[U-Boot] [PATCH 2/2 V3] spi: exynos: Support a delay after deactivate

[Simon Glass]

Hi Jagan,

On Wed, Jun 12, 2013 at 12:51 PM, Jagan Teki <jagannadh.teki at gmail.com>wrote:

> Hi,
>
>
> On 30-05-2013 10:49, Rajeshwari Shinde wrote:
>
>> For devices that need some time to react after a spi transaction
>> finishes, add the ability to set a delay.
>>
>> Implement this as a delay on the first/next transaction to avoid
>> any delay in the fairly common case where a SPI transaction is
>> followed by other processing.
>>
>> Based on:
>> "[U-Boot] [PATCH 0/2 V5] spi: Enable SPI_PREAMBLE Mode"
>>
>
> Please use the below format for referring previous commits
> ex:
> "<PREVIOUS_COMMIT_HEAD>"
> (sha1: PREVIOUS_COMMIT_ID)
>
> in this case
> "spi: exynos: Support SPI_PREAMBLE mode"
> (sha1: e4eaef8910df805d511b1cb9b2caaf**a7d2827fdc)


I hope you don't mind me answering part of this...


>
>
>
>> Signed-off-by: Simon Glass <sjg at chromium.org>
>> Signed-off-by: Rajeshwari Shinde <rajeshwari.s at samsung.com>
>> ---
>> Changes in V2:
>>         - None.
>> Changes in V3:
>>         - Rebased on "[PATCH 0/2 V5] spi: Enable SPI_PREAMBLE Mode"
>>   drivers/spi/exynos_spi.c |   19 +++++++++++++++++++
>>   1 files changed, 19 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/spi/exynos_spi.c b/drivers/spi/exynos_spi.c
>> index 01378d0..03cf503 100644
>> --- a/drivers/spi/exynos_spi.c
>> +++ b/drivers/spi/exynos_spi.c
>> @@ -38,6 +38,7 @@ struct spi_bus {
>>         struct exynos_spi *regs;
>>         int inited;             /* 1 if this bus is ready for use */
>>         int node;
>> +       uint deactivate_delay_us;       /* Delay to wait after deactivate
>> */
>>   };
>>
>>   /* A list of spi buses that we know about */
>> @@ -52,6 +53,8 @@ struct exynos_spi_slave {
>>         enum periph_id periph_id;       /* Peripheral ID for this device
>> */
>>         unsigned int fifo_size;
>>         int skip_preamble;
>> +       struct spi_bus *bus;            /* Pointer to our SPI bus info */
>> +       ulong last_transaction_us;      /* Time of last transaction end */
>>   };
>>
>>   static struct spi_bus *spi_get_bus(unsigned dev_index)
>> @@ -97,6 +100,7 @@ struct spi_slave *spi_setup_slave(unsigned int busnum,
>> unsigned int cs,
>>         }
>>
>>         bus = &spi_bus[busnum];
>> +       spi_slave->bus = bus;
>>         spi_slave->regs = bus->regs;
>>         spi_slave->mode = mode;
>>         spi_slave->periph_id = bus->periph_id;
>> @@ -107,6 +111,7 @@ struct spi_slave *spi_setup_slave(unsigned int
>> busnum, unsigned int cs,
>>                 spi_slave->fifo_size = 256;
>>
>>         spi_slave->skip_preamble = 0;
>> +       spi_slave->last_transaction_us = timer_get_us();
>>
>>         spi_slave->freq = bus->frequency;
>>         if (max_hz)
>> @@ -371,9 +376,21 @@ void spi_cs_activate(struct spi_slave *slave)
>>   {
>>         struct exynos_spi_slave *spi_slave = to_exynos_spi(slave);
>>
>> +       /* If it's too soon to do another transaction, wait */
>> +       if (spi_slave->bus->deactivate_**delay_us &&
>> +           spi_slave->last_transaction_**us) {
>> +               ulong delay_us;         /* The delay completed so far */
>> +               delay_us = timer_get_us() - spi_slave->last_transaction_*
>> *us;
>> +               if (delay_us < spi_slave->bus->deactivate_**delay_us)
>> +                       udelay(spi_slave->bus->**deactivate_delay_us -
>> delay_us);
>> +       }
>>
> Add one space
>
>
>          clrbits_le32(&spi_slave->regs-**>cs_reg, SPI_SLAVE_SIG_INACT);
>>         debug("Activate CS, bus %d\n", spi_slave->slave.bus);
>>         spi_slave->skip_preamble = spi_slave->mode & SPI_PREAMBLE;
>> +
>> +       /* Remember time of this transaction so we can honour the bus
>> delay */
>> +       if (spi_slave->bus->deactivate_**delay_us)
>> +               spi_slave->last_transaction_us = timer_get_us();
>>   }
>>
>>   /**
>> @@ -423,6 +440,8 @@ static int spi_get_config(const void *blob, int node,
>> struct spi_bus *bus)
>>         /* Use 500KHz as a suitable default */
>>         bus->frequency = fdtdec_get_int(blob, node, "spi-max-frequency",
>>                                         500000);
>> +       bus->deactivate_delay_us = fdtdec_get_int(blob, node,
>> +                                       "spi-deactivate-delay", 0);
>>
>>         return 0;
>>   }
>>
>>
> Was this tested, usually what is the max deactivate delay?
>

This was tested with 50us.


> In this case your are passing through dts is it?
>

Yes that's right.

Regards,
Simon


>
> Thanks,
> Jagan.
>
>
>