rtems_binary_semaphore_post from IRQ handler

[Ярослав Лещинский]

Hello again,

still have some troubles with post/wait binary semaphore sequence. Could
someone suggest what is a right way when you're working with semaphore
inside interrupts.

I have sys call via spidev which is waiting for the binary semaphore.
Semaphore released inside the interrupt. In some cases after several
transmission I'm getting fatal: RTEMS_FATAL_SOURCE_EXCEPTION.

I'll be really appreciate for any suggestions.

BRs, Yaroslav.

On Wed, 17 Apr 2019 at 16:25, Ярослав Лещинский <midniwalker at gmail.com>
wrote:

> Hello,
>
> I wrote spidev driver for stm32l4 mcu.
>
> spi_trasfer function looks like:
>
> static int spi_transfer(
>     spi_bus *base,
>     const spi_ioc_transfer *msgs,
>     uint32_t msg_count)
> {
>     struct stm32l4_spi_bus *bus = (struct stm32l4_spi_bus *)base;
>
>     SPI_TypeDef *spix = (SPI_TypeDef *)bus->driver.spix;
>     enum spi_major_num num = get_spi_major_number(spix);
>
>     bus->msg = &msgs[0];
>     spi_bus_table[num] = bus;
>     spi_bus_table[num]->msg_count = msg_count;
>     spi_bus_table[num]->messages_left = msg_count;
>
>     int msg_error = spi_setup_trasfer(
>             spi_bus_table[num],
>             spi_bus_table[num]->msg,
>             spi_bus_table[num]->messages_left);
>
>     rtems_binary_semaphore_wait(&bus->sem);
>
>     return (msg_error == 0)? 0 : -EINVAL;
> }
>
> Transmission proceeded via SPI IRQ + DMA IRQ. In DMA IRQ handler after dma
> successfully transmitted all data I'm using rtems_binary_semaphore_post for
> corresponding semaphore.
>
>     bool bus_is_broken = (bus == NULL) ||
>                          (msg_count < bus->messages_left) ||
>                          (msg_count == 0);
>     int ret = 0;
>
>     if(bus_is_broken == true)
>     {
>         return -EINVAL;
>     }
>
>     if(msgs->cs_change == true)
>     {
>         spi_css_deselect(&bus->driver);
>     }
>
>     if(bus->messages_left > 0)
>     {
>         const size_t msg_idx = msg_count - bus->messages_left;
>         ret = spi_do_transfer(bus, msgs, msg_idx);
>
>         bus->messages_left--;
>
>         if(ret != 0)
>         {
>             rtems_binary_semaphore_post(&bus->sem);
>
>             return ret;
>         }
>     }
>     else
>     {
>         rtems_binary_semaphore_post(&bus->sem);
>     }
>
>     return ret;
>
> Currently I see that semaphore was successfully posted but control was not
> returned to spi_transfer.
>
> As I know there are can be some issues with a context switching.
> Does rtems_binary_semaphore_post know about where control should be
> returned?
>
>
> Thanks.
>
> --
> --
> Kind regards,
> *Yaroslav Leshchinsky*
>


-- 
--
Kind regards,
*Yaroslav Leshchinsky*
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