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Date:	Thu, 06 Feb 2014 14:31:16 +0100
From:	Tomasz Figa <t.figa@...sung.com>
To:	Naveen Krishna Chatradhi <ch.naveen@...sung.com>,
	linux-samsung-soc@...r.kernel.org, linux-i2c@...r.kernel.org
Cc:	linux-arm-kernel@...ts.infradead.org,
	devicetree-discuss@...ts.ozlabs.org, naveenkrishna.ch@...il.com,
	kgene.kim@...sung.com, grant.likely@...retlab.ca,
	w.sang@...gutronix.de, linux-kernel@...r.kernel.org,
	taeggyun.ko@...sung.com, balbi@...com, cpgs@...sung.com
Subject: Re: [PATCH 1/2 v3] i2c: exynos5: add support for HSI2C on Exynos5260
 SoC

Hi Naveen,

On 06.02.2014 13:06, Naveen Krishna Chatradhi wrote:
> This patch implements a variant struct to handle the differences
> (like fifo_depths) in the HSI2C modules across SoCs.
>
> Adds a new compatible to support HSI2C module on Exynos5260.
> Also resets the module as an init sequence (Needed by Exynos5260).
>
> Signed-off-by: Naveen Krishna Chatradhi <ch.naveen@...sung.com>
> ---
> Changes since v2:
> 1. Used variant struct as suggested by Tomasz Figa.
> 2. Change compatible strings from samsung,exynos5-hsi2c to
>     samsung,exynos5250-hsi2c based on the first SoC to see the feature.
> 3. Using reset as init sequences.
> 4. Merged the 2 patches into one.
>
>   .../devicetree/bindings/i2c/i2c-exynos5.txt        |    8 ++-
>   drivers/i2c/busses/i2c-exynos5.c                   |   64 ++++++++++++++++----
>   2 files changed, 58 insertions(+), 14 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-exynos5.txt b/Documentation/devicetree/bindings/i2c/i2c-exynos5.txt
> index 056732c..5bc4998 100644
> --- a/Documentation/devicetree/bindings/i2c/i2c-exynos5.txt
> +++ b/Documentation/devicetree/bindings/i2c/i2c-exynos5.txt
> @@ -5,7 +5,11 @@ at various speeds ranging from 100khz to 3.4Mhz.
>
>   Required properties:
>     - compatible: value should be.
> -      -> "samsung,exynos5-hsi2c", for i2c compatible with exynos5 hsi2c.

Device tree bindings need to be backwards compatible, so you need to 
keep this compatible string supported, just marked as (DEPRECATED).

Driver-wise, it will use the same driver data / variant struct as 
"samsung,exynos5250-hsi2c", just one more entry in OF match table is needed.

> +	-> "samsung,exynos5250-hsi2c", for i2c compatible with HSI2C available
> +				on Exynos5250 and Exynos5420 SoCs.
> +	-> "samsung,exynos5260-hsi2c", for i2c compatible with HSI2C available
> +				on Exynos5260 SoCs.
> +
>     - reg: physical base address of the controller and length of memory mapped
>       region.
>     - interrupts: interrupt number to the cpu.
> @@ -26,7 +30,7 @@ Optional properties:
>   Example:
>
>   hsi2c@...a0000 {
> -	compatible = "samsung,exynos5-hsi2c";
> +	compatible = "samsung,exynos5250-hsi2c";
>   	reg = <0x12ca0000 0x100>;
>   	interrupts = <56>;
>   	clock-frequency = <100000>;

[snip]

> @@ -483,6 +514,7 @@ static void exynos5_i2c_message_start(struct exynos5_i2c *i2c, int stop)
>   	u32 i2c_auto_conf = 0;
>   	u32 fifo_ctl;
>   	unsigned long flags;
> +	unsigned short trig_lvl;
>
>   	i2c_ctl = readl(i2c->regs + HSI2C_CTL);
>   	i2c_ctl &= ~(HSI2C_TXCHON | HSI2C_RXCHON);
> @@ -493,13 +525,19 @@ static void exynos5_i2c_message_start(struct exynos5_i2c *i2c, int stop)
>
>   		i2c_auto_conf = HSI2C_READ_WRITE;
>
> -		fifo_ctl |= HSI2C_RXFIFO_TRIGGER_LEVEL(HSI2C_DEF_TXFIFO_LVL);
> +		trig_lvl = (i2c->msg->len > i2c->variant->fifo_depth) ?
> +			(i2c->variant->fifo_depth * 3/4) : i2c->msg->len;
> +		fifo_ctl |= HSI2C_RXFIFO_TRIGGER_LEVEL(trig_lvl);
> +

This is a rather serious semantic change, that doesn't look to belong to 
this patch. If this is needed, it should be done in a separate patch.

>   		int_en |= (HSI2C_INT_RX_ALMOSTFULL_EN |
>   			HSI2C_INT_TRAILING_EN);
>   	} else {
>   		i2c_ctl |= HSI2C_TXCHON;
>
> -		fifo_ctl |= HSI2C_TXFIFO_TRIGGER_LEVEL(HSI2C_DEF_RXFIFO_LVL);
> +		trig_lvl = (i2c->msg->len > i2c->variant->fifo_depth) ?
> +			(i2c->variant->fifo_depth * 1/4) : i2c->msg->len;
> +		fifo_ctl |= HSI2C_TXFIFO_TRIGGER_LEVEL(trig_lvl);
> +

Ditto.

Best regards,
Tomasz
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