linux-kernel - Re: [PATCH v2 2/2] i2c: qup: support SMBus block read

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Message-ID: <757c18e2-562a-9f43-0fb6-ab3e7ac3af88@codeaurora.org>
Date:	Thu, 19 May 2016 14:14:02 -0600
From:	Naveen Kaje <nkaje@...eaurora.org>
To:	Sricharan <sricharan@...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, austinwc@...eaurora.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 2/2] i2c: qup: support SMBus block read

Hi Sricharan,


On 5/18/2016 1:06 AM, Sricharan wrote:
> Hi,
>
> <snip..>
>
>> +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;
>> +	int data_len = qup_i2c_get_data_len(qup);
>> +
>> +	if (msg->len > 1) {
>> +		tags[len++] = QUP_TAG_V2_DATARD_STOP;
>> +		tags[len++] = data_len - 1;
>> +	} else {
>      So we hit this else part for msg->len = 1 and this case blk.pos = 0
>      will always be true right ?
Yes, will fix that in V3.
>
>> +		if (qup->blk.pos == 0) {
>> +			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;
>> +		/* 0 implies 256 bytes */
>> +		if (data_len == QUP_READ_LIMIT)
>> +			tags[len++] = 0;
>> +		else
>> +			tags[len++] = data_len;
>> +	}
>         Even data_len will always be '1' right ?
Yes, but here preferably we use a variable than a number without a context.
>> +	return len;
>> +}
>> +
>>   static int qup_i2c_set_tags(u8 *tags, struct qup_i2c_dev *qup,
>>   			    struct i2c_msg *msg,  int is_dma)  { @@ -526,6
>> +559,10 @@ 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 +1102,17 @@ 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 +1132,8 @@ 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;
> 	A space around '+' ?
Thanks, will fix that.
>
>> +			qup->pos++;
>>   		}
>>   	}
>>
>> @@ -1128,6 +1173,22 @@ 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);
>> +			qup_i2c_issue_xfer_v2(qup, msg);
>> +			ret = qup_i2c_wait_for_complete(qup, msg);
>> +			if (ret)
>> +				goto err;
> 		Is the issue_xfer_v2 needed inside this here ?
No, qup_i2c_issue_xfer_v2 is needed so that we read rest of the data 
that is indicated by the length we read earlier.
>
>> +			qup_i2c_set_blk_data(qup, msg);
>> +		}
>>   	} while (qup->blk.pos < qup->blk.count);
>     Regards,
>       Sricharan

Thanks,
Naveen
>