[PATCH] mpc52xx_psc_spi setting the tdfOnExit flag only on the last byte

[PATCH] mpc52xx_psc_spi setting the tdfOnExit flag only on the last byte

[Stefano Babic]

According to the manual the "tdfOnExit" flag must be set on the last byte
we want to send. The PSC controller holds SS low until the flag is set.
However, the flag was set always on the last byte of the FIFO, independently if
it is the last byte of the transfer. This generates spurious toggling of the
SS signals that breaks the protocol of some peripherals.

Signed-off-by: Stefano Babic <sbabic-ynQEQJNshbs@public.gmane.org>



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[PATCH] mpc52xx_psc_spi setting the tdfOnExit flag only on the last byte

[Stefano Babic]

Signed-off-by: Stefano Babic <sbabic-ynQEQJNshbs@public.gmane.org>
---
 drivers/spi/mpc52xx_psc_spi.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/mpc52xx_psc_spi.c b/drivers/spi/mpc52xx_psc_spi.c
index 41f9921..d7b1fb5 100644
--- a/drivers/spi/mpc52xx_psc_spi.c
+++ b/drivers/spi/mpc52xx_psc_spi.c
@@ -149,6 +148,7 @@ static int mpc52xx_psc_spi_transfer_rxtx(struct spi_device *spi,
 	unsigned rfalarm;
 	unsigned send_at_once = MPC52xx_PSC_BUFSIZE;
 	unsigned recv_at_once;
+	int last_block = 0;
 
 	if (!t->tx_buf && !t->rx_buf && t->len)
 		return -EINVAL;
@@ -158,15 +158,17 @@ static int mpc52xx_psc_spi_transfer_rxtx(struct spi_device *spi,
 	while (rb < t->len) {
 		if (t->len - rb > MPC52xx_PSC_BUFSIZE) {
 			rfalarm = MPC52xx_PSC_RFALARM;
+			last_block = 0;
 		} else {
 			send_at_once = t->len - sb;
 			rfalarm = MPC52xx_PSC_BUFSIZE - (t->len - rb);
+			last_block = 1;
 		}
 
 		dev_dbg(&spi->dev, "send %d bytes...\n", send_at_once);
 		for (; send_at_once; sb++, send_at_once--) {
 			/* set EOF flag before the last word is sent */
-			if (send_at_once == 1)
+			if (send_at_once == 1 && last_block)
 				out_8(&psc->ircr2, 0x01);
 
 			if (tx_buf)
-- 
1.5.4.3


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Re: [PATCH] mpc52xx_psc_spi setting the tdfOnExit flag only on the last byte

[Grant Likely]

On Tue, Sep 30, 2008 at 11:22:52AM +0200, Stefano Babic wrote:
> Signed-off-by: Stefano Babic <sbabic-ynQEQJNshbs@public.gmane.org>
> ---
>  drivers/spi/mpc52xx_psc_spi.c |    6 ++++--
>  1 files changed, 4 insertions(+), 2 deletions(-)

Other than the issue of the missing description, this looks right to me.

Acked-by: Grant Likely <grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>

> 
> diff --git a/drivers/spi/mpc52xx_psc_spi.c b/drivers/spi/mpc52xx_psc_spi.c
> index 41f9921..d7b1fb5 100644
> --- a/drivers/spi/mpc52xx_psc_spi.c
> +++ b/drivers/spi/mpc52xx_psc_spi.c
> @@ -149,6 +148,7 @@ static int mpc52xx_psc_spi_transfer_rxtx(struct spi_device *spi,
>  	unsigned rfalarm;
>  	unsigned send_at_once = MPC52xx_PSC_BUFSIZE;
>  	unsigned recv_at_once;
> +	int last_block = 0;
>  
>  	if (!t->tx_buf && !t->rx_buf && t->len)
>  		return -EINVAL;
> @@ -158,15 +158,17 @@ static int mpc52xx_psc_spi_transfer_rxtx(struct spi_device *spi,
>  	while (rb < t->len) {
>  		if (t->len - rb > MPC52xx_PSC_BUFSIZE) {
>  			rfalarm = MPC52xx_PSC_RFALARM;
> +			last_block = 0;
>  		} else {
>  			send_at_once = t->len - sb;
>  			rfalarm = MPC52xx_PSC_BUFSIZE - (t->len - rb);
> +			last_block = 1;
>  		}
>  
>  		dev_dbg(&spi->dev, "send %d bytes...\n", send_at_once);
>  		for (; send_at_once; sb++, send_at_once--) {
>  			/* set EOF flag before the last word is sent */
> -			if (send_at_once == 1)
> +			if (send_at_once == 1 && last_block)
>  				out_8(&psc->ircr2, 0x01);
>  
>  			if (tx_buf)
> -- 
> 1.5.4.3
> 
> 
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Re: [PATCH] mpc52xx_psc_spi setting the tdfOnExit flag only on the last byte

[Grant Likely]

On Tue, Sep 30, 2008 at 11:22:51AM +0200, Stefano Babic wrote:
> According to the manual the "tdfOnExit" flag must be set on the last byte
> we want to send. The PSC controller holds SS low until the flag is set.
> However, the flag was set always on the last byte of the FIFO, independently if
> it is the last byte of the transfer. This generates spurious toggling of the
> SS signals that breaks the protocol of some peripherals.
> 
> Signed-off-by: Stefano Babic <sbabic-ynQEQJNshbs@public.gmane.org>

Your patchs and descriptions are getting sent in separate emails.  How are you
sending your patches?

g.


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Re: [PATCH] mpc52xx_psc_spi setting the tdfOnExit flag only on the last byte

[Stefano Babic]

Grant Likely wrote:
> Your patchs and descriptions are getting sent in separate emails.  How are you
> sending your patches?

I know, I have not found a way how to tell git-send-email to send
everything in one e-mail:

git-send-email --to spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org --compose
--subject  "[PATCH] mpc52xx_psc_spi setting the tdfOnExit flag only on
the last byte" 001-According-to-the-manual.patch

Probably it is very easy, but I have not found the right way ;)

Stefano

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Re: [PATCH] mpc52xx_psc_spi setting the tdfOnExit flag only on the last byte

[Grant Likely]

On Tue, Sep 30, 2008 at 8:15 AM, Stefano Babic <sbabic-ynQEQJNshbs@public.gmane.org> wrote:
> Grant Likely wrote:
>> Your patchs and descriptions are getting sent in separate emails.  How are you
>> sending your patches?
>
> I know, I have not found a way how to tell git-send-email to send
> everything in one e-mail:
>
> git-send-email --to spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org --compose
> --subject  "[PATCH] mpc52xx_psc_spi setting the tdfOnExit flag only on
> the last byte" 001-According-to-the-manual.patch
>
> Probably it is very easy, but I have not found the right way ;)

You need to provide the patch description when you commit the change,
not when you send the email.

While you cannot edit a commit directly (commits are immutable), you
can create a new commit from the old using git-cherry-pick:

$ man git-cherry-pick
$ git branch old                 # Save the current location
$ git reset --hard old~1         # reset to just before the commit to edit
$ git-cherry-pick -e old         # Cherry pick the commit that you
                                 # want and edit the commit log.

g.

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Re: [PATCH] mpc52xx_psc_spi setting the tdfOnExit flag only on the last byte

[Stefan Roese]

On Tuesday 30 September 2008, Stefano Babic wrote:
> I know, I have not found a way how to tell git-send-email to send
> everything in one e-mail:
>
> git-send-email --to spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org --compose
> --subject  "[PATCH] mpc52xx_psc_spi setting the tdfOnExit flag only on
> the last byte" 001-According-to-the-manual.patch
>
> Probably it is very easy, but I have not found the right way ;)

I generate the patch with "git format-patch -1 -o directory" and then send it 
with "git send-email --to list directory/patch".

Best regards,
Stefan

=====================================================================
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-0 Fax: +49-8142-66989-80  Email: office-ynQEQJNshbs@public.gmane.org
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Re: [PATCH] mpc52xx_psc_spi setting the tdfOnExit flag only on the last byte

[Stefano Babic]

Grant Likely wrote:
> $ man git-cherry-pick
> $ git branch old                 # Save the current location
> $ git reset --hard old~1         # reset to just before the commit to edit
> $ git-cherry-pick -e old         # Cherry pick the commit that you

Stefan Roese wrote:
> I generate the patch with "git format-patch -1 -o directory" and then send it 
> with "git send-email --to list directory/patch".

Thanks a lot both ! I did not know how to use git-cherry-pick, I have
learned now. By the way, the mistake was trivial (but I have not seen) :
I forgot to add an empty line between subject and text when I commit the
changes and git-send-email took everything as subject ;)

Stefano

-- 
=====================================================================
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-0 Fax: +49-8142-66989-80  Email: office-ynQEQJNshbs@public.gmane.org
=====================================================================


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