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

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Date:   Mon, 14 Mar 2022 10:59:18 +0100
From:   Ian Dannapel <iansdannapel@...il.com>
To:     linux@...pel-privat.de
Cc:     kernel@...gutronix.de, shawnguo@...nel.org, s.hauer@...gutronix.de,
        festevam@...il.com, linux-imx@....com, linux-i2c@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Michael.Glembotzki@...s-sensing.com,
        Erik.Schumacher@...s-sensing.com,
        Ian Dannapel <iansdannapel@...il.com>
Subject: [PATCH] i2c: imx: remove unnecessary delay at startup

a delay on the startup of the i2c imx controller is not required or defined in the specs.
By removing it, the user can see a latency decrease from up to 150μs in communication.
Additional info: https://lore.kernel.org/all/20220304132037.GA15901@pengutronix.de/

Signed-off-by: Ian S. Dannapel <iansdannapel@...il.com>
---
 drivers/i2c/busses/i2c-imx.c | 6 ------
 1 file changed, 6 deletions(-)

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;
-- 
2.25.1