linux-kernel - Re: [PATCH] i2c: imx: remove unnecessary delay at startup

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Date:   Mon, 14 Mar 2022 11:13:37 +0100
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Ian Dannapel <iansdannapel@...il.com>
Cc:     linux@...pel-privat.de, Erik.Schumacher@...s-sensing.com,
        shawnguo@...nel.org, s.hauer@...gutronix.de,
        linux-kernel@...r.kernel.org, Michael.Glembotzki@...s-sensing.com,
        linux-imx@....com, kernel@...gutronix.de, festevam@...il.com,
        linux-arm-kernel@...ts.infradead.org, linux-i2c@...r.kernel.org
Subject: Re: [PATCH] i2c: imx: remove unnecessary delay at startup

Hello,

On Mon, Mar 14, 2022 at 10:59:18AM +0100, Ian Dannapel wrote:
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index 3576b63a6c03..019dda5301df 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -602,12 +602,6 @@ static int i2c_imx_start(struct imx_i2c_struct *i2c_imx, bool atomic)
>  	imx_i2c_write_reg(i2c_imx->hwdata->i2sr_clr_opcode, i2c_imx, IMX_I2C_I2SR);
>  	imx_i2c_write_reg(i2c_imx->hwdata->i2cr_ien_opcode, i2c_imx, IMX_I2C_I2CR);
>  
> -	/* Wait controller to be stable */
> -	if (atomic)
> -		udelay(50);
> -	else
> -		usleep_range(50, 150);
> -
>  	/* Start I2C transaction */
>  	temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
>  	temp |= I2CR_MSTA;

This contradicts statements made in
43309f3b521302bb66c4c9e66704dd3675e4d725.

Maybe the sleep/delay should be done conditionally on the busy bit?

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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