linux-kernel - [PATCH] i2c: mediatek: Get device clock-stretch time via dts

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Message-ID: <1612348525-13364-1-git-send-email-qii.wang@mediatek.com>
Date:   Wed, 3 Feb 2021 18:35:25 +0800
From:   <qii.wang@...iatek.com>
To:     <wsa@...-dreams.de>
CC:     <matthias.bgg@...il.com>, <linux-i2c@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>,
        <srv_heupstream@...iatek.com>, <leilk.liu@...iatek.com>,
        <qii.wang@...iatek.com>
Subject: [PATCH] i2c: mediatek: Get device clock-stretch time via dts

From: Qii Wang <qii.wang@...iatek.com>

tSU,STA/tHD,STA/tSU,STOP maybe out of spec due to device
clock-stretching or circuit loss, we could get device
clock-stretch time from dts to adjust these parameters
to meet the spec via EXT_CONF register.

Signed-off-by: Qii Wang <qii.wang@...iatek.com>
---
 drivers/i2c/busses/i2c-mt65xx.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
index 2ffd2f3..47c7255 100644
--- a/drivers/i2c/busses/i2c-mt65xx.c
+++ b/drivers/i2c/busses/i2c-mt65xx.c
@@ -245,6 +245,7 @@ struct mtk_i2c {
 	u16 irq_stat;			/* interrupt status */
 	unsigned int clk_src_div;
 	unsigned int speed_hz;		/* The speed in transfer */
+	unsigned int clock_stretch_ns;
 	enum mtk_trans_op op;
 	u16 timing_reg;
 	u16 high_speed_reg;
@@ -607,7 +608,8 @@ static int mtk_i2c_check_ac_timing(struct mtk_i2c *i2c,
 	else
 		clk_ns = sample_ns / 2;
 
-	su_sta_cnt = DIV_ROUND_UP(spec->min_su_sta_ns, clk_ns);
+	su_sta_cnt = DIV_ROUND_UP(spec->min_su_sta_ns + i2c->clock_stretch_ns,
+				  clk_ns);
 	if (su_sta_cnt > max_sta_cnt)
 		return -1;
 
@@ -1171,6 +1173,8 @@ static int mtk_i2c_parse_dt(struct device_node *np, struct mtk_i2c *i2c)
 	if (i2c->clk_src_div == 0)
 		return -EINVAL;
 
+	of_property_read_u32(np, "clock-stretch-ns", &i2c->clock_stretch_ns);
+
 	i2c->have_pmic = of_property_read_bool(np, "mediatek,have-pmic");
 	i2c->use_push_pull =
 		of_property_read_bool(np, "mediatek,use-push-pull");
-- 
1.9.1