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

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: 881d1ee ("spi: add support for mediatek spi-nor controller") Cc: <[email protected]> Signed-off-by: Chuanhong Guo <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Mark Brown <[email protected]>
ambv · Sep 25, 2020 · 4cafadd · 4cafadd
1 parent f09a433
commit 4cafadd
Showing 1 changed file with 5 additions and 1 deletion.
diff --git a/drivers/spi/spi-mtk-nor.c b/drivers/spi/spi-mtk-nor.c
@@ -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;