linux-kernel - Re: [linux-sunxi] [PATCH 1/5] spi: sunxi: fix transfer timeout

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Message-ID: <CAGRGNgW=UnmwwiREV+nVcws6sk18-4fKz3qf-WKf4LY9-VqBKg@mail.gmail.com>
Date:	Fri, 27 May 2016 15:10:11 +1000
From:	Julian Calaby <julian.calaby@...il.com>
To:	Michal Suchanek <hramrach@...il.com>
Cc:	linux-sunxi <linux-sunxi@...glegroups.com>,
	Mark Brown <broonie@...nel.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Chen-Yu Tsai <wens@...e.org>,
	linux-spi <linux-spi@...r.kernel.org>,
	"Mailing List, Arm" <linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [linux-sunxi] [PATCH 1/5] spi: sunxi: fix transfer timeout

Hi Michal,

On Fri, May 27, 2016 at 3:05 PM, Michal Suchanek <hramrach@...il.com> wrote:
> On 27 May 2016 at 04:05, Julian Calaby <julian.calaby@...il.com> wrote:
>> Hi Michal,
>>
>> On Fri, May 27, 2016 at 5:25 AM, Michal Suchanek <hramrach@...il.com> wrote:
>>> The trasfer timeout is fixed at 1000 ms. Reading a 4Mbyte flash over
>>> 1MHz SPI bus takes way longer than that. Calculate the timeout from the
>>> actual time the transfer is supposed to take and multiply by 2 for good
>>> measure.
>>>
>>> Signed-off-by: Michal Suchanek <hramrach@...il.com>
>>> ---
>>>
>>> v2:
>>> - fix build error
>>> - use unsigned instead of int in max_t
>>> - use tfr->speed_hz instead of sspi->max_speed_hz
>>> ---
>>>  drivers/spi/spi-sun4i.c | 11 ++++++++++-
>>>  drivers/spi/spi-sun6i.c | 11 ++++++++++-
>>>  2 files changed, 20 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/spi/spi-sun4i.c b/drivers/spi/spi-sun4i.c
>>> index 1ddd9e2..fe63bbd 100644
>>> --- a/drivers/spi/spi-sun4i.c
>>> +++ b/drivers/spi/spi-sun4i.c
>>> @@ -173,6 +173,7 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
>>>  {
>>>         struct sun4i_spi *sspi = spi_master_get_devdata(master);
>>>         unsigned int mclk_rate, div, timeout;
>>> +       unsigned int start, end, tx_time;
>>>         unsigned int tx_len = 0;
>>>         int ret = 0;
>>>         u32 reg;
>>> @@ -279,9 +280,17 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
>>>         reg = sun4i_spi_read(sspi, SUN4I_CTL_REG);
>>>         sun4i_spi_write(sspi, SUN4I_CTL_REG, reg | SUN4I_CTL_XCH);
>>>
>>> +       tx_time = max_t(unsigned, tfr->len * 8 * 2 / (tfr->speed_hz / 1000),
>>
>> You should probably use "unsigned int" instead of just "unsigned" here.
>>
>>> +                       100);
>
> Or just 100U constant and avoid max_t altogether.
>
>>> +       start = jiffies;
>>>         timeout = wait_for_completion_timeout(&sspi->done,
>>> -                                             msecs_to_jiffies(1000));
>>> +                                             msecs_to_jiffies(tx_time));
>>> +       end = jiffies;
>>>         if (!timeout) {
>>> +               dev_warn(&master->dev,
>>> +                        "%s: timeout transferring %u bytes@...z for %i(%i)ms",
>>> +                        dev_name(&spi->dev), tfr->len, tfr->speed_hz,
>>> +                        jiffies_to_msecs(end - start), tx_time);
>>
>> Should the debug changes be in a separate patch?
>
> Is this so big of a change that it needs to be split?

Some people get touchy about changes not being mentioned in the commit
log. Technically this is two changes: fixing the timeout and adding
the timeout debugging, however they're related, so maybe just mention
that you've added this debugging in the commit log.

>
>>
>>>                 ret = -ETIMEDOUT;
>>>                 goto out;
>>>         }
>>> diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
>>> index 42e2c4b..8be5c5c 100644
>>> --- a/drivers/spi/spi-sun6i.c
>>> +++ b/drivers/spi/spi-sun6i.c
>>> @@ -162,6 +162,7 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
>>>         unsigned int mclk_rate, div, timeout;
>>>         unsigned int tx_len = 0;
>>>         int ret = 0;
>>> +       unsigned int start, end, tx_time;
>>>         u32 reg;
>>>
>>>         /* We don't support transfer larger than the FIFO */
>>> @@ -269,9 +270,17 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
>>>         reg = sun6i_spi_read(sspi, SUN6I_TFR_CTL_REG);
>>>         sun6i_spi_write(sspi, SUN6I_TFR_CTL_REG, reg | SUN6I_TFR_CTL_XCH);
>>>
>>> +       tx_time = max_t(unsigned, tfr->len * 8 * 2 / (tfr->speed_hz / 1000),
>>
>> Ditto, "unsigned int" instead of "unsigned"?
>>
>>> +                       100);
>>> +       start = jiffies;
>>>         timeout = wait_for_completion_timeout(&sspi->done,
>>> -                                             msecs_to_jiffies(1000));
>>> +                                             msecs_to_jiffies(tx_time));
>>> +       end = jiffies;
>>>         if (!timeout) {
>>> +               dev_warn(&master->dev,
>>> +                        "%s: timeout transferring %u bytes@...z for %i(%i)ms",
>>> +                        dev_name(&spi->dev), tfr->len, tfr->speed_hz,
>>> +                        jiffies_to_msecs(end - start), tx_time);
>>
>> Ditto, separate patch?
>>
>> Also, should the changes for the drivers be in two separate patches also?
>
> That's basically the same driver with different constants so I guess not.

Fair enough, I withdraw my comment then.

Thanks,

-- 
Julian Calaby

Email: julian.calaby@...il.com
Profile: http://www.google.com/profiles/julian.calaby/