From 8e4d3d8a5e51e07bd0d6cdd81b5e4af79f796927 Mon Sep 17 00:00:00 2001 From: Raju Rangoju Date: Thu, 24 Apr 2025 17:43:33 +0530 Subject: [PATCH] spi: spi-mem: Add fix to avoid divide error For some SPI flash memory operations, dummy bytes are not mandatory. For example, in Winbond SPINAND flash memory devices, the `write_cache` and `update_cache` operation variants have zero dummy bytes. Calculating the duration for SPI memory operations with zero dummy bytes causes a divide error when `ncycles` is calculated in the spi_mem_calc_op_duration(). Add changes to skip the 'ncylcles' calculation for zero dummy bytes. Following divide error is fixed by this change: Oops: divide error: 0000 [#1] PREEMPT SMP NOPTI ... ? do_trap+0xdb/0x100 ? do_error_trap+0x75/0xb0 ? spi_mem_calc_op_duration+0x56/0xb0 ? exc_divide_error+0x3b/0x70 ? spi_mem_calc_op_duration+0x56/0xb0 ? asm_exc_divide_error+0x1b/0x20 ? spi_mem_calc_op_duration+0x56/0xb0 ? spinand_select_op_variant+0xee/0x190 [spinand] spinand_match_and_init+0x13e/0x1a0 [spinand] spinand_manufacturer_match+0x6e/0xa0 [spinand] spinand_probe+0x357/0x7f0 [spinand] ? kernfs_activate+0x87/0xd0 spi_mem_probe+0x7a/0xb0 spi_probe+0x7d/0x130 Fixes: 226d6cb3cb79 ("spi: spi-mem: Estimate the time taken by operations") Suggested-by: Krishnamoorthi M Co-developed-by: Akshata MukundShetty Signed-off-by: Akshata MukundShetty Signed-off-by: Raju Rangoju Link: https://patch.msgid.link/20250424121333.417372-1-Raju.Rangoju@amd.com Reviewed-by: Miquel Raynal Signed-off-by: Mark Brown --- drivers/spi/spi-mem.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c index a31a1db07aa4..5db0639d3b01 100644 --- a/drivers/spi/spi-mem.c +++ b/drivers/spi/spi-mem.c @@ -596,7 +596,11 @@ u64 spi_mem_calc_op_duration(struct spi_mem_op *op) ns_per_cycles = 1000000000 / op->max_freq; ncycles += ((op->cmd.nbytes * 8) / op->cmd.buswidth) / (op->cmd.dtr ? 2 : 1); ncycles += ((op->addr.nbytes * 8) / op->addr.buswidth) / (op->addr.dtr ? 2 : 1); - ncycles += ((op->dummy.nbytes * 8) / op->dummy.buswidth) / (op->dummy.dtr ? 2 : 1); + + /* Dummy bytes are optional for some SPI flash memory operations */ + if (op->dummy.nbytes) + ncycles += ((op->dummy.nbytes * 8) / op->dummy.buswidth) / (op->dummy.dtr ? 2 : 1); + ncycles += ((op->data.nbytes * 8) / op->data.buswidth) / (op->data.dtr ? 2 : 1); return ncycles * ns_per_cycles;