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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Alexandru M Stan <amstan@chromium.org>,
        Hsin-Yi Wang <hsinyi@chromium.org>,
        Qii Wang <qii.wang@mediatek.com>,
        Wolfram Sang <wsa@the-dreams.de>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.2 091/124] i2c: mediatek: disable zero-length transfers for mt8183
Date:   Fri, 20 Sep 2019 00:02:59 +0200
Message-Id: <20190919214822.352597931@linuxfoundation.org>
In-Reply-To: <20190919214819.198419517@linuxfoundation.org>
References: <20190919214819.198419517@linuxfoundation.org>
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From: Hsin-Yi Wang <hsinyi@chromium.org>

[ Upstream commit abf4923e97c3abbbd1e59f0e13c7c214c93c6aaa ]

Quoting from mt8183 datasheet, the number of transfers to be
transferred in one transaction should be set to bigger than 1,
so we should forbid zero-length transfer and update functionality.

Reported-by: Alexandru M Stan <amstan@chromium.org>
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Reviewed-by: Qii Wang <qii.wang@mediatek.com>
[wsa: shortened commit message a little]
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/i2c/busses/i2c-mt65xx.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
index 252edb433fdfb..29eae1bf4f861 100644
--- a/drivers/i2c/busses/i2c-mt65xx.c
+++ b/drivers/i2c/busses/i2c-mt65xx.c
@@ -234,6 +234,10 @@ static const struct i2c_adapter_quirks mt7622_i2c_quirks = {
 	.max_num_msgs = 255,
 };
 
+static const struct i2c_adapter_quirks mt8183_i2c_quirks = {
+	.flags = I2C_AQ_NO_ZERO_LEN,
+};
+
 static const struct mtk_i2c_compatible mt2712_compat = {
 	.regs = mt_i2c_regs_v1,
 	.pmic_i2c = 0,
@@ -298,6 +302,7 @@ static const struct mtk_i2c_compatible mt8173_compat = {
 };
 
 static const struct mtk_i2c_compatible mt8183_compat = {
+	.quirks = &mt8183_i2c_quirks,
 	.regs = mt_i2c_regs_v2,
 	.pmic_i2c = 0,
 	.dcm = 0,
@@ -870,7 +875,11 @@ static irqreturn_t mtk_i2c_irq(int irqno, void *dev_id)
 
 static u32 mtk_i2c_functionality(struct i2c_adapter *adap)
 {
-	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+	if (adap->quirks->flags & I2C_AQ_NO_ZERO_LEN)
+		return I2C_FUNC_I2C |
+			(I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK);
+	else
+		return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 }
 
 static const struct i2c_algorithm mtk_i2c_algorithm = {
-- 
2.20.1