linux-kernel - Re: [PATCH 1/2] i2c: at91: add DT property for the HOLD field of TWIHS

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Message-ID: <560BA4CE.70606@atmel.com>
Date:	Wed, 30 Sep 2015 11:01:02 +0200
From:	Cyrille Pitchen <cyrille.pitchen@...el.com>
To:	Ludovic Desroches <ludovic.desroches@...el.com>,
	<wsa@...-dreams.de>
CC:	<devicetree@...r.kernel.org>, <nicolas.ferre@...el.com>,
	<linux-kernel@...r.kernel.org>,
	Wenyou Yang <wenyou.yang@...el.com>,
	<linux-i2c@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/2] i2c: at91: add DT property for the HOLD field of
 TWIHS_CWGR

Hi all,

it looks good to me.

Le 30/09/2015 10:47, Ludovic Desroches a écrit :
> From: Wenyou Yang <wenyou.yang@...el.com>
> 
> Add the HOLD field setting in order to support I2C slave devices which need
> a longer hold time of the data.
> Since it depends on the slave devices connected to the bus, add a DT
> property "atmel,twd-hold-cycles" to specify this HOLD field.
> 
> Signed-off-by: Wenyou Yang <wenyou.yang@...el.com>
> Signed-off-by: Ludovic Desroches <ludovic.desroches@...el.com>

Acked-by: Cyrille Pitchen <cyrille.pitchen@...el.com>

> ---
>  drivers/i2c/busses/i2c-at91.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
> index 1c758cd..06e66ef 100644
> --- a/drivers/i2c/busses/i2c-at91.c
> +++ b/drivers/i2c/busses/i2c-at91.c
> @@ -64,6 +64,7 @@
>  #define	AT91_TWI_IADR		0x000c	/* Internal Address Register */
>  
>  #define	AT91_TWI_CWGR		0x0010	/* Clock Waveform Generator Reg */
> +#define	AT91_TWI_CWGR_HOLD(x)	(((x) & 0x1f) << 24)
>  
>  #define	AT91_TWI_SR		0x0020	/* Status Register */
>  #define	AT91_TWI_TXCOMP		BIT(0)	/* Transmission Complete */
> @@ -185,7 +186,8 @@ static void at91_init_twi_bus(struct at91_twi_dev *dev)
>   * Calculate symmetric clock as stated in datasheet:
>   * twi_clk = F_MAIN / (2 * (cdiv * (1 << ckdiv) + offset))
>   */
> -static void at91_calc_twi_clock(struct at91_twi_dev *dev, int twi_clk)
> +static void at91_calc_twi_clock(struct at91_twi_dev *dev,
> +				int twi_clk, u32 twd_hold)
>  {
>  	int ckdiv, cdiv, div;
>  	struct at91_twi_pdata *pdata = dev->pdata;
> @@ -204,7 +206,9 @@ static void at91_calc_twi_clock(struct at91_twi_dev *dev, int twi_clk)
>  		cdiv = 255;
>  	}
>  
> -	dev->twi_cwgr_reg = (ckdiv << 16) | (cdiv << 8) | cdiv;
> +	dev->twi_cwgr_reg = (ckdiv << 16) | (cdiv << 8) | cdiv
> +			    | AT91_TWI_CWGR_HOLD(twd_hold);
> +
>  	dev_dbg(dev->dev, "cdiv %d ckdiv %d\n", cdiv, ckdiv);
>  }
>  
> @@ -936,6 +940,7 @@ static int at91_twi_probe(struct platform_device *pdev)
>  	int rc;
>  	u32 phy_addr;
>  	u32 bus_clk_rate;
> +	u32 twd_hold_cycles;
>  
>  	dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_KERNEL);
>  	if (!dev)
> @@ -992,7 +997,12 @@ static int at91_twi_probe(struct platform_device *pdev)
>  	if (rc)
>  		bus_clk_rate = DEFAULT_TWI_CLK_HZ;
>  
> -	at91_calc_twi_clock(dev, bus_clk_rate);
> +	rc = of_property_read_u32(dev->dev->of_node,
> +				  "atmel,twd-hold-cycles", &twd_hold_cycles);
> +	if (rc)
> +		twd_hold_cycles = 0;
> +
> +	at91_calc_twi_clock(dev, bus_clk_rate, twd_hold_cycles);
>  	at91_init_twi_bus(dev);
>  
>  	snprintf(dev->adapter.name, sizeof(dev->adapter.name), "AT91");
> 

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