject: Re: [PATCH 1/3] i2c: add DMA support for freescale i2c driver
Date: Fri, 28 Feb 2014 09:57:28 +0100	[thread overview]
Message-ID: <201402280957.28985.marex@denx.de> (raw)
In-Reply-To: <20140228022348.GB28660@S2101-09.ap.freescale.net>

On Friday, February 28, 2014 at 03:23:52 AM, Shawn Guo wrote:
> On Fri, Feb 28, 2014 at 10:13:02AM +0800, Shawn Guo wrote:
> > On Thu, Feb 27, 2014 at 09:39:35PM +0100, Marek Vasut wrote:
> > > > @@ -193,6 +216,7 @@ static const struct imx_i2c_hwdata
> > > > imx1_i2c_hwdata  = {
> > > > 
> > > >  	.ndivs			= ARRAY_SIZE(imx_i2c_clk_div),
> > > >  	.i2sr_clr_opcode	= I2SR_CLR_OPCODE_W0C,
> > > >  	.i2cr_ien_opcode	= I2CR_IEN_OPCODE_1,
> > > > 
> > > > +	.has_dma_support	= false,
> > > > 
> > > >  };
> > > > 
> > > > @@ -203,6 +227,7 @@ static const struct imx_i2c_hwdata
> > > > imx21_i2c_hwdata  = { .ndivs			= 
ARRAY_SIZE(imx_i2c_clk_div),
> > > > 
> > > >  	.i2sr_clr_opcode	= I2SR_CLR_OPCODE_W0C,
> > > >  	.i2cr_ien_opcode	= I2CR_IEN_OPCODE_1,
> > > > 
> > > > +	.has_dma_support	= false,
> > > > 
> > > >  };
> > > > 
> > > > @@ -213,6 +238,7 @@ static struct imx_i2c_hwdata vf610_i2c_hwdata = {
> > > > 
> > > >  	.ndivs			= ARRAY_SIZE(vf610_i2c_clk_div),
> > > >  	.i2sr_clr_opcode	= I2SR_CLR_OPCODE_W1C,
> > > >  	.i2cr_ien_opcode	= I2CR_IEN_OPCODE_0,
> > > > 
> > > > +	.has_dma_support	= true,
> > > 
> > > So why exactly don't we have a DT prop for determining whether the
> > > controller has DMA support ?
> > 
> > Using DMA or PIO is a decision that should be made by driver on its own,
> > not device tree.
> 
> Sorry.  I misunderstood it.  Yes, we can look at the DT property 'dmas'
> to know if the controller has DMA capability.

You're right. Whether or not does the hardware support DMA transfers is a 
property of the hardware, that's why it should be in DT.

Best regards,
Marek Vasut

WARNING: multiple messages have this Message-ID (diff)
From: marex@denx.de (Marek Vasut)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/3] i2c: add DMA support for freescale i2c driver
Date: Fri, 28 Feb 2014 09:57:28 +0100	[thread overview]
Message-ID: <201402280957.28985.marex@denx.de> (raw)
In-Reply-To: <20140228022348.GB28660@S2101-09.ap.freescale.net>

On Friday, February 28, 2014 at 03:23:52 AM, Shawn Guo wrote:
> On Fri, Feb 28, 2014 at 10:13:02AM +0800, Shawn Guo wrote:
> > On Thu, Feb 27, 2014 at 09:39:35PM +0100, Marek Vasut wrote:
> > > > @@ -193,6 +216,7 @@ static const struct imx_i2c_hwdata
> > > > imx1_i2c_hwdata  = {
> > > > 
> > > >  	.ndivs			= ARRAY_SIZE(imx_i2c_clk_div),
> > > >  	.i2sr_clr_opcode	= I2SR_CLR_OPCODE_W0C,
> > > >  	.i2cr_ien_opcode	= I2CR_IEN_OPCODE_1,
> > > > 
> > > > +	.has_dma_support	= false,
> > > > 
> > > >  };
> > > > 
> > > > @@ -203,6 +227,7 @@ static const struct imx_i2c_hwdata
> > > > imx21_i2c_hwdata  = { .ndivs			= 
ARRAY_SIZE(imx_i2c_clk_div),
> > > > 
> > > >  	.i2sr_clr_opcode	= I2SR_CLR_OPCODE_W0C,
> > > >  	.i2cr_ien_opcode	= I2CR_IEN_OPCODE_1,
> > > > 
> > > > +	.has_dma_support	= false,
> > > > 
> > > >  };
> > > > 
> > > > @@ -213,6 +238,7 @@ static struct imx_i2c_hwdata vf610_i2c_hwdata = {
> > > > 
> > > >  	.ndivs			= ARRAY_SIZE(vf610_i2c_clk_div),
> > > >  	.i2sr_clr_opcode	= I2SR_CLR_OPCODE_W1C,
> > > >  	.i2cr_ien_opcode	= I2CR_IEN_OPCODE_0,
> > > > 
> > > > +	.has_dma_support	= true,
> > > 
> > > So why exactly don't we have a DT prop for determining whether the
> > > controller has DMA support ?
> > 
> > Using DMA or PIO is a decision that should be made by driver on its own,
> > not device tree.
> 
> Sorry.  I misunderstood it.  Yes, we can look at the DT property 'dmas'
> to know if the controller has DMA capability.

You're right. Whether or not does the hardware support DMA transfers is a 
property of the hardware, that's why it should be in DT.

Best regards,
Marek Vasut

  reply	other threads:[~2014-02-28 10:16 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-02-27  6:05 [PATCH 0/3] i2c: add DMA support for freescale i2c driver Yuan Yao
2014-02-27  6:05 ` Yuan Yao
2014-02-27  6:05 ` Yuan Yao
2014-02-27  6:05 ` [PATCH 1/3] " Yuan Yao
2014-02-27  6:05   ` Yuan Yao
2014-02-27  6:05   ` Yuan Yao
2014-02-27 12:55   ` Shawn Guo
2014-02-27 12:55     ` Shawn Guo
2014-02-27 12:55     ` Shawn Guo
2014-02-27 13:21     ` Shawn Guo
2014-02-27 13:21       ` Shawn Guo
2014-02-27 13:21       ` Shawn Guo
2014-02-27 20:39   ` Marek Vasut
2014-02-27 20:39     ` Marek Vasut
2014-02-27 20:39     ` Marek Vasut
2014-02-28  2:13     ` Shawn Guo
2014-02-28  2:13       ` Shawn Guo
2014-02-28  2:13       ` Shawn Guo
2014-02-28  2:23       ` Shawn Guo
2014-02-28  2:23         ` Shawn Guo
2014-02-28  2:23         ` Shawn Guo
2014-02-28  8:57         ` Marek Vasut [this message]
2014-02-28  8:57           ` Marek Vasut
2014-02-28  5:19     ` Yao Yuan
2014-02-28  5:19       ` Yao Yuan
2014-02-28  5:19       ` Yao Yuan
2014-02-28  9:04       ` Marek Vasut
2014-02-28  9:04         ` Marek Vasut
2014-02-28  9:04         ` Marek Vasut
2014-02-28 10:59         ` Lothar Waßmann
2014-02-28 10:59           ` Lothar Waßmann
2014-02-28 10:59           ` Lothar Waßmann
2014-02-28 12:00           ` Marek Vasut
2014-02-28 12:00             ` Marek Vasut
2014-02-28 12:00             ` Marek Vasut
2014-02-28 11:36         ` Yao Yuan
2014-02-28 11:36           ` Yao Yuan
2014-02-28 11:36           ` Yao Yuan
2014-02-28 12:03           ` Marek Vasut
2014-02-28 12:03             ` Marek Vasut
2014-02-28 12:03             ` Marek Vasut
2014-03-03 10:23     ` Yao Yuan
2014-03-03 10:23       ` Yao Yuan
2014-03-03 10:23       ` Yao Yuan
2014-03-03 11:14       ` Marek Vasut
2014-03-03 11:14         ` Marek Vasut
2014-03-03 11:14         ` Marek Vasut
2014-02-27  6:05 ` [PATCH 3/3] Documentation:add " Yuan Yao
2014-02-27  6:05   ` Yuan Yao
2014-02-27  6:05   ` Yuan Yao

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