Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Ian Dannapel <iansdannapel@gmail.com>
To:     linux@rempel-privat.de
Cc:     kernel@pengutronix.de, shawnguo@kernel.org, s.hauer@pengutronix.de,
        festevam@gmail.com, linux-imx@nxp.com, linux-i2c@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Michael.Glembotzki@iris-sensing.com,
        Erik.Schumacher@iris-sensing.com,
        Ian Dannapel <iansdannapel@gmail.com>
Subject: [PATCH] i2c: imx: remove unnecessary delay at startup
Date:   Mon, 14 Mar 2022 10:59:18 +0100
Message-Id: <20220314095918.50014-1-iansdannapel@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Precedence: bulk

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@gmail.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