[PATCH] [V2] powerpc: legacy_serial: reg-offset & shift aren't used

[PATCH] [V2] powerpc: legacy_serial: reg-offset & shift aren't used

[John Linn]

The legacy serial driver does not work with an 8250
type UART that uses reg-offset and reg-shift. This
change updates the driver so it doesn't find the UART
when those properties are present on the UART in the
device tree for soc devices.

Signed-off-by: John Linn <john.linn@xilinx.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
---
V2

Corrected logic to use "||" rather than "&&".

 arch/powerpc/kernel/legacy_serial.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/kernel/legacy_serial.c b/arch/powerpc/kernel/legacy_serial.c
index 61dd174..cf37f5c 100644
--- a/arch/powerpc/kernel/legacy_serial.c
+++ b/arch/powerpc/kernel/legacy_serial.c
@@ -136,6 +136,11 @@ static int __init add_legacy_soc_port(struct device_node *np,
 	if (of_get_property(np, "clock-frequency", NULL) == NULL)
 		return -1;
 
+	/* if reg-shift or offset, don't try to use it */
+	if ((of_get_property(np, "reg-shift", NULL) != NULL) ||
+		(of_get_property(np, "reg-offset", NULL) != NULL))
+		return -1;
+
 	/* if rtas uses this device, don't try to use it as well */
 	if (of_get_property(np, "used-by-rtas", NULL) != NULL)
 		return -1;
-- 
1.5.2.1



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Re: [PATCH] [V2] powerpc: legacy_serial: reg-offset & shift aren't used

[Benjamin Herrenschmidt]

On Tue, 2008-07-01 at 10:52 -0700, John Linn wrote:
> The legacy serial driver does not work with an 8250
> type UART that uses reg-offset and reg-shift. This
> change updates the driver so it doesn't find the UART
> when those properties are present on the UART in the
> device tree for soc devices.
> 
> Signed-off-by: John Linn <john.linn@xilinx.com>
> Acked-by: Grant Likely <grant.likely@secretlab.ca>
> ---
> V2
> 
> Corrected logic to use "||" rather than "&&".

I have some problems with this patch:

 - First if the properties are present but their value match the
register layout of a standard UART, we will bail out... not nice.

 - Why don't we just implement support for the reg-shift and
offset instead ?

Cheers,
Ben.

>  arch/powerpc/kernel/legacy_serial.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/legacy_serial.c b/arch/powerpc/kernel/legacy_serial.c
> index 61dd174..cf37f5c 100644
> --- a/arch/powerpc/kernel/legacy_serial.c
> +++ b/arch/powerpc/kernel/legacy_serial.c
> @@ -136,6 +136,11 @@ static int __init add_legacy_soc_port(struct device_node *np,
>  	if (of_get_property(np, "clock-frequency", NULL) == NULL)
>  		return -1;
>  
> +	/* if reg-shift or offset, don't try to use it */
> +	if ((of_get_property(np, "reg-shift", NULL) != NULL) ||
> +		(of_get_property(np, "reg-offset", NULL) != NULL))
> +		return -1;
> +
>  	/* if rtas uses this device, don't try to use it as well */
>  	if (of_get_property(np, "used-by-rtas", NULL) != NULL)
>  		return -1;

Re: [PATCH] [V2] powerpc: legacy_serial: reg-offset & shift aren't used

[Josh Boyer]

On Mon, 07 Jul 2008 16:47:08 +1000
Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:

> On Tue, 2008-07-01 at 10:52 -0700, John Linn wrote:
> > The legacy serial driver does not work with an 8250
> > type UART that uses reg-offset and reg-shift. This
> > change updates the driver so it doesn't find the UART
> > when those properties are present on the UART in the
> > device tree for soc devices.
> > 
> > Signed-off-by: John Linn <john.linn@xilinx.com>
> > Acked-by: Grant Likely <grant.likely@secretlab.ca>
> > ---
> > V2
> > 
> > Corrected logic to use "||" rather than "&&".
> 
> I have some problems with this patch:
> 
>  - First if the properties are present but their value match the
> register layout of a standard UART, we will bail out... not nice.

Why would they be present in that case?

>  - Why don't we just implement support for the reg-shift and
> offset instead ?

Probably because the last time someone suggested that it spawned a
lengthy debate about what reg-offset/shift were supposed to do.

josh

Re: [PATCH] [V2] powerpc: legacy_serial: reg-offset & shift aren't used

[Grant Likely]

On Mon, Jul 7, 2008 at 12:47 AM, Benjamin Herrenschmidt
<benh@kernel.crashing.org> wrote:
> On Tue, 2008-07-01 at 10:52 -0700, John Linn wrote:
>> The legacy serial driver does not work with an 8250
>> type UART that uses reg-offset and reg-shift. This
>> change updates the driver so it doesn't find the UART
>> when those properties are present on the UART in the
>> device tree for soc devices.
>
> I have some problems with this patch:
>
>  - First if the properties are present but their value match the
> register layout of a standard UART, we will bail out... not nice.

Okay, that can be fixed.

>  - Why don't we just implement support for the reg-shift and
> offset instead ?

We can do this, but this patch was simpler for solving the immediate
problem in .26

g.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.

Re: [PATCH] [V2] powerpc: legacy_serial: reg-offset & shift aren't used

[Benjamin Herrenschmidt]

> >  - First if the properties are present but their value match the
> > register layout of a standard UART, we will bail out... not nice.
> 
> Why would they be present in that case?

Why not ?

> >  - Why don't we just implement support for the reg-shift and
> > offset instead ?
> 
> Probably because the last time someone suggested that it spawned a
> lengthy debate about what reg-offset/shift were supposed to do.

That's lame, their definition is already quite there.

Ben.