I started using this driver two years ago in kernek 4.4 and then in kernel 4.9. It didn't go well from the very beginning due to my platform peculiarities: DW SPI core with hardware CS and relatively slow MIPS-based SoC. This patchset is intended to fix some of the problems I found out during the max310x driver utilization with max14830 device. First of all it was discovered, that workqueue API isn't optimally used. Work context isn't re-entrant by design, so the mutex used to guard the TX-method is redundant. schedule_work() method is also created in a way the work item is scheduled only if it isn't pending. Patch 1 concerns all these fixes. Seeing the similar container_of(uart_port) is used three times in the driver, the patch 2 introduces a macro to_max310x_port() to get a pointer to corresponding struct max310x_one. This is the code simplification and is going to be used in the following patches. It was found out, that batch read and write methods used buffers allocated on the kernel stack. Since they might be utilized by SPI controllers for DMA it might be unsafe on some platforms. Patch 3 provides a dedicated kmalloced buffers for this. The baud-rate calculator function didn't work correct for all the possible baud-rates requested within a pre-defined input reference frequency. Instead an algo fully compliant with datasheet divisor formulae is implemented in patch 4. Patches 5 and 6 are created to fix some rs485 issues. Particularly the rs485 mode is configured on the port startup if it's enabled. And seeing the mode2 register provides a way to enable/disable the echo-suppression in RS485 mode, it is used to implement the SER_RS485_RX_DURING_TX flag support. Finally it was discovered that in case if inbound hardware FIFO experienced overflow, a lot of '\0' characters inserted into the flip-buffer as a character of the RX-FIFO overrun. It isn't quite correct since the overflow happened only after the last character had been received. Patch 7 is dedicated to push only a single RX-FIFO overrun character in this case. Signed-off-by: Serge Semin <fancer.lancer@xxxxxxxxx> Serge Semin (7): tty: max310x: Simplify tx-work item code tty: max310x: Introduce max310x_one port macro-wrapper tty: max310x: Don't pass stacked buffers to SPI tty: max310x: Fix invalid baudrate divisors calculator tty: max310x: Add rx-during-tx rs485 flag support tty: max310x: Optionally enable rs485 on startup tty: max310x: Split uart characters insertion loop drivers/tty/serial/max310x.c | 157 +++++++++++++++++++++-------------- 1 file changed, 95 insertions(+), 62 deletions(-) -- 2.21.0
