From 44476137e3522744c076aca3615597e2f2845305 Mon Sep 17 00:00:00 2001
From: Benjamin Valentin <benjamin.valentin@ml-pa.com>
Date: Mon, 6 Feb 2023 15:46:34 +0100
Subject: [PATCH] mtd: add fast path to mtd_write_page()

If we overwrite a whole sector, don't perform a read-modify-write cycle.
---
 drivers/mtd/mtd.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/mtd/mtd.c b/drivers/mtd/mtd.c
index 030b3f8fba..e7793e9f51 100644
--- a/drivers/mtd/mtd.c
+++ b/drivers/mtd/mtd.c
@@ -183,6 +183,12 @@ static size_t _write_sector(mtd_dev_t *mtd, const void *data, uint32_t sector,
         len = sector_size - offset;
     }
 
+    /* fast path: skip reading the sector if we overwrite it completely */
+    if (offset == 0 && len == sector_size) {
+        work = (void *)data;
+        goto write;
+    }
+
     /* copy sector to RAM */
     res = mtd_read_page(mtd, work, sector_page, 0, sector_size);
     if (res < 0) {
@@ -198,6 +204,7 @@ static size_t _write_sector(mtd_dev_t *mtd, const void *data, uint32_t sector,
     /* modify sector in RAM */
     memcpy(work + offset, data, len);
 
+write:
     /* write back modified sector copy */
     res = mtd_write_page_raw(mtd, work, sector_page, 0, sector_size);
     if (res < 0) {