linux-kernel - RE: [PATCH v3 2/2] i2c: qup: support SMBus block read

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Message-ID: <000201d1b65e$256a7590$703f60b0$@codeaurora.org>
Date:	Wed, 25 May 2016 13:49:14 +0530
From:	"Sricharan" <sricharan@...eaurora.org>
To:	"'Austin Christ'" <austinwc@...eaurora.org>,
	<nkaje@...eaurora.org>, <wsa@...-dreams.de>,
	<linux-i2c@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Cc:	<linux-arm-msm@...r.kernel.org>, <rruigrok@...eaurora.org>,
	<timur@...eaurora.org>, <cov@...eaurora.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH v3 2/2] i2c: qup: support SMBus block read

Hi,

>From: Naveen Kaje <nkaje@...eaurora.org>
>
>I2C QUP driver relies on SMBus emulation support from the framework.
>To handle SMBus block reads, the driver should check I2C_M_RECV_LEN
>flag and should read the first byte received as the message length.
>
>The driver configures the QUP hardware to read one byte. Once the
>message length is known from this byte, the QUP hardware is configured
>to read the rest.
>
>Signed-off-by: Naveen Kaje <nkaje@...eaurora.org>
>Signed-off-by: Austin Christ <austinwc@...eaurora.org>
>---
> drivers/i2c/busses/i2c-qup.c | 68 ++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 65 insertions(+), 3 deletions(-)
>
>Changes:
>- v3:
> - clean up redundant checks
> - use constant instead of variable for smbus length field
>- v2:
> - rework the smbus block read and break into separate function
>
>diff --git a/drivers/i2c/busses/i2c-qup.c b/drivers/i2c/busses/i2c-qup.c
>index ea6ca5f..9fbed83 100644
>--- a/drivers/i2c/busses/i2c-qup.c
>+++ b/drivers/i2c/busses/i2c-qup.c
>@@ -517,6 +517,33 @@ static int qup_i2c_get_data_len(struct qup_i2c_dev *qup)
> 	return data_len;
> }
>
>+static bool qup_i2c_check_msg_len(struct i2c_msg *msg)
>+{
>+	return ((msg->flags & I2C_M_RD) && (msg->flags & I2C_M_RECV_LEN));
>+}
>+
>+static int qup_i2c_set_tags_smb(u16 addr, u8 *tags, struct qup_i2c_dev *qup,
>+			struct i2c_msg *msg)
>+{
>+	int len = 0;
>+
>+	if (msg->len > 1) {
>+		tags[len++] = QUP_TAG_V2_DATARD_STOP;
>+		tags[len++] = qup_i2c_get_data_len(qup) - 1;
>+	} else {
>+		tags[len++] = QUP_TAG_V2_START;
>+		tags[len++] = addr & 0xff;
>+
>+		if (msg->flags & I2C_M_TEN)
>+			tags[len++] = addr >> 8;
>+
>+		tags[len++] = QUP_TAG_V2_DATARD;
>+		/* Read 1 byte indicating the length of the SMBus message */
>+		tags[len++] = 1;
>+	}
>+	return len;
>+}
>+
> static int qup_i2c_set_tags(u8 *tags, struct qup_i2c_dev *qup,
> 			    struct i2c_msg *msg,  int is_dma)
> {
>@@ -526,6 +553,10 @@ static int qup_i2c_set_tags(u8 *tags, struct qup_i2c_dev *qup,
>
> 	int last = (qup->blk.pos == (qup->blk.count - 1)) && (qup->is_last);
>
>+	/* Handle tags for SMBus block read */
>+	if (qup_i2c_check_msg_len(msg))
>+		return qup_i2c_set_tags_smb(addr, tags, qup, msg);
>+
> 	if (qup->blk.pos == 0) {
> 		tags[len++] = QUP_TAG_V2_START;
> 		tags[len++] = addr & 0xff;
>@@ -1065,9 +1096,17 @@ static int qup_i2c_read_fifo_v2(struct qup_i2c_dev *qup,
> 				struct i2c_msg *msg)
> {
> 	u32 val;
>-	int idx, pos = 0, ret = 0, total;
>+	int idx, pos = 0, ret = 0, total, msg_offset = 0;
>
>+	/*
>+	 * If the message length is already read in
>+	 * the first byte of the buffer, account for
>+	 * that by setting the offset
>+	 */
>+	if (qup_i2c_check_msg_len(msg) && (msg->len > 1))
>+		msg_offset = 1;
> 	total = qup_i2c_get_data_len(qup);
>+	total -= msg_offset;
>
> 	/* 2 extra bytes for read tags */
> 	while (pos < (total + 2)) {
>@@ -1087,8 +1126,8 @@ static int qup_i2c_read_fifo_v2(struct qup_i2c_dev *qup,
>
> 			if (pos >= (total + 2))
> 				goto out;
>-
>-			msg->buf[qup->pos++] = val & 0xff;
>+			msg->buf[qup->pos + msg_offset] = val & 0xff;
>+			qup->pos++;
> 		}
> 	}
>
>@@ -1128,6 +1167,24 @@ static int qup_i2c_read_one_v2(struct qup_i2c_dev *qup, struct i2c_msg *msg)
> 			goto err;
>
> 		qup->blk.pos++;
>+
>+		/* Handle SMBus block read length */
>+		if (qup_i2c_check_msg_len(msg) && (msg->len == 1)) {
>+			if (msg->buf[0] > I2C_SMBUS_BLOCK_MAX) {
>+				ret = -EPROTO;
>+				goto err;
>+			}
>+			msg->len += msg->buf[0];
>+			qup->pos = 0;
>+			qup_i2c_set_read_mode_v2(qup, msg->len);
>+			ret = qup_i2c_issue_xfer_v2(qup, msg);
>+			if (ret)
>+				goto err;
>+			ret = qup_i2c_wait_for_complete(qup, msg);
>+			if (ret)
>+				goto err;
>+			qup_i2c_set_blk_data(qup, msg);
>+		}
> 	} while (qup->blk.pos < qup->blk.count);
>
> err:
>@@ -1210,6 +1267,11 @@ static int qup_i2c_xfer(struct i2c_adapter *adap,
> 			goto out;
> 		}
>
>+		if (qup_i2c_check_msg_len(&msgs[idx])) {
>+			ret = -EOPNOTSUPP;
>+			goto out;
>+		}
>+
> 		if (msgs[idx].flags & I2C_M_RD)
> 			ret = qup_i2c_read_one(qup, &msgs[idx]);
> 		else

Reviewed-by: sricharan@...eaurora.org

Regards,
 Sricharan