linux-kernel - Re: [PATCH v10] i2c-designware: make SDA hold time configurable

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Message-ID: <20130703132905.GC3929@ab42.lan>
Date:	Wed, 3 Jul 2013 15:29:06 +0200
From:	Christian Ruppert <christian.ruppert@...lis.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Wolfram Sang <wsa@...-dreams.de>,
	Rob Herring <robherring2@...il.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	linux-i2c@...r.kernel.org,
	"Ben Dooks (embedded platforms)" <ben-linux@...ff.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Landley <rob@...dley.net>,
	devicetree-discuss@...ts.ozlabs.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Vineet Gupta <Vineet.Gupta1@...opsys.com>,
	Pierrick Hascoet <pierrick.hascoet@...lis.com>
Subject: Re: [PATCH v10] i2c-designware: make SDA hold time configurable

On Wed, Jul 03, 2013 at 01:43:11PM +0200, Arnd Bergmann wrote:
> On Wednesday 26 June 2013, Wolfram Sang wrote:
> >   On Wed, Jun 26, 2013 at 10:55:06AM +0200, Christian Ruppert wrote:
> > > This patch makes the SDA hold time configurable through device tree.
> > > 
> > > Signed-off-by: Christian Ruppert <christian.ruppert@...lis.com>
> > > Signed-off-by: Pierrick Hascoet <pierrick.hascoet@...lis.com>
> > 
> > Applied to for-next, thanks for keeping at it and providing lots of
> > useful information. Much appreciated!
> 
> Sorry, but I got a regression that I didn't find reported elsewhere
> so far, even though it breaks a lot of the ARM defconfig builds:
> 
> drivers/built-in.o: In function `dw_i2c_probe':
> /git/arm-soc/drivers/i2c/busses/i2c-designware-platdrv.c:125: undefined reference to `__udivdi3'
> 
> I suspect you want something like the change below.

This looks similar to a patch Vincent Stehle submitted yesterday, see
https://lkml.org/lkml/2013/7/2/145

> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> 
> diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
> index def79b5..57e3a07 100644
> --- a/drivers/i2c/busses/i2c-designware-platdrv.c
> +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
> @@ -119,10 +119,13 @@ static int dw_i2c_probe(struct platform_device *pdev)
>  	if (pdev->dev.of_node) {
>  		u32 ht = 0;
>  		u32 ic_clk = dev->get_clk_rate_khz(dev);
> +		u64 hold_time;
>  
>  		of_property_read_u32(pdev->dev.of_node,
>  					"i2c-sda-hold-time-ns", &ht);
> -		dev->sda_hold_time = ((u64)ic_clk * ht + 500000) / 1000000;
> +		hold_time = (u64)ic_clk * ht + 500000;
> +		do_div(hold_time, 1000000);
> +		dev->sda_hold_time = hold_time;
>  	}
>  
>  	dev->functionality =

-- 
  Christian Ruppert              ,          <christian.ruppert@...lis.com>
                                /|
  Tel: +41/(0)22 816 19-42     //|                 3, Chemin du Pré-Fleuri
                             _// | bilis Systems   CH-1228 Plan-les-Ouates
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