[PATCH 0/5] spi: fix division by zero with a zero transfer speed

[<shao.mingyin@zte.com.cn>]

Five SPI controller drivers compute a clock divider from the transfer
speed without checking that it is non-zero.  A SPI device whose
max_speed_hz is zero (a DT node without spi-max-frequency, or a device
created through the spidev sysfs new_device interface without a speed)
therefore reaches the division with speed_hz == 0.  The SPI core clamps
such a device to the controller limit only when host->max_speed_hz is
set, and none of these five drivers sets it.

The series is organized by driver and is independent patch-by-patch;
each patch can be applied and reviewed on its own, and taking a subset
is fine:

  1/5 spi: sifive: fix division by zero in clock divisor calculation
  2/5 spi: bcm63xx-hsspi: fix division by zero for devices without a max speed
  3/5 spi: bcmbca-hsspi: fix division by zero for devices without a max speed
  4/5 spi: apple: fix division by zero in clock divisor calculation
  5/5 spi: atmel: fix division by zero when transfer speed is zero

All five clamp the divisor to 1 Hz, the same approach as the recent
spi-jcore fix.  The division does not trap on the SoCs these drivers run
on: depending on the architecture it produces a bogus divider, a zero
quotient or an undefined value, so the patches remove undefined
arithmetic rather than a crash.

Shao Mingyin (5):
  spi: sifive: fix division by zero in clock divisor calculation
  spi: bcm63xx-hsspi: fix division by zero for devices without a max speed
  spi: bcmbca-hsspi: fix division by zero for devices without a max speed
  spi: apple: fix division by zero in clock divisor calculation
  spi: atmel: fix division by zero when transfer speed is zero

 drivers/spi/spi-apple.c         | 6 +++++-
 drivers/spi/spi-atmel.c         | 3 ++-
 drivers/spi/spi-bcm63xx-hsspi.c | 3 +++
 drivers/spi/spi-bcmbca-hsspi.c  | 3 +++
 drivers/spi/spi-sifive.c        | 6 +++++-
 5 files changed, 18 insertions(+), 3 deletions(-)

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base-commit: 7649ba73f9e7e1e04d0b46213e39c79ae09dd55c