linux-kernel - [PATCH 1/3] [PATCH] af9035: Better explain how i2c bus speed is computed.

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Date:   Thu,  3 Oct 2019 14:45:30 +0200
From:   Gon Solo <gonsolo@...il.com>
To:     mchehab+samsung@...nel.org
Cc:     sean@...s.org, crope@....fi, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org, Gon Solo <gonsolo@...il.com>
Subject: [PATCH 1/3] [PATCH] af9035: Better explain how i2c bus speed is computed.

Original patch from Mauro Carvalho Chehab.

Signed-off-by: Gon Solo <gonsolo@...il.com>
---
 drivers/media/usb/dvb-usb-v2/af9035.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/media/usb/dvb-usb-v2/af9035.c b/drivers/media/usb/dvb-usb-v2/af9035.c
index 3afd18733614..7828f8567da0 100644
--- a/drivers/media/usb/dvb-usb-v2/af9035.c
+++ b/drivers/media/usb/dvb-usb-v2/af9035.c
@@ -1197,6 +1197,9 @@ static int af9035_frontend_attach(struct dvb_usb_adapter *adap)
 	return ret;
 }
 
+/* I2C speed register = (1000000000 / (24.4 * 16 * I2C_speed)) */
+#define I2C_SPEED_REGISTER 7
+
 static int it930x_frontend_attach(struct dvb_usb_adapter *adap)
 {
 	struct state *state = adap_to_priv(adap);
@@ -1208,13 +1211,13 @@ static int it930x_frontend_attach(struct dvb_usb_adapter *adap)
 
 	dev_dbg(&intf->dev, "adap->id=%d\n", adap->id);
 
-	/* I2C master bus 2 clock speed 300k */
-	ret = af9035_wr_reg(d, 0x00f6a7, 0x07);
+	/* I2C master bus 2 clock speed ~300k */
+	ret = af9035_wr_reg(d, 0x00f6a7, I2C_SPEED_REGISTER);
 	if (ret < 0)
 		goto err;
 
-	/* I2C master bus 1,3 clock speed 300k */
-	ret = af9035_wr_reg(d, 0x00f103, 0x07);
+	/* I2C master bus 1,3 clock speed ~300k */
+	ret = af9035_wr_reg(d, 0x00f103, I2C_SPEED_REGISTER);
 	if (ret < 0)
 		goto err;
 
-- 
2.20.1