linux-kernel - [PATCH 4.9 023/107] i2c: davinci: Avoid zero value of CLKH

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Date:   Mon,  3 Sep 2018 18:55:47 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Alexander Sverdlin <alexander.sverdlin@...ia.com>,
        Sekhar Nori <nsekhar@...com>, Wolfram Sang <wsa@...-dreams.de>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.9 023/107] i2c: davinci: Avoid zero value of CLKH

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alexander Sverdlin <alexander.sverdlin@...ia.com>

[ Upstream commit cc8de9a68599b261244ea453b38678229f06ada7 ]

If CLKH is set to 0 I2C clock is not generated at all, so avoid this value
and stretch the clock in this case.

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@...ia.com>
Acked-by: Sekhar Nori <nsekhar@...com>
Signed-off-by: Wolfram Sang <wsa@...-dreams.de>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/i2c/busses/i2c-davinci.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/drivers/i2c/busses/i2c-davinci.c
+++ b/drivers/i2c/busses/i2c-davinci.c
@@ -234,12 +234,16 @@ static void i2c_davinci_calc_clk_divider
 	/*
 	 * It's not always possible to have 1 to 2 ratio when d=7, so fall back
 	 * to minimal possible clkh in this case.
+	 *
+	 * Note:
+	 * CLKH is not allowed to be 0, in this case I2C clock is not generated
+	 * at all
 	 */
-	if (clk >= clkl + d) {
+	if (clk > clkl + d) {
 		clkh = clk - clkl - d;
 		clkl -= d;
 	} else {
-		clkh = 0;
+		clkh = 1;
 		clkl = clk - (d << 1);
 	}