linux-kernel - [PATCH 2/2] nvmem: Handle reading nbits from cells with word

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Date:   Sat, 12 Nov 2022 13:04:47 +0100
From:   Sven Peter <sven@...npeter.dev>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     Sven Peter <sven@...npeter.dev>, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] nvmem: Handle reading nbits from cells with word_size > 8 correctly

Some nvmem controllers like Apple's eFuses or Nintendo's OTP have a cell
word size that's larger than one byte and cannot read anything smaller.
Round up cell->bytes correctly when accessing a subset of bits.

Signed-off-by: Sven Peter <sven@...npeter.dev>
---
 drivers/nvmem/core.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index a5b8d6989f8e..6906de15b9b8 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -470,8 +470,8 @@ static int nvmem_cell_info_to_nvmem_cell_entry_nodup(struct nvmem_device *nvmem,
 	cell->np = info->np;
 
 	if (cell->nbits)
-		cell->bytes = DIV_ROUND_UP(cell->nbits + cell->bit_offset,
-					   BITS_PER_BYTE);
+		cell->bytes = round_up(DIV_ROUND_UP(cell->nbits + cell->bit_offset,
+					   BITS_PER_BYTE), nvmem->word_size);
 
 	if (!IS_ALIGNED(cell->offset, nvmem->stride)) {
 		dev_err(&nvmem->dev,
@@ -718,9 +718,9 @@ static int nvmem_add_cells_from_of(struct nvmem_device *nvmem)
 		}
 
 		if (cell->nbits)
-			cell->bytes = DIV_ROUND_UP(
+			cell->bytes = round_up(DIV_ROUND_UP(
 					cell->nbits + cell->bit_offset,
-					BITS_PER_BYTE);
+					BITS_PER_BYTE), nvmem->word_size);
 
 		if (!IS_ALIGNED(cell->offset, nvmem->stride)) {
 			dev_err(dev, "cell %s unaligned to nvmem stride %d\n",
-- 
2.25.1