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i2c: designware: Disable TX_EMPTY irq while waiting for block length byte

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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@vger.kernel.org
Co-developed-by: Chuong Tran <chuong@os.amperecomputing.com>
Signed-off-by: Chuong Tran <chuong@os.amperecomputing.com>
Signed-off-by: Tam Nguyen <tamnguyenchi@os.amperecomputing.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
This commit is contained in:
Tam Nguyen 2023-11-02 10:30:08 +07:00 • committed by Wolfram Sang
parent ba15a14399
commit e8183fa10c
1 changed files with 16 additions and 3 deletions
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19
drivers/i2c/busses/i2c-designware-master.c
View file

@ -519,10 +519,16 @@ i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
/* /*
* Because we don't know the buffer length in the * Because we don't know the buffer length in the
* I2C_FUNC_SMBUS_BLOCK_DATA case, we can't stop * I2C_FUNC_SMBUS_BLOCK_DATA case, we can't stop the
* the transaction here. * 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 */ /* more bytes to be written */
dev->status |= STATUS_WRITE_IN_PROGRESS; dev->status |= STATUS_WRITE_IN_PROGRESS;
break; break;
@ -558,6 +564,13 @@ i2c_dw_recv_len(struct dw_i2c_dev *dev, u8 len)
msgs[dev->msg_read_idx].len = len; msgs[dev->msg_read_idx].len = len;
msgs[dev->msg_read_idx].flags &= ~I2C_M_RECV_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; return len;
} }