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

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Date:	Fri, 27 May 2016 07:05:12 +0200
From:	Michal Suchanek <hramrach@...il.com>
To:	Julian Calaby <julian.calaby@...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

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?

>
>>                 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.

Thanks

Michal