linux-kernel - Re: [PATCH v8] i2c-designware: make SDA hold time configurable

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Date:	Thu, 20 Jun 2013 22:04:54 +0200
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Christian Ruppert <christian.ruppert@...lis.com>
Cc:	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 v8] i2c-designware: make SDA hold time configurable

On Tue, Jun 18, 2013 at 09:44:29AM +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>

Okay, I am convinced of the property now...

> diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
> index 35b70a1..81362e5 100644
> --- a/drivers/i2c/busses/i2c-designware-platdrv.c
> +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
> @@ -34,6 +34,7 @@
>  #include <linux/sched.h>
>  #include <linux/err.h>
>  #include <linux/interrupt.h>
> +#include <linux/of.h>
>  #include <linux/of_i2c.h>
>  #include <linux/platform_device.h>
>  #include <linux/pm.h>
> @@ -121,6 +122,15 @@ static int dw_i2c_probe(struct platform_device *pdev)
>  		return PTR_ERR(dev->clk);
>  	clk_prepare_enable(dev->clk);
>  
> +	if (pdev->dev.of_node) {
> +		u32 ht;
> +		u32 ic_clk = dev->get_clk_rate_khz(dev);
> +
> +		of_property_read_u32(pdev->dev.of_node,
> +					"i2c-sda-hold-time-ns", &ht);
> +		dev->sda_holdO_time = ((u64)ic_clk * ht + 500000) / 1000000;

... but is this correct even if the property is not defined?

> +	}
> +

Thanks for all the input so far!


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