linux-kernel - [PATCH AUTOSEL 6.9 02/11] spi: davinci: Unset POWERDOWN bit when releasing resources

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Message-ID: <20240716183222.2813968-2-sashal@kernel.org>
Date: Tue, 16 Jul 2024 14:31:46 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Bastien Curutchet <bastien.curutchet@...tlin.com>,
	Mark Brown <broonie@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	linux-spi@...r.kernel.org
Subject: [PATCH AUTOSEL 6.9 02/11] spi: davinci: Unset POWERDOWN bit when releasing resources

From: Bastien Curutchet <bastien.curutchet@...tlin.com>

[ Upstream commit 1762dc01fc78ef5f19693e9317eae7491c6c7e1b ]

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 <bastien.curutchet@...tlin.com>
Link: https://patch.msgid.link/20240624071745.17409-1-bastien.curutchet@bootlin.com
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/spi/spi-davinci.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/spi/spi-davinci.c b/drivers/spi/spi-davinci.c
index be3998104bfbb..f7e8b5efa50e5 100644
--- a/drivers/spi/spi-davinci.c
+++ b/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);
-- 
2.43.0