[PATCH v2 1/5] UBI: incorporate maximum write size

Artem Bityutskiy
2011-02-06T13:15:46Z

From: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

Incorporate MTD write buffer size into UBI device information
because UBIFS needs this field. UBI does not use it ATM, just
provides to upper layers in 'struct ubi_device_info'.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
---
drivers/mtd/ubi/build.c | 14 ++++++++++++++
drivers/mtd/ubi/kapi.c | 1 +
drivers/mtd/ubi/ubi.h | 3 +++
include/linux/mtd/ubi.h | 15 +++++++++++++++
4 files changed, 33 insertions(+), 0 deletions(-)

diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 5ebe280..f38e8de 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -690,11 +690,25 @@ static int io_init(struct ubi_device *ubi)
ubi_assert(ubi->hdrs_min_io_size <= ubi->min_io_size);
ubi_assert(ubi->min_io_size % ubi->hdrs_min_io_size == 0);

+ ubi->max_write_size = ubi->mtd->writebufsize;
+ /*
+ * Maximum write size has to be greater or equivalent to min. I/O
+ * size, and be multiple of min. I/O size.
+ */
+ if (ubi->max_write_size < ubi->min_io_size ||
+ ubi->max_write_size % ubi->min_io_size ||
+ !is_power_of_2(ubi->max_write_size)) {
+ ubi_err("bad write buffer size %d for %d min. I/O unit",
+ ubi->max_write_size, ubi->min_io_size);
+ return -EINVAL;
+ }
+
/* Calculate default aligned sizes of EC and VID headers */
ubi->ec_hdr_alsize = ALIGN(UBI_EC_HDR_SIZE, ubi->hdrs_min_io_size);
ubi->vid_hdr_alsize = ALIGN(UBI_VID_HDR_SIZE, ubi->hdrs_min_io_size);

dbg_msg("min_io_size %d", ubi->min_io_size);
+ dbg_msg("max_write_size %d", ubi->max_write_size);
dbg_msg("hdrs_min_io_size %d", ubi->hdrs_min_io_size);
dbg_msg("ec_hdr_alsize %d", ubi->ec_hdr_alsize);
dbg_msg("vid_hdr_alsize %d", ubi->vid_hdr_alsize);
diff --git a/drivers/mtd/ubi/kapi.c b/drivers/mtd/ubi/kapi.c
index 69fa4ef0..701df4f 100644
--- a/drivers/mtd/ubi/kapi.c
+++ b/drivers/mtd/ubi/kapi.c
@@ -41,6 +41,7 @@ void ubi_do_get_device_info(struct ubi_device *ubi, struct ubi_device_info *di)
di->ubi_num = ubi->ubi_num;
di->leb_size = ubi->leb_size;
di->min_io_size = ubi->min_io_size;
+ di->max_write_size = ubi->max_write_size;
di->ro_mode = ubi->ro_mode;
di->cdev = ubi->cdev.dev;
}
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 0b0149c..b789943 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -381,6 +381,8 @@ struct ubi_wl_entry;
* @bad_allowed: whether the MTD device admits of bad physical eraseblocks or
* not
* @nor_flash: non-zero if working on top of NOR flash
+ * @max_write_size: maximum amount of bytes the underlying flash can write at a
+ * time (MTD write buffer size)
* @mtd: MTD device descriptor
*
* @peb_buf1: a buffer of PEB size used for different purposes
@@ -464,6 +466,7 @@ struct ubi_device {
int vid_hdr_shift;
unsigned int bad_allowed:1;
unsigned int nor_flash:1;
+ int max_write_size;
struct mtd_info *mtd;

void *peb_buf1;
diff --git a/include/linux/mtd/ubi.h b/include/linux/mtd/ubi.h
index b31bd9e..238b32c 100644
--- a/include/linux/mtd/ubi.h
+++ b/include/linux/mtd/ubi.h
@@ -117,17 +117,32 @@ struct ubi_volume_info {
* @ubi_num: ubi device number
* @leb_size: logical eraseblock size on this UBI device
* @min_io_size: minimal I/O unit size
+ * @max_write_size: maximum amount of bytes the underlying flash can write at a
+ * time (MTD write buffer size)
* @ro_mode: if this device is in read-only mode
* @cdev: UBI character device major and minor numbers
*
* Note, @leb_size is the logical eraseblock size offered by the UBI device.
* Volumes of this UBI device may have smaller logical eraseblock size if their
* alignment is not equivalent to %1.
+ *
+ * The @max_write_size field describes flash write maximum write unit. For
+ * example, NOR flash allows for changing individual bytes, so @min_io_size is
+ * %1. However, it does not mean than NOR flash has to write data byte-by-byte.
+ * Instead, CFI NOR flashes have a write-buffer of, e.g., 64 bytes, and when
+ * writing large chunks of data, they write 64-bytes at a time. Obviously, this
+ * improves write throughput.
+ *
+ * The @max_write_size field is always greater or equivalent to @min_io_size.
+ * E.g., some NOR flashes may have (@min_io_size = 1, @max_write_size = 64). In
+ * contrast, NAND flashes usually have @min_io_size = @max_write_size = NAND
+ * page size.
*/
struct ubi_device_info {
int ubi_num;
int leb_size;
int min_io_size;
+ int max_write_size;
int ro_mode;
dev_t cdev;
};
--
1.7.2.3