This is a note to let you know that I've just added the patch titled
i2c: designware: Disable TX_EMPTY irq while waiting for block length byte
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
i2c-designware-disable-tx_empty-irq-while-waiting-for-block-length-byte.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e8183fa10c25c7b3c20670bf2b430ddcc1ee03c0 Mon Sep 17 00:00:00 2001
From: Tam Nguyen <tamnguyenchi@xxxxxxxxxxxxxxxxxxxxxx>
Date: Thu, 2 Nov 2023 10:30:08 +0700
Subject: i2c: designware: Disable TX_EMPTY irq while waiting for block length byte
From: Tam Nguyen <tamnguyenchi@xxxxxxxxxxxxxxxxxxxxxx>
commit e8183fa10c25c7b3c20670bf2b430ddcc1ee03c0 upstream.
During SMBus block data read process, we have seen high interrupt rate
because of TX_EMPTY irq status while waiting for block length byte (the
first data byte after the address phase). The interrupt handler does not
do anything because the internal state is kept as STATUS_WRITE_IN_PROGRESS.
Hence, we should disable TX_EMPTY IRQ until I2C DesignWare receives
first data byte from I2C device, then re-enable it to resume SMBus
transaction.
It takes 0.789 ms for host to receive data length from slave.
Without the patch, i2c_dw_isr() is called 99 times by TX_EMPTY interrupt.
And it is none after applying the patch.
Cc: stable@xxxxxxxxxxxxxxx
Co-developed-by: Chuong Tran <chuong@xxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Chuong Tran <chuong@xxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Tam Nguyen <tamnguyenchi@xxxxxxxxxxxxxxxxxxxxxx>
Acked-by: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>
Reviewed-by: Serge Semin <fancer.lancer@xxxxxxxxx>
Signed-off-by: Wolfram Sang <wsa@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/i2c/busses/i2c-designware-master.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
--- a/drivers/i2c/busses/i2c-designware-master.c
+++ b/drivers/i2c/busses/i2c-designware-master.c
@@ -519,10 +519,16 @@ i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
/*
* Because we don't know the buffer length in the
- * I2C_FUNC_SMBUS_BLOCK_DATA case, we can't stop
- * the transaction here.
+ * I2C_FUNC_SMBUS_BLOCK_DATA case, we can't stop the
+ * transaction here. Also disable the TX_EMPTY IRQ
+ * while waiting for the data length byte to avoid the
+ * bogus interrupts flood.
*/
- if (buf_len > 0 || flags & I2C_M_RECV_LEN) {
+ if (flags & I2C_M_RECV_LEN) {
+ dev->status |= STATUS_WRITE_IN_PROGRESS;
+ intr_mask &= ~DW_IC_INTR_TX_EMPTY;
+ break;
+ } else if (buf_len > 0) {
/* more bytes to be written */
dev->status |= STATUS_WRITE_IN_PROGRESS;
break;
@@ -558,6 +564,13 @@ i2c_dw_recv_len(struct dw_i2c_dev *dev,
msgs[dev->msg_read_idx].len = len;
msgs[dev->msg_read_idx].flags &= ~I2C_M_RECV_LEN;
+ /*
+ * Received buffer length, re-enable TX_EMPTY interrupt
+ * to resume the SMBUS transaction.
+ */
+ regmap_update_bits(dev->map, DW_IC_INTR_MASK, DW_IC_INTR_TX_EMPTY,
+ DW_IC_INTR_TX_EMPTY);
+
return len;
}
Patches currently in stable-queue which might be from tamnguyenchi@xxxxxxxxxxxxxxxxxxxxxx are
queue-6.6/i2c-designware-disable-tx_empty-irq-while-waiting-for-block-length-byte.patch
