dm: spi: prevent setting a speed of 0 Hz

When the device tree is missing a correct spi slave description below
the bus (compatible "spi-flash" or spi-max-frequency are missing),
the 'set_speed' callback can be called with 'speed' == 0 Hz.
At least with cadence qspi, this leads to a division by zero.

Prevent this by initializing speed to 100 kHz in this case (same
fallback value as is done in 'dm_spi_claim_bus') and issue a warning
to console.

Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

diff --git a/drivers/spi/spi-uclass.c b/drivers/spi/spi-uclass.c
index b84255bd27439d7bb6f86bdb1fda3d7d31d565d2..2bc289a74ccb57a28e4e27c22689bca85fdb1a4f 100644 (file)
--- a/drivers/spi/spi-uclass.c
+++ b/drivers/spi/spi-uclass.c
@@ -15,6 +15,8 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
+#define SPI_DEFAULT_SPEED_HZ 100000
+
 static int spi_set_speed_mode(struct udevice *bus, int speed, int mode)
 {
        struct dm_spi_ops *ops;
@@ -58,7 +60,7 @@ int dm_spi_claim_bus(struct udevice *dev)
                        speed = spi->max_hz;
        }
        if (!speed)
-               speed = 100000;
+               speed = SPI_DEFAULT_SPEED_HZ;
        if (speed != slave->speed) {
                int ret = spi_set_speed_mode(bus, speed, slave->mode);
 
@@ -300,7 +302,13 @@ int spi_get_bus_and_cs(int busnum, int cs, int speed, int mode,
                }
                plat = dev_get_parent_platdata(dev);
                plat->cs = cs;
-               plat->max_hz = speed;
+               if (speed) {
+                       plat->max_hz = speed;
+               } else {
+                       printf("Warning: SPI speed fallback to %u kHz\n",
+                              SPI_DEFAULT_SPEED_HZ / 1000);
+                       plat->max_hz = SPI_DEFAULT_SPEED_HZ;
+               }
                plat->mode = mode;
                created = true;
        } else if (ret) {
@@ -374,7 +382,8 @@ int spi_slave_ofdata_to_platdata(struct udevice *dev,
        int value;
 
        plat->cs = dev_read_u32_default(dev, "reg", -1);
-       plat->max_hz = dev_read_u32_default(dev, "spi-max-frequency", 0);
+       plat->max_hz = dev_read_u32_default(dev, "spi-max-frequency",
+                                           SPI_DEFAULT_SPEED_HZ);
        if (dev_read_bool(dev, "spi-cpol"))
                mode |= SPI_CPOL;
        if (dev_read_bool(dev, "spi-cpha"))