Hi,
Sorry, reading the raspberry CPU manual I found that it has no DMA for the UART but it has a large FIFO [1]. Some time ago I did some tests with an Arietta G25 [2] and a Ublox M8, the linux module missed various characters and I had to enable the DMA since the CPU had no FIFO.
For the record, this is what I modified in the devicetree to enable DMA in USART2
usart1: address@hidden {
pinctrl-0 = <&pinctrl_usart1>;
status ="okay";
atmel,use-dma-rx;
atmel,use-dma-tx;
};
Deven could try to connect a USB-Serial adapter on the TX line of the gps to check if it sends all the data.