diff mbox

[U-Boot,v1,1/4] mtd: nand: add NAND_BUSWIDTH_AUTO to autodetect bus width

Message ID 1378819628-28745-2-git-send-email-pekon@ti.com
State Superseded
Delegated to: Tom Rini
Headers show

Commit Message

pekon gupta Sept. 10, 2013, 1:27 p.m. UTC 
From: Matthieu CASTET <matthieu.castet@parrot.com>

This patch is slightly modified from following linux patch
http://lists.infradead.org/pipermail/linux-mtd/2012-November/044803.html
So retaining the authorship to Matthieu CASTET <matthieu.castet@parrot.com>
*Modifications from original patch*
reset chip->read_byte, chip->read_buf, chip->write_buf before setting defaults.

*Original patch message*
The driver call nand_scan_ident in 8 bit mode, then
readid or onfi detection are done (and detect bus width).
The driver should update its bus width before calling nand_scan_tail.

This work because readid and onfi are read work 8 byte mode.

Note that nand_scan_ident send command (NAND_CMD_RESET, NAND_CMD_READID, NAND_CMD_PARAM), address and read data
The ONFI specificication is not very clear for x16 device if high byte of address should be driven to 0,
but according to [1] it should be ok to not drive it during autodetection.

[1]
3.3.2. Target Initialization

[...]
The Read ID and Read Parameter Page commands only use the lower 8-bits of the data bus.
The host shall not issue commands that use a word data width on x16 devices until the host
determines the device supports a 16-bit data bus width in the parameter page.

Signed-off-by: Pekon Gupta <pekon@ti.com>
---
 drivers/mtd/nand/nand_base.c | 20 +++++++++++++++-----
 include/linux/mtd/nand.h     |  7 +++++++
 2 files changed, 22 insertions(+), 5 deletions(-)

Comments

Scott Wood Nov. 14, 2013, 1:37 a.m. UTC | #1 
On Tue, Sep 10, 2013 at 06:57:05PM +0530, pekon gupta wrote:
> From: Matthieu CASTET <matthieu.castet@parrot.com>
> 
> This patch is slightly modified from following linux patch
> http://lists.infradead.org/pipermail/linux-mtd/2012-November/044803.html

Which is now commit 64b37b2a63eb2f80b65c7185f0013f8ffc637ae3

> So retaining the authorship to Matthieu CASTET <matthieu.castet@parrot.com>
> *Modifications from original patch*
> reset chip->read_byte, chip->read_buf, chip->write_buf before setting defaults.

Why does U-Boot need this if Linux doesn't?

-Scott
pekon gupta Nov. 14, 2013, 4:32 a.m. UTC | #2 
> From: Scott Wood [mailto:scottwood@freescale.com]
> On Tue, Sep 10, 2013 at 06:57:05PM +0530, pekon gupta wrote:
> > From: Matthieu CASTET <matthieu.castet@parrot.com>
> >
> > This patch is slightly modified from following linux patch
> > http://lists.infradead.org/pipermail/linux-mtd/2012-
> November/044803.html
>
> Which is now commit 64b37b2a63eb2f80b65c7185f0013f8ffc637ae3
>
> > So retaining the authorship to Matthieu CASTET
> <matthieu.castet@parrot.com>
> > *Modifications from original patch*
> > reset chip->read_byte, chip->read_buf, chip->write_buf before setting
> defaults.
>
> Why does U-Boot need this if Linux doesn't?
>
Yes, I plan to drop this patch.
Reason: Though this feature was introduced in linux long back, but hardly
any mtd/nand drivers using this. Also there are alternative approaches
which do not require any change in individual controller drivers, but just
in generic NAND driver.
I have proposed them in linux mtd-maillist, I'll propose same in my next
version of patch-set.

http://lists.infradead.org/pipermail/linux-mtd/2013-November/049744.html


with regards, pekon
Scott Wood Nov. 14, 2013, 9:27 p.m. UTC | #3 
On Thu, 2013-11-14 at 04:32 +0000, Gupta, Pekon wrote:
> > From: Scott Wood [mailto:scottwood@freescale.com]
> > On Tue, Sep 10, 2013 at 06:57:05PM +0530, pekon gupta wrote:
> > > From: Matthieu CASTET <matthieu.castet@parrot.com>
> > >
> > > This patch is slightly modified from following linux patch
> > > http://lists.infradead.org/pipermail/linux-mtd/2012-
> > November/044803.html
> >
> > Which is now commit 64b37b2a63eb2f80b65c7185f0013f8ffc637ae3
> >
> > > So retaining the authorship to Matthieu CASTET
> > <matthieu.castet@parrot.com>
> > > *Modifications from original patch*
> > > reset chip->read_byte, chip->read_buf, chip->write_buf before setting
> > defaults.
> >
> > Why does U-Boot need this if Linux doesn't?
> >
> Yes, I plan to drop this patch.
> Reason: Though this feature was introduced in linux long back, but hardly
> any mtd/nand drivers using this. Also there are alternative approaches
> which do not require any change in individual controller drivers, but just
> in generic NAND driver.
> I have proposed them in linux mtd-maillist, I'll propose same in my next
> version of patch-set.
> 
> http://lists.infradead.org/pipermail/linux-mtd/2013-November/049744.html

Hmm, I don't like the "kill NAND_BUSWIDTH_AUTO" sentiment.  The device
tree is for describing things that can't be reasonably discovered
through hardware interfaces.  ONFI identification always being x8 seems
designed specifically to allow said discovery.

-Scott
diff mbox

Patch

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 9e05cef..52e799b 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -2977,11 +2977,21 @@  ident_done:
 			break;
 	}
 
-	/*
-	 * Check, if buswidth is correct. Hardware drivers should set
-	 * chip correct!
-	 */
-	if (busw != (chip->options & NAND_BUSWIDTH_16)) {
+	if (chip->options & NAND_BUSWIDTH_AUTO) {
+		WARN_ON(chip->options & NAND_BUSWIDTH_16);
+		chip->options |= busw;
+		if (chip->read_byte == nand_read_byte)
+			chip->read_byte = NULL;
+		if (chip->read_buf == nand_read_buf)
+			chip->read_buf  = NULL;
+		if (chip->write_buf == nand_write_buf)
+			chip->write_buf = NULL;
+		nand_set_defaults(chip, busw);
+	} else if (busw != (chip->options & NAND_BUSWIDTH_16)) {
+		/*
+		 * Check, if buswidth is correct. Hardware drivers should set
+		 * chip correct!
+		 */
 		pr_info("NAND device: Manufacturer ID:"
 			" 0x%02x, Chip ID: 0x%02x (%s %s)\n", *maf_id,
 			*dev_id, nand_manuf_ids[maf_idx].name, mtd->name);
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index 2055584..bd6bc25 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -211,6 +211,13 @@  typedef enum {
 #define NAND_OWN_BUFFERS	0x00020000
 /* Chip may not exist, so silence any errors in scan */
 #define NAND_SCAN_SILENT_NODEV	0x00040000
+/*
+ * Autodetect nand buswidth with readid/onfi.
+ * This suppose the driver will configure the hardware in 8 bits mode
+ * when calling nand_scan_ident, and update its configuration
+ * before calling nand_scan_tail.
+ */
+#define NAND_BUSWIDTH_AUTO      0x00080000
 
 /* Options set by nand scan */
 /* bbt has already been read */