linux-kernel - Re: [PATCH v2 1/2] i2c: mediatek: Reset DMA engine in hardware init function

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Message-ID: <CAGS+omAXRz5obq3si1tOdT5JSLB6m8XcdaN2VGpaLbuqMyqVGw@mail.gmail.com>
Date:	Tue, 11 Aug 2015 16:32:38 +0800
From:	Daniel Kurtz <djkurtz@...omium.org>
To:	Eddie Huang <eddie.huang@...iatek.com>
Cc:	Wolfram Sang <wsa@...-dreams.de>,
	srv_heupstream <srv_heupstream@...iatek.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Liguo Zhang <liguo.zhang@...iatek.com>,
	Xudong Chen <xudong.chen@...iatek.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Linux I2C <linux-i2c@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v2 1/2] i2c: mediatek: Reset DMA engine in hardware init function

On Thu, Aug 6, 2015 at 3:22 PM, Eddie Huang <eddie.huang@...iatek.com> wrote:
> Reset DMA in hardware init function to avoid unknown hardware state
> before do any I2C operation.
>
> Signed-off-by: Liguo Zhang <liguo.zhang@...iatek.com>
> Signed-off-by: Eddie Huang <eddie.huang@...iatek.com>

Reviewed-by: Daniel Kurtz <djkurtz@...omium.org>

> ---
>  drivers/i2c/busses/i2c-mt65xx.c |    6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
> index 9920eef..e28ad4c 100644
> --- a/drivers/i2c/busses/i2c-mt65xx.c
> +++ b/drivers/i2c/busses/i2c-mt65xx.c
> @@ -59,6 +59,7 @@
>  #define I2C_DMA_START_EN               0x0001
>  #define I2C_DMA_INT_FLAG_NONE          0x0000
>  #define I2C_DMA_CLR_FLAG               0x0000
> +#define I2C_DMA_HARD_RST               0x0002
>
>  #define I2C_DEFAULT_SPEED              100000  /* hz */
>  #define MAX_FS_MODE_SPEED              400000
> @@ -81,6 +82,7 @@ enum DMA_REGS_OFFSET {
>         OFFSET_INT_FLAG = 0x0,
>         OFFSET_INT_EN = 0x04,
>         OFFSET_EN = 0x08,
> +       OFFSET_RST = 0x0c,
>         OFFSET_CON = 0x18,
>         OFFSET_TX_MEM_ADDR = 0x1c,
>         OFFSET_RX_MEM_ADDR = 0x20,
> @@ -262,6 +264,10 @@ static void mtk_i2c_init_hw(struct mtk_i2c *i2c)
>                       I2C_CONTROL_CLK_EXT_EN | I2C_CONTROL_DMA_EN;
>         writew(control_reg, i2c->base + OFFSET_CONTROL);
>         writew(I2C_DELAY_LEN, i2c->base + OFFSET_DELAY_LEN);
> +
> +       writel(I2C_DMA_HARD_RST, i2c->pdmabase + OFFSET_RST);
> +       udelay(50);
> +       writel(I2C_DMA_CLR_FLAG, i2c->pdmabase + OFFSET_RST);
>  }
>
>  /*
> --
> 1.7.9.5
>
> --
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