spi: davinci: Unset POWERDOWN bit when releasing resources

On the OMAPL138, the SPI reference clock is provided by the Power and
Sleep Controller (PSC). The PSC's datasheet says that 'some peripherals
have special programming requirements and additional recommended steps
you must take before you can invoke the PSC module state transition'. I
didn't find more details in documentation but it appears that PSC needs
the SPI to clear the POWERDOWN bit before disabling the clock. Indeed,
when this bit is set, the PSC gets stuck in transitions from enable to
disable state.

Clear the POWERDOWN bit when releasing driver's resources

Signed-off-by: Bastien Curutchet <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Mark Brown <[email protected]>

Author: bastien-curutchet

drivers/spi/spi-davinci.c

@@ -984,6 +984,9 @@ static int davinci_spi_probe(struct platform_device *pdev)
 	return ret;
 
 free_dma:
+	/* This bit needs to be cleared to disable dpsi->clk */
+	clear_io_bits(dspi->base + SPIGCR1, SPIGCR1_POWERDOWN_MASK);
+
 	if (dspi->dma_rx) {
 		dma_release_channel(dspi->dma_rx);
 		dma_release_channel(dspi->dma_tx);
@@ -1013,6 +1016,9 @@ static void davinci_spi_remove(struct platform_device *pdev)
 
 	spi_bitbang_stop(&dspi->bitbang);
 
+	/* This bit needs to be cleared to disable dpsi->clk */
+	clear_io_bits(dspi->base + SPIGCR1, SPIGCR1_POWERDOWN_MASK);
+
 	if (dspi->dma_rx) {
 		dma_release_channel(dspi->dma_rx);
 		dma_release_channel(dspi->dma_tx);