spi: spi-bcm2835: Fix deadlock

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>

diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
index 5f8771fe1a31d08dded2d666c12127d510f233fc..775c0bf2f923d4818fc940e9b0eb11555862d7d4 100644 (file)
--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -83,6 +83,7 @@ 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
@@ -116,6 +117,7 @@ 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;
@@ -1045,19 +1047,18 @@ static int bcm2835_spi_transfer_one(struct spi_controller *ctlr,
 {
        struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
        struct bcm2835_spidev *slv = spi_get_ctldata(spi);
-       unsigned long spi_hz, clk_hz, cdiv;
+       unsigned long spi_hz, cdiv;
        unsigned long hz_per_byte, byte_limit;
        u32 cs = slv->prepare_cs;
 
        /* 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)
@@ -1065,7 +1066,7 @@ 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 */
@@ -1354,6 +1355,7 @@ 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)