Patchwork [v2] mtd: omap: nand: Remove 0xFF's that prefixed 16bit NAND commands

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Submitter Christopher Harvey
Date Oct. 26, 2012, 7:36 p.m.
Message ID <20121026193643.GA21510@harvey-pc.matrox.com>
Download mbox | patch
Permalink /patch/194557/
State New
Headers show

Comments

Christopher Harvey - Oct. 26, 2012, 7:36 p.m.
In 16bit NAND mode the GPMC would send the command 0xNN as 0xFFNN
instead of 0x00NN on the bus. The 0xFFs were actually uninitialized
bits that were left unset in the GPMC command output register. The
reason they weren't initialized in 16bit mode is that if the same code
that writes to this register was used in 8bit mode then 2 commands
would be output in 8bit mode. One for the low byte, and an extra 0x0
command for the high byte. This commit uses writew if we're using
16bit NAND.

Most chips seem fine with the extra 0xFFs, but the ONFI spec says
otherwise.

Signed-off-by: Christopher Harvey <charvey@matrox.com>
---
 drivers/mtd/nand/omap2.c |   14 +++++++++-----
 1 files changed, 9 insertions(+), 5 deletions(-)
Ivan Djelic - Oct. 29, 2012, 1:49 p.m.
On Fri, Oct 26, 2012 at 08:36:43PM +0100, Christopher Harvey wrote:
> In 16bit NAND mode the GPMC would send the command 0xNN as 0xFFNN
> instead of 0x00NN on the bus. The 0xFFs were actually uninitialized
> bits that were left unset in the GPMC command output register. The
> reason they weren't initialized in 16bit mode is that if the same code
> that writes to this register was used in 8bit mode then 2 commands
> would be output in 8bit mode. One for the low byte, and an extra 0x0
> command for the high byte. This commit uses writew if we're using
> 16bit NAND.
> 
> Most chips seem fine with the extra 0xFFs, but the ONFI spec says
> otherwise.

Hi Christopher,

Nitpick: I think you should replace 'command' with 'address' in your commit message.
The ONFI spec says Host should send _address_ byte NN as 0x00NN. It is OK to send
command NN as 0xFFNN, as explicitly mentioned in ONFI 3.1 spec (section 2.16):

  2.16.          Bus Width Requirements
All NAND Targets per device shall use the same data bus width. All targets shall either have an
8-bit bus width or a 16-bit bus width. Note that devices that support the NV-DDR or NV-DDR2
data interface shall have an 8-bit bus width.
When the host supports a 16-bit bus width, only data is transferred at the 16-bit width. All
address and command line transfers shall use only the lower 8-bits of the data bus. During
command transfers, the host may place any value on the upper 8-bits of the data bus. During
address transfers, the host shall set the upper 8-bits of the data bus to 00h.

Your patch deals with both command and address bytes, which does not hurt.
BR,
--
Ivan

> 
> Signed-off-by: Christopher Harvey <charvey@matrox.com>
> ---
>  drivers/mtd/nand/omap2.c |   14 +++++++++-----
>  1 files changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
> index 5b31386..ae6738f 100644
> --- a/drivers/mtd/nand/omap2.c
> +++ b/drivers/mtd/nand/omap2.c
> @@ -225,16 +225,20 @@ static void omap_hwcontrol(struct mtd_info *mtd, int cmd, unsigned int ctrl)
>  {
>  	struct omap_nand_info *info = container_of(mtd,
>  					struct omap_nand_info, mtd);
> +	void __iomem *reg;
>  
>  	if (cmd != NAND_CMD_NONE) {
>  		if (ctrl & NAND_CLE)
> -			writeb(cmd, info->reg.gpmc_nand_command);
> -
> +			reg = info->reg.gpmc_nand_command;
>  		else if (ctrl & NAND_ALE)
> -			writeb(cmd, info->reg.gpmc_nand_address);
> -
> +			reg = info->reg.gpmc_nand_address;
>  		else /* NAND_NCE */
> -			writeb(cmd, info->reg.gpmc_nand_data);
> +			reg = info->reg.gpmc_nand_data;
> +
> +		if (info->nand.options & NAND_BUSWIDTH_16)
> +			writew(cmd, reg);
> +		else
> +			writeb(cmd, reg);
>  	}
>  }
>  
> -- 
> 1.7.8.6
> 
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
Christopher Harvey - Oct. 29, 2012, 5:04 p.m.
On Mon, Oct 29, 2012 at 02:49:03PM +0100, Ivan Djelic wrote:
> On Fri, Oct 26, 2012 at 08:36:43PM +0100, Christopher Harvey wrote:
> > In 16bit NAND mode the GPMC would send the command 0xNN as 0xFFNN
> > instead of 0x00NN on the bus. The 0xFFs were actually uninitialized
> > bits that were left unset in the GPMC command output register. The
> > reason they weren't initialized in 16bit mode is that if the same code
> > that writes to this register was used in 8bit mode then 2 commands
> > would be output in 8bit mode. One for the low byte, and an extra 0x0
> > command for the high byte. This commit uses writew if we're using
> > 16bit NAND.
> > 
> > Most chips seem fine with the extra 0xFFs, but the ONFI spec says
> > otherwise.
> 
> Hi Christopher,
> 
> Nitpick: I think you should replace 'command' with 'address' in your commit message.
> The ONFI spec says Host should send _address_ byte NN as 0x00NN. It is OK to send
> command NN as 0xFFNN, as explicitly mentioned in ONFI 3.1 spec (section 2.16):
> 
>   2.16.          Bus Width Requirements
> All NAND Targets per device shall use the same data bus width. All targets shall either have an
> 8-bit bus width or a 16-bit bus width. Note that devices that support the NV-DDR or NV-DDR2
> data interface shall have an 8-bit bus width.
> When the host supports a 16-bit bus width, only data is transferred at the 16-bit width. All
> address and command line transfers shall use only the lower 8-bits of the data bus. During
> command transfers, the host may place any value on the upper 8-bits of the data bus. During
> address transfers, the host shall set the upper 8-bits of the data bus to 00h.
> 
> Your patch deals with both command and address bytes, which does not hurt.
> BR,
> --
> Ivan

Ok, makes sense. Thanks for pointing that out. I'll update the wording.

> > 
> > Signed-off-by: Christopher Harvey <charvey@matrox.com>
> > ---
> >  drivers/mtd/nand/omap2.c |   14 +++++++++-----
> >  1 files changed, 9 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
> > index 5b31386..ae6738f 100644
> > --- a/drivers/mtd/nand/omap2.c
> > +++ b/drivers/mtd/nand/omap2.c
> > @@ -225,16 +225,20 @@ static void omap_hwcontrol(struct mtd_info *mtd, int cmd, unsigned int ctrl)
> >  {
> >  	struct omap_nand_info *info = container_of(mtd,
> >  					struct omap_nand_info, mtd);
> > +	void __iomem *reg;
> >  
> >  	if (cmd != NAND_CMD_NONE) {
> >  		if (ctrl & NAND_CLE)
> > -			writeb(cmd, info->reg.gpmc_nand_command);
> > -
> > +			reg = info->reg.gpmc_nand_command;
> >  		else if (ctrl & NAND_ALE)
> > -			writeb(cmd, info->reg.gpmc_nand_address);
> > -
> > +			reg = info->reg.gpmc_nand_address;
> >  		else /* NAND_NCE */
> > -			writeb(cmd, info->reg.gpmc_nand_data);
> > +			reg = info->reg.gpmc_nand_data;
> > +
> > +		if (info->nand.options & NAND_BUSWIDTH_16)
> > +			writew(cmd, reg);
> > +		else
> > +			writeb(cmd, reg);
> >  	}
> >  }
> >  
> > -- 
> > 1.7.8.6
> >

Patch

diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
index 5b31386..ae6738f 100644
--- a/drivers/mtd/nand/omap2.c
+++ b/drivers/mtd/nand/omap2.c
@@ -225,16 +225,20 @@  static void omap_hwcontrol(struct mtd_info *mtd, int cmd, unsigned int ctrl)
 {
 	struct omap_nand_info *info = container_of(mtd,
 					struct omap_nand_info, mtd);
+	void __iomem *reg;
 
 	if (cmd != NAND_CMD_NONE) {
 		if (ctrl & NAND_CLE)
-			writeb(cmd, info->reg.gpmc_nand_command);
-
+			reg = info->reg.gpmc_nand_command;
 		else if (ctrl & NAND_ALE)
-			writeb(cmd, info->reg.gpmc_nand_address);
-
+			reg = info->reg.gpmc_nand_address;
 		else /* NAND_NCE */
-			writeb(cmd, info->reg.gpmc_nand_data);
+			reg = info->reg.gpmc_nand_data;
+
+		if (info->nand.options & NAND_BUSWIDTH_16)
+			writew(cmd, reg);
+		else
+			writeb(cmd, reg);
 	}
 }