This is a note to let you know that I've just added the patch titled spi: spi-cadence-quadspi: Fix division by zero warning to the 5.13-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: spi-spi-cadence-quadspi-fix-division-by-zero-warning-try2.patch and it can be found in the queue-5.13 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 0e85ee897858b1c7a5de53f496d016899d9639c5 Mon Sep 17 00:00:00 2001 From: Yoshitaka Ikeda <ikeda@xxxxxxxxxxxx> Date: Fri, 16 Jul 2021 14:35:13 +0000 Subject: spi: spi-cadence-quadspi: Fix division by zero warning From: Yoshitaka Ikeda <ikeda@xxxxxxxxxxxx> commit 0e85ee897858b1c7a5de53f496d016899d9639c5 upstream. Fix below division by zero warning: - The reason for dividing by zero is because the dummy bus width is zero, but if the dummy n bytes is zero, it indicates that there is no data transfer, so we can just return zero without doing any calculations. [ 0.795337] Division by zero in kernel. : [ 0.834051] [<807fd40c>] (__div0) from [<804e1acc>] (Ldiv0+0x8/0x10) [ 0.839097] [<805f0710>] (cqspi_exec_mem_op) from [<805edb4c>] (spi_mem_exec_op+0x3b0/0x3f8) Fixes: 7512eaf54190 ("spi: cadence-quadspi: Fix dummy cycle calculation when buswidth > 1") Signed-off-by: Yoshitaka Ikeda <ikeda@xxxxxxxxxxxx> Reviewed-by: Pratyush Yadav <p.yadav@xxxxxx> Link: https://lore.kernel.org/r/92eea403-9b21-2488-9cc1-664bee760c5e@xxxxxxxxxxxx Signed-off-by: Mark Brown <broonie@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/spi/spi-cadence-quadspi.c | 3 +++ 1 file changed, 3 insertions(+) --- a/drivers/spi/spi-cadence-quadspi.c +++ b/drivers/spi/spi-cadence-quadspi.c @@ -309,6 +309,9 @@ static unsigned int cqspi_calc_dummy(con { unsigned int dummy_clk; + if (!op->dummy.nbytes) + return 0; + dummy_clk = op->dummy.nbytes * (8 / op->dummy.buswidth); if (dtr) dummy_clk /= 2; Patches currently in stable-queue which might be from ikeda@xxxxxxxxxxxx are queue-5.13/spi-spi-cadence-quadspi-fix-division-by-zero-warning-try2.patch queue-5.13/spi-spi-cadence-quadspi-fix-division-by-zero-warning.patch queue-5.13/spi-spi-cadence-quadspi-revert-fix-division-by-zero-warning.patch