linux-kernel - Re: [PATCH] i2c: cadence: Increase timeout per message if necessary

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Message-ID: <08dc1f90-586a-a47a-7c13-bce0405c13d6@xilinx.com>
Date:   Tue, 22 Mar 2022 18:18:44 +0100
From:   Michal Simek <michal.simek@...inx.com>
To:     <tanureal@...nsource.cirrus.com>,
        Michal Simek <michal.simek@...inx.com>,
        Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-i2c@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <patches@...nsource.cirrus.com>
Subject: Re: [PATCH] i2c: cadence: Increase timeout per message if necessary



On 3/22/22 16:34, tanureal@...nsource.cirrus.com wrote:
> On 3/21/22 3:57 PM, Michal Simek <michal.simek@...inx.com> wrote:
>> +Shubhrajyoti
>>
>> On 3/9/22 10:31, Lucas Tanure wrote:
>> > Timeout as 1 second sets a upper limit on the length of
>> > the transfer executed, but there is no maximum length of
>> > a write or read message set in i2c_adapter_quirks for this
>> > controller.
>>
>> nit: I would expect that you have run any test and you reached an issue.
>> Would be good to describe what exactly you have tried on which configuration 
>> to make it super clear.
>>
>> >
>> > To remove that limitation calculate the minimal time
>> > necessary, plus some wiggle room, for every message
>> > and use it instead of the default one second, if
>> > more than one second.
>> >
>> > Signed-off-by: Lucas Tanure <tanureal@...nsource.cirrus.com>
>> > ---
>> >   drivers/i2c/busses/i2c-cadence.c | 12 ++++++++++--
>> >   1 file changed, 10 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/drivers/i2c/busses/i2c-cadence.c > 
>> b/drivers/i2c/busses/i2c-cadence.c
>> > index 805c77143a0f..b4c1ad19cdae 100644
>> > --- a/drivers/i2c/busses/i2c-cadence.c
>> > +++ b/drivers/i2c/busses/i2c-cadence.c
>> > @@ -760,7 +760,7 @@ static void cdns_i2c_master_reset(struct > i2c_adapter 
>> *adap)
>> >   static int cdns_i2c_process_msg(struct cdns_i2c *id, struct i2c_msg > *msg,
>> >           struct i2c_adapter *adap)
>> >   {
>> > -    unsigned long time_left;
>> > +    unsigned long time_left, msg_timeout;
>> >       u32 reg;
>> >       id->p_msg = msg;
>> > @@ -785,8 +785,16 @@ static int cdns_i2c_process_msg(struct cdns_i2c > *id, 
>> struct i2c_msg *msg,
>> >       else
>> >           cdns_i2c_msend(id);
>> > +    /* Minimal time to execute this message */
>> > +    msg_timeout = msecs_to_jiffies((1000 * msg->len * BITS_PER_BYTE) > / 
>> id->i2c_clk);
>> > +    /* Plus some wiggle room */
>> > +    msg_timeout += msecs_to_jiffies(500);
>> > +
>> > +    if (msg_timeout < adap->timeout)
>> > +        msg_timeout = adap->timeout;
>> > +
>> >       /* Wait for the signal of completion */
>> > -    time_left = wait_for_completion_timeout(&id->xfer_done, > adap->timeout);
>> > +    time_left = wait_for_completion_timeout(&id->xfer_done, > msg_timeout);
>> >       if (time_left == 0) {
>> >           cdns_i2c_master_reset(adap);
>> >           dev_err(id->adap.dev.parent,
>>
>>
>> If my assumption is right and there is any actual issue you had please send v2 
>> and feel free to add there my:
>> Acked-by: Michal Simek <michal.simek@...inx.com>
>>
>> Thanks,
>> Michal
>>
>>
>>
> The issue happens for I2C devices that have firmware, which will send a big I2C 
> message, but the I2C controller will timeout on it.
> That happened for CS35L41 DSP firmware tests, so no particular configuration, 
> just a driver sending firmware blob over I2C.

How big is it?

M