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Thu, 2 Nov 2023 03:30:36 +0000 From: Tam Nguyen To: linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org Cc: patches@amperecomputing.com, jarkko.nikula@linux.intel.com, andriy.shevchenko@linux.intel.com, mika.westerberg@linux.intel.com, jsd@semihalf.com, tamnguyenchi@os.amperecomputing.com, chuong@os.amperecomputing.com, darren@os.amperecomputing.com, stable@vger.kernel.org Subject: [PATCH v2] i2c: designware: Disable TX_EMPTY irq while waiting for block length byte Date: Thu, 2 Nov 2023 10:30:08 +0700 Message-Id: <20231102033009.4555-1-tamnguyenchi@os.amperecomputing.com> X-Mailer: git-send-email 2.25.1 X-ClientProxiedBy: SI2P153CA0009.APCP153.PROD.OUTLOOK.COM (2603:1096:4:140::18) To SA1PR01MB8131.prod.exchangelabs.com (2603:10b6:806:325::8) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SA1PR01MB8131:EE_|SA3PR01MB7967:EE_ X-MS-Office365-Filtering-Correlation-Id: f1e2459c-f22f-4b33-a80b-08dbdb5413b5 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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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 Signed-off-by: Chuong Tran Signed-off-by: Tam Nguyen Acked-by: Jarkko Nikula Reviewed-by: Serge Semin --- v2: + Reduce the indentations level + Use regmap_update_bits for bitfield update + Rewrite comment statement [Serge] + Update commit message + Add Co-developed-by tag for co-authors [Andy] v1: https://lore.kernel.org/lkml/avd7jhwexehgbvi6euzdwvf5zvqqgjx4ozo6uxu2qpmlarvva3@sgkce3rvovwk/T/ --- drivers/i2c/busses/i2c-designware-master.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c index 55ea91a63382..ae76620ef35e 100644 --- a/drivers/i2c/busses/i2c-designware-master.c +++ b/drivers/i2c/busses/i2c-designware-master.c @@ -456,10 +456,16 @@ 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; @@ -495,6 +501,13 @@ i2c_dw_recv_len(struct dw_i2c_dev *dev, u8 len) 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; }