| Message ID | 1453197766-18976-4-git-send-email-sricharan@codeaurora.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
Hi, > "If this is the last message in a group, it is followed by a STOP. > Otherwise it is followed by the next @i2c_msg transaction segment, > beginning with a (repeated) START" This is correct. > So the expectation is that there is no 'STOP' bit inbetween individual > i2c_msg segments with repeated 'START'. The QUP i2c hardware has no way > to inform that there should not be a 'STOP' at the end of transaction. > The only way to implement this is to coalesce all the i2c_msg in i2c_msgs > in to one transaction and transfer them. Adding the support for the same. So, there will not be a REP_START condition on the bus? I am sorry to say that I can't accept this. A REP_START is a REP_START and nothing else. There are devices which will get confused if there is no real REP_START condition. Without knowing the HW in detail, can't you implement I2C_M_NOSTART and let the touchscreen driver use it via regmap? That would be the proper way (from what I understand). Regards, Wolfram
Hi Wolfram, > -----Original Message----- > From: Wolfram Sang [mailto:wsa@the-dreams.de] > Sent: Sunday, January 24, 2016 4:59 PM > To: Sricharan R > Cc: devicetree@vger.kernel.org; linux-arm-msm@vger.kernel.org; > agross@codeaurora.org; linux-kernel@vger.kernel.org; linux- > i2c@vger.kernel.org; iivanov@mm-sol.com; galak@codeaurora.org; > dmaengine@vger.kernel.org; linux-arm-kernel@lists.infradead.org; > andy.gross@linaro.org; ntelkar@codeaurora.org; architt@codeaurora.org > Subject: Re: [PATCH V7 3/6] i2c: qup: Transfer each i2c_msg in i2c_msgs > without a stop bit > > Hi, > > > "If this is the last message in a group, it is followed by a STOP. > > Otherwise it is followed by the next @i2c_msg transaction segment, > > beginning with a (repeated) START" > > This is correct. > > > So the expectation is that there is no 'STOP' bit inbetween individual > > i2c_msg segments with repeated 'START'. The QUP i2c hardware has no > > way to inform that there should not be a 'STOP' at the end of transaction. > > The only way to implement this is to coalesce all the i2c_msg in > > i2c_msgs in to one transaction and transfer them. Adding the support for > the same. > > So, there will not be a REP_START condition on the bus? I am sorry to say that > I can't accept this. A REP_START is a REP_START and nothing else. There are > devices which will get confused if there is no real REP_START condition. > > Without knowing the HW in detail, can't you implement I2C_M_NOSTART > and let the touchscreen driver use it via regmap? That would be the proper > way (from what I understand). Ah, so what I meant above is there is no 'STOP' bit between each msg in i2c_msgs, but 'REAPEATED_START' still holds true. We are sending 'START' bit for each msg. So these is how each msg in i2c_msg is sent, |------MSG1--------|-----MSG2---------|------MSG3------------| |START|DATA|------|START|DATA|---|START|DATA|STOP| If my commit text does not make this clear, I can reword that ? Regards, Sricharan -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi, > Ah, so what I meant above is there is no 'STOP' bit between each msg in > i2c_msgs, > but 'REAPEATED_START' still holds true. We are sending 'START' bit for each > msg. > So these is how each msg in i2c_msg is sent, > > |------MSG1--------|-----MSG2---------|------MSG3------------| > > |START|DATA|------|START|DATA|---|START|DATA|STOP| > > If my commit text does not make this clear, I can reword that ? OK, now this looks to me perfectly fine: A number of *messages* concatenated into one *transfer* by repeated start. That's the way it should be. So, I'd simply remove these words: "The QUP i2c hardware has no way to inform that there should not be a 'STOP' at the end of transaction. The only way to implement this is to coalesce all the i2c_msg in i2c_msgs in to one transaction and transfer them." This sounded like the HW needed a special handling, so I was under the impression REP_START was broken. However, unless I misunderstood something again, this now sounds like the standard case and we can keep the commit message simple. If you are okay with that, I can update it here, no need to resend. Thanks, Wolfram
Hi Wolfram, > -----Original Message----- > From: linux-arm-kernel [mailto:linux-arm-kernel- > bounces@lists.infradead.org] On Behalf Of Wolfram Sang > Sent: Friday, February 05, 2016 1:39 AM > To: Sricharan > Cc: devicetree@vger.kernel.org; architt@codeaurora.org; linux-arm- > msm@vger.kernel.org; ntelkar@codeaurora.org; galak@codeaurora.org; > linux-kernel@vger.kernel.org; andy.gross@linaro.org; linux- > i2c@vger.kernel.org; iivanov@mm-sol.com; agross@codeaurora.org; > dmaengine@vger.kernel.org; linux-arm-kernel@lists.infradead.org > Subject: Re: [PATCH V7 3/6] i2c: qup: Transfer each i2c_msg in i2c_msgs > without a stop bit > > Hi, > > > Ah, so what I meant above is there is no 'STOP' bit between each msg > > in i2c_msgs, but 'REAPEATED_START' still holds true. We are sending > > 'START' bit for each msg. > > So these is how each msg in i2c_msg is sent, > > > > |------MSG1--------|-----MSG2---------|------MSG3------------| > > > > |START|DATA|------|START|DATA|---|START|DATA|STOP| > > > > If my commit text does not make this clear, I can reword that ? > > OK, now this looks to me perfectly fine: A number of *messages* > concatenated into one *transfer* by repeated start. That's the way it should > be. > > So, I'd simply remove these words: > > "The QUP i2c hardware has no way to inform that there should not be a > 'STOP' at the end of transaction. The only way to implement this is to > coalesce all the i2c_msg in i2c_msgs in to one transaction and transfer them." > > This sounded like the HW needed a special handling, so I was under the > impression REP_START was broken. However, unless I misunderstood > something again, this now sounds like the standard case and we can keep > the commit message simple. If you are okay with that, I can update it here, > no need to resend. > Yes the above modified commit text looks perfect to be updated and thanks for the update as well. Regards, Sricharan -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Jan 19, 2016 at 03:32:43PM +0530, Sricharan R wrote: > The definition of i2c_msg says that > > "If this is the last message in a group, it is followed by a STOP. > Otherwise it is followed by the next @i2c_msg transaction segment, > beginning with a (repeated) START" > > So the expectation is that there is no 'STOP' bit inbetween individual > i2c_msg segments with repeated 'START'. The QUP i2c hardware has no way > to inform that there should not be a 'STOP' at the end of transaction. > The only way to implement this is to coalesce all the i2c_msg in i2c_msgs > in to one transaction and transfer them. Adding the support for the same. > > This is required for some clients like touchscreen which keeps > incrementing counts across individual transfers and 'STOP' bit inbetween > resets the counter, which is not required. > > This patch adds the support in non-dma mode. > > Signed-off-by: Sricharan R <sricharan@codeaurora.org> > Reviewed-by: Andy Gross <andy.gross@linaro.org> > Tested-by: Archit Taneja <architt@codeaurora.org> > Tested-by: Telkar Nagender <ntelkar@codeaurora.org> Shortened the commit message and applied to for-next, thanks!
diff --git a/drivers/i2c/busses/i2c-qup.c b/drivers/i2c/busses/i2c-qup.c index 715d4d7..f9009d6 100644 --- a/drivers/i2c/busses/i2c-qup.c +++ b/drivers/i2c/busses/i2c-qup.c @@ -112,6 +112,7 @@ #define SET_BIT 0x1 #define RESET_BIT 0x0 #define ONE_BYTE 0x1 +#define QUP_I2C_MX_CONFIG_DURING_RUN BIT(31) struct qup_i2c_block { int count; @@ -147,6 +148,12 @@ struct qup_i2c_dev { /* QUP core errors */ u32 qup_err; + /* To check if this is the last msg */ + bool is_last; + + /* To configure when bus is in run state */ + int config_run; + struct completion xfer; }; @@ -269,7 +276,7 @@ static int qup_i2c_wait_ready(struct qup_i2c_dev *qup, int op, bool val, status = readl(qup->base + QUP_I2C_STATUS); if (((opflags & op) >> shift) == val) { - if (op == QUP_OUT_NOT_EMPTY) { + if ((op == QUP_OUT_NOT_EMPTY) && qup->is_last) { if (!(status & I2C_STATUS_BUS_ACTIVE)) return 0; } else { @@ -290,6 +297,8 @@ static void qup_i2c_set_write_mode_v2(struct qup_i2c_dev *qup, /* Number of entries to shift out, including the tags */ int total = msg->len + qup->blk.tx_tag_len; + total |= qup->config_run; + if (total < qup->out_fifo_sz) { /* FIFO mode */ writel(QUP_REPACK_EN, qup->base + QUP_IO_MODE); @@ -443,7 +452,7 @@ static int qup_i2c_set_tags(u8 *tags, struct qup_i2c_dev *qup, } /* Send _STOP commands for the last block */ - if (qup->blk.pos == (qup->blk.count - 1)) { + if ((qup->blk.pos == (qup->blk.count - 1)) && qup->is_last) { if (msg->flags & I2C_M_RD) tags[len++] = QUP_TAG_V2_DATARD_STOP; else @@ -581,7 +590,6 @@ static int qup_i2c_write_one(struct qup_i2c_dev *qup, struct i2c_msg *msg) /* Wait for the outstanding data in the fifo to drain */ ret = qup_i2c_wait_ready(qup, QUP_OUT_NOT_EMPTY, RESET_BIT, ONE_BYTE); - err: disable_irq(qup->irq); qup->msg = NULL; @@ -608,18 +616,20 @@ static void qup_i2c_set_read_mode_v2(struct qup_i2c_dev *qup, int len) int tx_len = qup->blk.tx_tag_len; len += qup->blk.rx_tag_len; + len |= qup->config_run; + tx_len |= qup->config_run; if (len < qup->in_fifo_sz) { /* FIFO mode */ writel(QUP_REPACK_EN, qup->base + QUP_IO_MODE); - writel(len, qup->base + QUP_MX_READ_CNT); writel(tx_len, qup->base + QUP_MX_WRITE_CNT); + writel(len, qup->base + QUP_MX_READ_CNT); } else { /* BLOCK mode (transfer data on chunks) */ writel(QUP_INPUT_BLK_MODE | QUP_REPACK_EN, qup->base + QUP_IO_MODE); - writel(len, qup->base + QUP_MX_INPUT_CNT); writel(tx_len, qup->base + QUP_MX_OUTPUT_CNT); + writel(len, qup->base + QUP_MX_INPUT_CNT); } } @@ -866,6 +876,12 @@ static int qup_i2c_xfer_v2(struct i2c_adapter *adap, goto out; } + qup->is_last = (idx == (num - 1)); + if (idx) + qup->config_run = QUP_I2C_MX_CONFIG_DURING_RUN; + else + qup->config_run = 0; + reinit_completion(&qup->xfer); if (msgs[idx].flags & I2C_M_RD) @@ -873,13 +889,13 @@ static int qup_i2c_xfer_v2(struct i2c_adapter *adap, else ret = qup_i2c_write_one_v2(qup, &msgs[idx]); - if (!ret) - ret = qup_i2c_change_state(qup, QUP_RESET_STATE); - if (ret) break; } + if (!ret) + ret = qup_i2c_change_state(qup, QUP_RESET_STATE); + if (ret == 0) ret = num; out: @@ -1057,6 +1073,8 @@ static int qup_i2c_probe(struct platform_device *pdev) i2c_set_adapdata(&qup->adap, qup); qup->adap.dev.parent = qup->dev; qup->adap.dev.of_node = pdev->dev.of_node; + qup->is_last = 1; + strlcpy(qup->adap.name, "QUP I2C adapter", sizeof(qup->adap.name)); pm_runtime_set_autosuspend_delay(qup->dev, MSEC_PER_SEC);