linux-kernel - [PATCH v4] i2c: i2c-qcom-geni: Correct I2C TRE sequence

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Message-Id: <20240212125239.7764-1-quic_vdadhani@quicinc.com>
Date: Mon, 12 Feb 2024 18:22:39 +0530
From: Viken Dadhaniya <quic_vdadhani@...cinc.com>
To: andersson@...nel.org, konrad.dybcio@...aro.org, andi.shyti@...nel.org,
        linux-arm-msm@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org, vkoul@...nel.org,
        quic_bjorande@...cinc.com, manivannan.sadhasivam@...aro.org,
        bryan.odonoghue@...aro.org, dmitry.baryshkov@...aro.org
Cc: quic_msavaliy@...cinc.com, quic_vtanuku@...cinc.com,
        Viken Dadhaniya <quic_vdadhani@...cinc.com>
Subject: [PATCH v4] i2c: i2c-qcom-geni: Correct I2C TRE sequence

For i2c read operation in GSI mode, we are getting timeout
due to malformed TRE basically incorrect TRE sequence
in gpi(drivers/dma/qcom/gpi.c) driver.

I2C driver has geni_i2c_gpi(I2C_WRITE) function which generates GO TRE and
geni_i2c_gpi(I2C_READ)generates DMA TRE. Hence to generate GO TRE before
DMA TRE, we should move geni_i2c_gpi(I2C_WRITE) before
geni_i2c_gpi(I2C_READ) inside the I2C GSI mode transfer function
i.e. geni_i2c_gpi_xfer().

TRE stands for Transfer Ring Element - which is basically an element with
size of 4 words. It contains all information like slave address,
clk divider, dma address value data size etc).

Mainly we have 3 TREs(Config, GO and DMA tre).
- CONFIG TRE : consists of internal register configuration which is
               required before start of the transfer.
- DMA TRE :    contains DDR/Memory address, called as DMA descriptor.
- GO TRE :     contains Transfer directions, slave ID, Delay flags, Length
               of the transfer.

I2c driver calls GPI driver API to config each TRE depending on the
protocol.

For read operation tre sequence will be as below which is not aligned
to hardware programming guide.

- CONFIG tre
- DMA tre
- GO tre

As per Qualcomm's internal Hardware Programming Guide, we should configure
TREs in below sequence for any RX only transfer.

- CONFIG tre
- GO tre
- DMA tre

Fixes: d8703554f4de ("i2c: qcom-geni: Add support for GPI DMA")
Reviewed-by: Andi Shyti <andi.shyti@...nel.org>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Tested-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org> # qrb5165-rb5
Co-developed-by: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
Signed-off-by: Viken Dadhaniya <quic_vdadhani@...cinc.com>

---
v3 -> v4:
- Update commit log.
- Add review/tested/co-develop tag.
- Fix patch title by adding "PATCH" string.

v2 -> v3:
- Update commit log to explain change in simple way.
- Correct fix tag format.

v1 -> v2:
- Remove redundant check.
- update commit log.
- add fix tag.
---
---
 drivers/i2c/busses/i2c-qcom-geni.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
index 0d2e7171e3a6..da94df466e83 100644
--- a/drivers/i2c/busses/i2c-qcom-geni.c
+++ b/drivers/i2c/busses/i2c-qcom-geni.c
@@ -613,20 +613,20 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
 
 		peripheral.addr = msgs[i].addr;
 
+		ret =  geni_i2c_gpi(gi2c, &msgs[i], &config,
+				    &tx_addr, &tx_buf, I2C_WRITE, gi2c->tx_c);
+		if (ret)
+			goto err;
+
 		if (msgs[i].flags & I2C_M_RD) {
 			ret =  geni_i2c_gpi(gi2c, &msgs[i], &config,
 					    &rx_addr, &rx_buf, I2C_READ, gi2c->rx_c);
 			if (ret)
 				goto err;
-		}
-
-		ret =  geni_i2c_gpi(gi2c, &msgs[i], &config,
-				    &tx_addr, &tx_buf, I2C_WRITE, gi2c->tx_c);
-		if (ret)
-			goto err;
 
-		if (msgs[i].flags & I2C_M_RD)
 			dma_async_issue_pending(gi2c->rx_c);
+		}
+
 		dma_async_issue_pending(gi2c->tx_c);
 
 		timeout = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
-- 
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