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Subject[PATCH 5.10 089/167] spi: spi-bcm2835: Fix deadlock
Date
From: Alexandru Tachici <alexandru.tachici@analog.com>

[ Upstream commit c45c1e82bba130db4f19d9dbc1deefcf4ea994ed ]

The bcm2835_spi_transfer_one function can create a deadlock
if it is called while another thread already has the
CCF lock.

Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
Fixes: f8043872e796 ("spi: add driver for BCM2835")
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20210716210245.13240-2-alexandru.tachici@analog.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/spi/spi-bcm2835.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
index 29ee555a42f9..33c32e931767 100644
--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -84,6 +84,7 @@ MODULE_PARM_DESC(polling_limit_us,
* struct bcm2835_spi - BCM2835 SPI controller
* @regs: base address of register map
* @clk: core clock, divided to calculate serial clock
+ * @clk_hz: core clock cached speed
* @irq: interrupt, signals TX FIFO empty or RX FIFO ¾ full
* @tfr: SPI transfer currently processed
* @ctlr: SPI controller reverse lookup
@@ -124,6 +125,7 @@ MODULE_PARM_DESC(polling_limit_us,
struct bcm2835_spi {
void __iomem *regs;
struct clk *clk;
+ unsigned long clk_hz;
int irq;
struct spi_transfer *tfr;
struct spi_controller *ctlr;
@@ -1082,19 +1084,18 @@ static int bcm2835_spi_transfer_one(struct spi_controller *ctlr,
struct spi_transfer *tfr)
{
struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
- unsigned long spi_hz, clk_hz, cdiv;
+ unsigned long spi_hz, cdiv;
unsigned long hz_per_byte, byte_limit;
u32 cs = bs->prepare_cs[spi->chip_select];

/* set clock */
spi_hz = tfr->speed_hz;
- clk_hz = clk_get_rate(bs->clk);

- if (spi_hz >= clk_hz / 2) {
+ if (spi_hz >= bs->clk_hz / 2) {
cdiv = 2; /* clk_hz/2 is the fastest we can go */
} else if (spi_hz) {
/* CDIV must be a multiple of two */
- cdiv = DIV_ROUND_UP(clk_hz, spi_hz);
+ cdiv = DIV_ROUND_UP(bs->clk_hz, spi_hz);
cdiv += (cdiv % 2);

if (cdiv >= 65536)
@@ -1102,7 +1103,7 @@ static int bcm2835_spi_transfer_one(struct spi_controller *ctlr,
} else {
cdiv = 0; /* 0 is the slowest we can go */
}
- tfr->effective_speed_hz = cdiv ? (clk_hz / cdiv) : (clk_hz / 65536);
+ tfr->effective_speed_hz = cdiv ? (bs->clk_hz / cdiv) : (bs->clk_hz / 65536);
bcm2835_wr(bs, BCM2835_SPI_CLK, cdiv);

/* handle all the 3-wire mode */
@@ -1318,6 +1319,7 @@ static int bcm2835_spi_probe(struct platform_device *pdev)
return bs->irq ? bs->irq : -ENODEV;

clk_prepare_enable(bs->clk);
+ bs->clk_hz = clk_get_rate(bs->clk);

err = bcm2835_dma_init(ctlr, &pdev->dev, bs);
if (err)
--
2.30.2


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