linux-kernel - [PATCH 3/3] i2c: mediatek: Use scl_int_delay

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Date:   Sat, 17 Apr 2021 14:46:52 +0800
From:   Qii Wang <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 3/3] i2c: mediatek: Use scl_int_delay_ns to compensate clock-stretching

The parameters of tSU,STA/tHD,STA/tSU,STOP maybe out of spec due
to device clock-stretch or circuit loss, we could get a suitable
scl_int_delay_ns from i2c_timings to compensate 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 bf25acb..5ddfa4e 100644
--- a/drivers/i2c/busses/i2c-mt65xx.c
+++ b/drivers/i2c/busses/i2c-mt65xx.c
@@ -231,6 +231,7 @@ struct mtk_i2c {
 	struct i2c_adapter adap;	/* i2c host adapter */
 	struct device *dev;
 	struct completion msg_complete;
+	struct i2c_timings timing_info;
 
 	/* set in i2c probe */
 	void __iomem *base;		/* i2c base addr */
@@ -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->timing_info.scl_int_delay_ns, clk_ns);
 	if (su_sta_cnt > max_sta_cnt)
 		return -1;
 
@@ -1176,6 +1178,8 @@ static int mtk_i2c_parse_dt(struct device_node *np, struct mtk_i2c *i2c)
 	i2c->use_push_pull =
 		of_property_read_bool(np, "mediatek,use-push-pull");
 
+	i2c_parse_fw_timings(i2c->dev, &i2c->timing_info, true);
+
 	return 0;
 }
 
-- 
1.9.1