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Message-ID: <20241218-football-composure-e56df2461461@spud>
Date: Wed, 18 Dec 2024 12:07:40 +0000
From: Conor Dooley <conor@...nel.org>
To: linux-i2c@...r.kernel.org
Cc: conor@...nel.org,
Conor Dooley <conor.dooley@...rochip.com>,
Daire McNamara <daire.mcnamara@...rochip.com>,
Andi Shyti <andi.shyti@...nel.org>,
Wolfram Sang <wsa@...nel.org>,
linux-riscv@...ts.infradead.org,
linux-kernel@...r.kernel.org,
stable@...r.kernel.org
Subject: [PATCH v2 1/2] i2c: microchip-core: actually use repeated sends
From: Conor Dooley <conor.dooley@...rochip.com>
At present, where repeated sends are intended to be used, the
i2c-microchip-core driver sends a stop followed by a start. Lots of i2c
devices must not malfunction in the face of this behaviour, because the
driver has operated like this for years! Try to keep track of whether or
not a repeated send is required, and suppress sending a stop in these
cases.
CC: stable@...r.kernel.org
Fixes: 64a6f1c4987e ("i2c: add support for microchip fpga i2c controllers")
Signed-off-by: Conor Dooley <conor.dooley@...rochip.com>
---
drivers/i2c/busses/i2c-microchip-corei2c.c | 124 ++++++++++++++++-----
1 file changed, 96 insertions(+), 28 deletions(-)
diff --git a/drivers/i2c/busses/i2c-microchip-corei2c.c b/drivers/i2c/busses/i2c-microchip-corei2c.c
index 0b0a1c4d17ca..e5af38dfaa81 100644
--- a/drivers/i2c/busses/i2c-microchip-corei2c.c
+++ b/drivers/i2c/busses/i2c-microchip-corei2c.c
@@ -93,27 +93,35 @@
* @base: pointer to register struct
* @dev: device reference
* @i2c_clk: clock reference for i2c input clock
+ * @msg_queue: pointer to the messages requiring sending
* @buf: pointer to msg buffer for easier use
* @msg_complete: xfer completion object
* @adapter: core i2c abstraction
* @msg_err: error code for completed message
* @bus_clk_rate: current i2c bus clock rate
* @isr_status: cached copy of local ISR status
+ * @total_num: total number of messages to be sent/received
+ * @current_num: index of the current message being sent/received
* @msg_len: number of bytes transferred in msg
* @addr: address of the current slave
+ * @restart_needed: whether or not a repeated start is required after current message
*/
struct mchp_corei2c_dev {
void __iomem *base;
struct device *dev;
struct clk *i2c_clk;
+ struct i2c_msg *msg_queue;
u8 *buf;
struct completion msg_complete;
struct i2c_adapter adapter;
int msg_err;
+ int total_num;
+ int current_num;
u32 bus_clk_rate;
u32 isr_status;
u16 msg_len;
u8 addr;
+ bool restart_needed;
};
static void mchp_corei2c_core_disable(struct mchp_corei2c_dev *idev)
@@ -222,6 +230,47 @@ static int mchp_corei2c_fill_tx(struct mchp_corei2c_dev *idev)
return 0;
}
+static void mchp_corei2c_next_msg(struct mchp_corei2c_dev *idev)
+{
+ struct i2c_msg *this_msg;
+ u8 ctrl;
+
+ if (idev->current_num >= idev->total_num) {
+ complete(&idev->msg_complete);
+ return;
+ }
+
+ /*
+ * If there's been an error, the isr needs to return control
+ * to the "main" part of the driver, so as not to keep sending
+ * messages once it completes and clears the SI bit.
+ */
+ if (idev->msg_err) {
+ complete(&idev->msg_complete);
+ return;
+ }
+
+ this_msg = idev->msg_queue++;
+
+ if (idev->current_num < (idev->total_num - 1)) {
+ struct i2c_msg *next_msg = idev->msg_queue;
+
+ idev->restart_needed = next_msg->flags & I2C_M_RD;
+ } else {
+ idev->restart_needed = false;
+ }
+
+ idev->addr = i2c_8bit_addr_from_msg(this_msg);
+ idev->msg_len = this_msg->len;
+ idev->buf = this_msg->buf;
+
+ ctrl = readb(idev->base + CORE_I2C_CTRL);
+ ctrl |= CTRL_STA;
+ writeb(ctrl, idev->base + CORE_I2C_CTRL);
+
+ idev->current_num++;
+}
+
static irqreturn_t mchp_corei2c_handle_isr(struct mchp_corei2c_dev *idev)
{
u32 status = idev->isr_status;
@@ -247,10 +296,14 @@ static irqreturn_t mchp_corei2c_handle_isr(struct mchp_corei2c_dev *idev)
break;
case STATUS_M_SLAW_ACK:
case STATUS_M_TX_DATA_ACK:
- if (idev->msg_len > 0)
+ if (idev->msg_len > 0) {
mchp_corei2c_fill_tx(idev);
- else
- last_byte = true;
+ } else {
+ if (idev->restart_needed)
+ finished = true;
+ else
+ last_byte = true;
+ }
break;
case STATUS_M_TX_DATA_NACK:
case STATUS_M_SLAR_NACK:
@@ -287,7 +340,7 @@ static irqreturn_t mchp_corei2c_handle_isr(struct mchp_corei2c_dev *idev)
mchp_corei2c_stop(idev);
if (last_byte || finished)
- complete(&idev->msg_complete);
+ mchp_corei2c_next_msg(idev);
return IRQ_HANDLED;
}
@@ -311,21 +364,48 @@ static irqreturn_t mchp_corei2c_isr(int irq, void *_dev)
return ret;
}
-static int mchp_corei2c_xfer_msg(struct mchp_corei2c_dev *idev,
- struct i2c_msg *msg)
+static int mchp_corei2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
+ int num)
{
- u8 ctrl;
+ struct mchp_corei2c_dev *idev = i2c_get_adapdata(adap);
+ struct i2c_msg *this_msg = msgs;
unsigned long time_left;
-
- idev->addr = i2c_8bit_addr_from_msg(msg);
- idev->msg_len = msg->len;
- idev->buf = msg->buf;
- idev->msg_err = 0;
-
- reinit_completion(&idev->msg_complete);
+ u8 ctrl;
mchp_corei2c_core_enable(idev);
+ /*
+ * The isr controls the flow of a transfer, this info needs to be saved
+ * to a location that it can access the queue information from.
+ */
+ idev->restart_needed = false;
+ idev->msg_queue = msgs;
+ idev->total_num = num;
+ idev->current_num = 0;
+
+ /*
+ * But the first entry to the isr is triggered by the start in this
+ * function, so the first message needs to be "dequeued".
+ */
+ idev->addr = i2c_8bit_addr_from_msg(this_msg);
+ idev->msg_len = this_msg->len;
+ idev->buf = this_msg->buf;
+ idev->msg_err = 0;
+
+ if (idev->total_num > 1) {
+ struct i2c_msg *next_msg = msgs + 1;
+
+ idev->restart_needed = next_msg->flags & I2C_M_RD;
+ }
+
+ idev->current_num++;
+ idev->msg_queue++;
+
+ reinit_completion(&idev->msg_complete);
+
+ /*
+ * Send the first start to pass control to the isr
+ */
ctrl = readb(idev->base + CORE_I2C_CTRL);
ctrl |= CTRL_STA;
writeb(ctrl, idev->base + CORE_I2C_CTRL);
@@ -335,20 +415,8 @@ static int mchp_corei2c_xfer_msg(struct mchp_corei2c_dev *idev,
if (!time_left)
return -ETIMEDOUT;
- return idev->msg_err;
-}
-
-static int mchp_corei2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
- int num)
-{
- struct mchp_corei2c_dev *idev = i2c_get_adapdata(adap);
- int i, ret;
-
- for (i = 0; i < num; i++) {
- ret = mchp_corei2c_xfer_msg(idev, msgs++);
- if (ret)
- return ret;
- }
+ if (idev->msg_err)
+ return idev->msg_err;
return num;
}
--
2.45.2
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