linux-kernel - Re: [PATCH v1] i2c: designware: Disable TX_EMPTY irq while waiting for block length byte

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Message-ID: <d227ba4b-2078-5b84-363b-3b26b0a2e10e@amperemail.onmicrosoft.com>
Date:   Mon, 16 Oct 2023 09:51:01 +0700
From:   Tam Chi Nguyen <tamnguyenchi@...eremail.onmicrosoft.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Tam Nguyen <tamnguyenchi@...amperecomputing.com>
Cc:     linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        patches@...erecomputing.com, jarkko.nikula@...ux.intel.com,
        mika.westerberg@...ux.intel.com, jsd@...ihalf.com,
        chuong@...amperecomputing.com, darren@...amperecomputing.com,
        stable@...r.kernel.org
Subject: Re: [PATCH v1] i2c: designware: Disable TX_EMPTY irq while waiting
 for block length byte


On 10/3/2023 15:57, Andy Shevchenko wrote:
> On Fri, Sep 29, 2023 at 10:53:56AM +0700, Tam Nguyen wrote:
>> 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 DW receives first data
> IRQ
> DesignWare
Got that. I will update in V2.
>> byte from I2C device, then re-enable it.
>>
>> 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.
> i2c_dw_isr()
Will update in V2.
>
>> And it is none after applying the patch.
>> Cc: stable@...r.kernel.org
>> Signed-off-by: Chuong Tran <chuong@...amperecomputing.com>
> Who is this guy? Do you need Co-developed-by tag?
Right, that's my bad. I will update it with "Co-developed-by" tag
>> Signed-off-by: Tam Nguyen <tamnguyenchi@...amperecomputing.com>
> Other than that, agree with Serge's points.
Thanks both of you. I totally agree with Serge's points and will update 
them in v2.
>