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spi: spi-mtk-nor: fix timeout calculation overflow

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CLK_TO_US macro is used to calculate potential transfer time for various
timeout handling. However it overflows on transfer bigger than 512 bytes
because it first did (len * 8 * 1000000).
This controller typically operates at 45MHz. This patch did 2 things:
1. calculate clock / 1000000 first
2. add a 4M transfer size cap so that the final timeout in DMA reading
   doesn't overflow

Fixes: 881d1ee9fe ("spi: add support for mediatek spi-nor controller")
Cc: <stable@vger.kernel.org>
Signed-off-by: Chuanhong Guo <gch981213@gmail.com>
Link: https://lore.kernel.org/r/20200922114905.2942859-1-gch981213@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Chuanhong Guo 2020-09-22 19:49:02 +08:00 committed by Mark Brown
parent f09a433b1e
commit 4cafaddedb
No known key found for this signature in database
GPG Key ID: 24D68B725D5487D0
1 changed files with 5 additions and 1 deletions
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6
drivers/spi/spi-mtk-nor.c
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@ -89,7 +89,7 @@
// Buffered page program can do one 128-byte transfer
#define MTK_NOR_PP_SIZE 128
#define CLK_TO_US(sp, clkcnt) ((clkcnt) * 1000000 / sp->spi_freq)
#define CLK_TO_US(sp, clkcnt) DIV_ROUND_UP(clkcnt, sp->spi_freq / 1000000)
struct mtk_nor {
struct spi_controller *ctlr;
@ -177,6 +177,10 @@ static int mtk_nor_adjust_op_size(struct spi_mem *mem, struct spi_mem_op *op)
if ((op->addr.nbytes == 3) || (op->addr.nbytes == 4)) {
if ((op->data.dir == SPI_MEM_DATA_IN) &&
mtk_nor_match_read(op)) {
// limit size to prevent timeout calculation overflow
if (op->data.nbytes > 0x400000)
op->data.nbytes = 0x400000;
if ((op->addr.val & MTK_NOR_DMA_ALIGN_MASK) ||
(op->data.nbytes < MTK_NOR_DMA_ALIGN))
op->data.nbytes = 1;