On Fri, May 8, 2020 at 12:37 PM Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx> wrote: > > This SPI-controller is a part of the Baikal-T1 System Controller and > is based on the DW APB SSI IP-core, but with very limited resources: > no IRQ, no DMA, only a single native chip-select and just 8 bytes Tx/Rx > FIFO available. In order to provide a transparent initial boot code > execution this controller is also utilized by an vendor-specific block, > which provides an CS0 SPI flash direct mapping interface. Since both > direct mapping and SPI controller normal utilization are mutual exclusive > only a one of these interfaces can be used to access an external SPI > slave device. Taking into account the peculiarities of the controller > registers and physically mapped SPI flash access, very limited resources > and seeing the normal usecase of the controller is to access an external > SPI-nor flash, we decided to create a dedicated SPI driver for it. It seems a lot of code. Why can't you use spi-dw-mmio.c et al.? > The driver provides callbacks for native messages-based SPI interface, > SPI-memory and direct mapping read operations. Due to not having any > asynchronous signaling interface provided by the core we have no choice > but to implement a polling-based data transmission/reception algorithm. > In addition to that in order to bypass the automatic native chip-select > toggle the driver disables the local interrupts during the memory-based > transfers if no complementary GPIO-based chip-select detected in the > platform. -- With Best Regards, Andy Shevchenko
