linux-kernel - [RFC PATCH 2/3] mtd: rawnand: Support non-power-of-two chip sizes

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Message-Id: <20221229190906.6467-3-samuel@sholland.org>
Date:   Thu, 29 Dec 2022 13:09:04 -0600
From:   Samuel Holland <samuel@...lland.org>
To:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>
Cc:     linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Samuel Holland <samuel@...lland.org>
Subject: [RFC PATCH 2/3] mtd: rawnand: Support non-power-of-two chip sizes

Some NAND chips have a number of pages that is not exactly a power of
two. Support this by calculating the shifts and masks for the next
larger power of two.

Signed-off-by: Samuel Holland <samuel@...lland.org>
---

 drivers/mtd/nand/raw/nand_base.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index c3cc66039925..f46bad7796ed 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -5003,6 +5003,7 @@ static int nand_detect(struct nand_chip *chip, struct nand_flash_dev *type)
 	u8 *id_data = chip->id.data;
 	u8 maf_id, dev_id;
 	u64 targetsize;
+	u32 chip_page_shift;
 
 	/*
 	 * Let's start by initializing memorg fields that might be left
@@ -5148,18 +5149,13 @@ static int nand_detect(struct nand_chip *chip, struct nand_flash_dev *type)
 	chip->page_shift = ffs(mtd->writesize) - 1;
 	/* Convert chipsize to number of pages per chip -1 */
 	targetsize = nanddev_target_size(&chip->base);
-	chip->pagemask = (targetsize >> chip->page_shift) - 1;
+	chip_page_shift = order_base_2(targetsize >> chip->page_shift);
+	chip->pagemask = BIT(chip_page_shift) - 1;
 
 	chip->bbt_erase_shift = chip->phys_erase_shift =
 		ffs(mtd->erasesize) - 1;
-	if (targetsize & 0xffffffff)
-		chip->chip_shift = ffs((unsigned)targetsize) - 1;
-	else {
-		chip->chip_shift = ffs((unsigned)(targetsize >> 32));
-		chip->chip_shift += 32 - 1;
-	}
-
-	if (chip->chip_shift - chip->page_shift > 16)
+	chip->chip_shift = chip_page_shift + chip->page_shift;
+	if (chip_page_shift > 16)
 		chip->options |= NAND_ROW_ADDR_3;
 
 	chip->badblockbits = 8;
-- 
2.37.4