Hello, I have a problem with my lpspi slave driver. I am using the i.mx8qmlpddr4arm2 board with Yocto Morty. I added lpspi slave support from newer kernel, in particular I am using this version of lpspi driver: https://source.codeaurora.org/external/imx/linux-imx/tree/drivers/spi/spi-fsl-lpspi.c?h=imx_4.14.78_...
To make the system work correcty in my board I have modified the interrupt service routine of the driver:
static irqreturn_t fsl_lpspi_isr(int irq, void *dev_id)
{
u32 temp_SR, temp_IER;
struct fsl_lpspi_data *fsl_lpspi = dev_id;
temp_IER = readl(fsl_lpspi->base + IMX7ULP_IER);
fsl_lpspi_intctrl(fsl_lpspi, 0);
temp_SR = readl(fsl_lpspi->base + IMX7ULP_SR);
fsl_lpspi_read_rx_fifo(fsl_lpspi);
if ((temp_SR & SR_TDF) && (temp_IER & IER_TDIE)) {
fsl_lpspi_write_tx_fifo(fsl_lpspi);
return IRQ_HANDLED;
}
if (temp_SR & SR_RDF && (temp_IER & IER_RDIE)) {
complete(&fsl_lpspi->xfer_done);
return IRQ_HANDLED;
}
return IRQ_NONE;
}
and the function write_tx_fifo:
static void fsl_lpspi_write_tx_fifo(struct fsl_lpspi_data *fsl_lpspi)
{
u8 txfifo_cnt;
u32 temp;
txfifo_cnt = readl(fsl_lpspi->base + IMX7ULP_FSR) & 0xff;
while (txfifo_cnt < fsl_lpspi->txfifosize) {
if (!fsl_lpspi->remain)
break;
fsl_lpspi->tx(fsl_lpspi);
txfifo_cnt++;
}
if (txfifo_cnt < fsl_lpspi->txfifosize) {
if (!fsl_lpspi->is_slave) {
temp = readl(fsl_lpspi->base + IMX7ULP_TCR);
temp &= ~TCR_CONTC;
writel(temp, fsl_lpspi->base + IMX7ULP_TCR);
}
fsl_lpspi_intctrl(fsl_lpspi, IER_RDIE);
} else
fsl_lpspi_intctrl(fsl_lpspi, IER_TDIE);
}
My board in slave mode can comunicate with another board, and the data received is correct, but when I perform two consecutive transfers, the words received in the second one are read one word late, I mean it seems that the transmit fifo is not loaded in time so when a word arrives I am still loading the transmit fifo and the receive interrupt do not fire. It is weird because the data is sent one word each second, which is a lot of time. I have tried with clock speed at 100k hz, 200k hz and 500k hz.
What could be the reason of this behaviour? And how could I adjust it?
Thanks a lot,
Erica
