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From:   Rayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>
To:     Wolfram Sang <wsa@kernel.org>, linux-i2c@vger.kernel.org,
        linux-kernel@vger.kernel.org, Ray Jui <rjui@broadcom.com>,
        Scott Branden <sbranden@broadcom.com>,
        bcm-kernel-feedback-list@broadcom.com,
        Lori Hikichi <lori.hikichi@broadcom.com>,
        Robert Richter <rrichter@marvell.com>,
        Nishka Dasgupta <nishkadg.linux@gmail.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        linux-arm-kernel@lists.infradead.org
Cc:     Rayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>
Subject: [PATCH v2 2/2] i2c: iproc: add slave pec support
Date:   Fri, 17 Jul 2020 14:31:55 +0530
Message-Id: <20200717090155.10383-3-rayagonda.kokatanur@broadcom.com>
In-Reply-To: <20200717090155.10383-1-rayagonda.kokatanur@broadcom.com>
References: <20200717090155.10383-1-rayagonda.kokatanur@broadcom.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Iproc supports PEC computation and checking in both Master
and Slave mode.

This patch adds support for PEC in slave mode.

As per hw spec, PEC ERROR status bits are [29:28] in S_RX_OFFSET
register, hence this patch corrects the S_RX_PEC_ERR_SHIFT.

Signed-off-by: Rayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>
---
Changes from v1:
 -Address review comments from Andy Shevchenko
  Update commit message,
  Rewrite bcm_iproc_smbus_check_slave_pec() to remove local
  variable ret and type casting,
  Use positive condition.

 drivers/i2c/busses/i2c-bcm-iproc.c | 49 +++++++++++++++++++++++++++---
 1 file changed, 45 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-bcm-iproc.c b/drivers/i2c/busses/i2c-bcm-iproc.c
index 8a3c98866fb7..cfa7b044209e 100644
--- a/drivers/i2c/busses/i2c-bcm-iproc.c
+++ b/drivers/i2c/busses/i2c-bcm-iproc.c
@@ -93,6 +93,7 @@
 #define S_CMD_STATUS_MASK            0x07
 #define S_CMD_STATUS_SUCCESS         0x0
 #define S_CMD_STATUS_TIMEOUT         0x5
+#define S_CMD_PEC_SHIFT              8
 
 #define IE_OFFSET                    0x38
 #define IE_M_RX_FIFO_FULL_SHIFT      31
@@ -138,7 +139,9 @@
 #define S_RX_OFFSET                  0x4c
 #define S_RX_STATUS_SHIFT            30
 #define S_RX_STATUS_MASK             0x03
-#define S_RX_PEC_ERR_SHIFT           29
+#define S_RX_PEC_ERR_SHIFT           28
+#define S_RX_PEC_ERR_MASK            0x3
+#define S_RX_PEC_ERR                 0x1
 #define S_RX_DATA_SHIFT              0
 #define S_RX_DATA_MASK               0xff
 
@@ -205,6 +208,8 @@ struct bcm_iproc_i2c_dev {
 	/* bytes that have been read */
 	unsigned int rx_bytes;
 	unsigned int thld_bytes;
+
+	bool en_s_pec;
 };
 
 /*
@@ -321,6 +326,23 @@ static void bcm_iproc_i2c_check_slave_status(
 	}
 }
 
+static int bcm_iproc_smbus_check_slave_pec(struct bcm_iproc_i2c_dev *iproc_i2c,
+					   u32 val)
+{
+	u8 err_status;
+
+	if (!iproc_i2c->en_s_pec)
+		return 0;
+
+	err_status = (val >> S_RX_PEC_ERR_SHIFT) & S_RX_PEC_ERR_MASK;
+	if (err_status == S_RX_PEC_ERR) {
+		dev_err(iproc_i2c->device, "Slave PEC error\n");
+		return -EBADMSG;
+	}
+
+	return 0;
+}
+
 static bool bcm_iproc_i2c_slave_isr(struct bcm_iproc_i2c_dev *iproc_i2c,
 				    u32 status)
 {
@@ -347,6 +369,8 @@ static bool bcm_iproc_i2c_slave_isr(struct bcm_iproc_i2c_dev *iproc_i2c,
 			iproc_i2c_wr_reg(iproc_i2c, S_TX_OFFSET, value);
 
 			val = BIT(S_CMD_START_BUSY_SHIFT);
+			if (iproc_i2c->en_s_pec)
+				val |= BIT(S_CMD_PEC_SHIFT);
 			iproc_i2c_wr_reg(iproc_i2c, S_CMD_OFFSET, val);
 
 			/*
@@ -361,9 +385,19 @@ static bool bcm_iproc_i2c_slave_isr(struct bcm_iproc_i2c_dev *iproc_i2c,
 			value = (u8)((val >> S_RX_DATA_SHIFT) & S_RX_DATA_MASK);
 			i2c_slave_event(iproc_i2c->slave,
 					I2C_SLAVE_WRITE_RECEIVED, &value);
-			if (rx_status == I2C_SLAVE_RX_END)
-				i2c_slave_event(iproc_i2c->slave,
-						I2C_SLAVE_STOP, &value);
+			if (rx_status == I2C_SLAVE_RX_END) {
+				int ret;
+
+				ret = bcm_iproc_smbus_check_slave_pec(iproc_i2c,
+								      val);
+				if (ret)
+					i2c_slave_event(iproc_i2c->slave,
+							I2C_SLAVE_PEC_ERR,
+							&value);
+				else
+					i2c_slave_event(iproc_i2c->slave,
+							I2C_SLAVE_STOP, &value);
+			}
 		}
 	} else if (status & BIT(IS_S_TX_UNDERRUN_SHIFT)) {
 		/* Master read other than start */
@@ -372,6 +406,8 @@ static bool bcm_iproc_i2c_slave_isr(struct bcm_iproc_i2c_dev *iproc_i2c,
 
 		iproc_i2c_wr_reg(iproc_i2c, S_TX_OFFSET, value);
 		val = BIT(S_CMD_START_BUSY_SHIFT);
+		if (iproc_i2c->en_s_pec)
+			val |= BIT(S_CMD_PEC_SHIFT);
 		iproc_i2c_wr_reg(iproc_i2c, S_CMD_OFFSET, val);
 	}
 
@@ -1065,6 +1101,11 @@ static int bcm_iproc_i2c_reg_slave(struct i2c_client *slave)
 	if (slave->flags & I2C_CLIENT_TEN)
 		return -EAFNOSUPPORT;
 
+	/* Enable partial slave HW PEC support if requested by the client */
+	iproc_i2c->en_s_pec = !!(slave->flags & I2C_CLIENT_PEC);
+	if (iproc_i2c->en_s_pec)
+		dev_info(iproc_i2c->device, "Enable PEC\n");
+
 	iproc_i2c->slave = slave;
 	bcm_iproc_i2c_slave_init(iproc_i2c, false);
 	return 0;
-- 
2.17.1