spi-imx: prevent overflow when estimating transfer time

The words delay is computed by multiplying two unsigned ints
and by adding up the result to a u64 variable.

The multiplication, however, is performed with 32bit math
thus losing data when the actual result is larger than UINT32_MAX.

Fix the operation by casting the first operand to u64, thus forcing
the multiplication to be performed with 64bit math.

This fixes 1 OVERFLOW_BEFORE_WIDEN issue reported by Coverity
Report: CID 1601859:  Integer handling issues  (OVERFLOW_BEFORE_WIDEN)

Cc: Mark Brown <[email protected]>
Cc: Shawn Guo <[email protected]>
Cc: Sascha Hauer <[email protected]>
Cc: Pengutronix Kernel Team <[email protected]>
Cc: Fabio Estevam <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Antonio Quartulli <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Mark Brown <[email protected]>

Author: ordex

drivers/spi/spi-imx.c

@@ -1685,7 +1685,7 @@ static unsigned int spi_imx_transfer_estimate_time_us(struct spi_transfer *trans
 		words = DIV_ROUND_UP(transfer->len * BITS_PER_BYTE, transfer->bits_per_word);
 		word_delay_us = DIV_ROUND_CLOSEST(spi_delay_to_ns(&transfer->word_delay, transfer),
 						  NSEC_PER_USEC);
-		result += words * word_delay_us;
+		result += (u64)words * word_delay_us;
 	}
 
 	return min(result, U32_MAX);