Patch "spi: rockchip: fix missing error on unsupported SPI_CS_HIGH" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    spi: rockchip: fix missing error on unsupported SPI_CS_HIGH

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     spi-rockchip-fix-missing-error-on-unsupported-spi_cs.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 570099d038688de8d67e3eea5405fe47e2d51404
Author: Luca Ceresoli <luca.ceresoli@xxxxxxxxxxx>
Date:   Thu Apr 21 23:32:51 2022 +0200

    spi: rockchip: fix missing error on unsupported SPI_CS_HIGH
    
    [ Upstream commit d5d933f09ac326aebad85bfb787cc786ad477711 ]
    
    The hardware (except for the ROCKCHIP_SPI_VER2_TYPE2 version) does not
    support active-high native chip selects. However if such a CS is configured
    the core does not error as it normally should, because the
    'ctlr->use_gpio_descriptors = true' line in rockchip_spi_probe() makes the
    core set SPI_CS_HIGH in ctlr->mode_bits.
    
    In such a case the spi-rockchip driver operates normally but produces an
    active-low chip select signal without notice.
    
    There is no provision in the current core code to handle this
    situation. Fix by adding a check in the ctlr->setup function (similarly to
    what spi-atmel.c does).
    
    This cannot be done reading the SPI_CS_HIGH but in ctlr->mode_bits because
    that bit gets always set by the core for master mode (see above).
    
    Fixes: eb1262e3cc8b ("spi: spi-rockchip: use num-cs property and ctlr->enable_gpiods")
    Signed-off-by: Luca Ceresoli <luca.ceresoli@xxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20220421213251.1077899-1-luca.ceresoli@xxxxxxxxxxx
    Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c
index 83da8fdb3c02..b721b62118e1 100644
--- a/drivers/spi/spi-rockchip.c
+++ b/drivers/spi/spi-rockchip.c
@@ -196,6 +196,8 @@ struct rockchip_spi {
 
 	bool slave_abort;
 	bool cs_inactive; /* spi slave tansmition stop when cs inactive */
+	bool cs_high_supported; /* native CS supports active-high polarity */
+
 	struct spi_transfer *xfer; /* Store xfer temporarily */
 };
 
@@ -718,6 +720,11 @@ static int rockchip_spi_setup(struct spi_device *spi)
 	struct rockchip_spi *rs = spi_controller_get_devdata(spi->controller);
 	u32 cr0;
 
+	if (!spi->cs_gpiod && (spi->mode & SPI_CS_HIGH) && !rs->cs_high_supported) {
+		dev_warn(&spi->dev, "setup: non GPIO CS can't be active-high\n");
+		return -EINVAL;
+	}
+
 	pm_runtime_get_sync(rs->dev);
 
 	cr0 = readl_relaxed(rs->regs + ROCKCHIP_SPI_CTRLR0);
@@ -898,6 +905,7 @@ static int rockchip_spi_probe(struct platform_device *pdev)
 
 	switch (readl_relaxed(rs->regs + ROCKCHIP_SPI_VERSION)) {
 	case ROCKCHIP_SPI_VER2_TYPE2:
+		rs->cs_high_supported = true;
 		ctlr->mode_bits |= SPI_CS_HIGH;
 		if (ctlr->can_dma && slave_mode)
 			rs->cs_inactive = true;