The residue calculation may provide a wrong estimation when the transfer is
started. There are possible scenarios we have to separate:
1) the transfer is not started yet; residue is equal to the total
length;
2) the transfer is just started (first chunk is ongoing); residue is
equal to the total length without already transfered bytes;
3) the transfer is ongoing and we already sent few chunks of data;
residue is equal to the total length without fully transfered chunks
and already sent bytes.
Mistakenly the calculation in cases 2) and 3) was done in the similar way and
the result is equal to -bytes that have been transfered, i.e. quite big since
size_t type can't keep negative values.
Rewrite the calculation algorithm to be one pass and have a correct result.
Besides above in case user asks for a status of the active DMA descriptor
without pausing an ongoing transfer the residue will be estimated based on the
register value, though it's still racy. Since the transfer is active the value
is continuously being changed. Here we have to read two registers at a time. To
minimize an error make those reads close to each other.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Intel integrated DMA (iDMA) 64-bit is a specific IP that is used as a part of
LPSS devices such as HSUART or SPI. The iDMA IP is attached for private
usage on each host controller independently.
While it has similarities with Synopsys DesignWare DMA, the following
distinctions doesn't allow to use the existing driver:
- 64-bit mode with corresponding changes in Hardware Linked List data structure
- many slight differences in the channel registers
Moreover this driver is based on the DMA virtual channels framework that helps
to make the driver cleaner and easy to understand.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Andy Shevchenko