[U-Boot-Users] icache/dcache not working on PPC440

[U-Boot-Users] icache/dcache not working on PPC440

[Niklaus Giger]

Hi

Our HW engineers discovered that the U-Boot commands icache/dcache
do not work on PPC440x boards (at least yosemite and sequoia).

In my opinion icache/dcache work only on PPC40x processors where one
can alter the ICCR/DCCR registert. For the PPC440x register one should
tinker with the corresponding SA_I bit in the TLB.

Has somebody already solved this problem and would be willing to
share his patch?

If not I am willing to work on patch along the following lines:

a) add some C-callable routines to cpu/ppc4xx/start.S to use
the TLB Search Instruction and
b) to modify/setup a TLB from C
c) add in cpu/ppc4xx/cpu.c d/icache_dis/enable procedure
Any objections/comments?

Best regards

Niklaus Giger

[U-Boot-Users] icache/dcache not working on PPC440

[Stefan Roese]

Hi Niklaus,

On Friday 02 March 2007 16:51, Niklaus Giger wrote:
> Our HW engineers discovered that the U-Boot commands icache/dcache
> do not work on PPC440x boards (at least yosemite and sequoia).

Correct. On all 44x U-Boot platform cache in SDRAM is disabled right now. The 
main reason for this is the the 4xx EMAC driver needs it's buffer descriptors 
in uncached memory, or it must be changed to work with cached buffers too 
(invalidate & flush...).

> In my opinion icache/dcache work only on PPC40x processors where one
> can alter the ICCR/DCCR registert. For the PPC440x register one should
> tinker with the corresponding SA_I bit in the TLB.

Right.

> Has somebody already solved this problem and would be willing to
> share his patch?

From my point of view it doesn't make sense to support the icache/dcache 
commands for the 44x platforms. No real gain here. What makes real sense is 
to enable cache support in SDRAM. I have started working on an 440 port with 
caches enabled in SDRAM but other, more important stuff came in-between.

As mentioned above the main problem is the EMAC driver. It has either to be 
changed to support cache handling (invalidating/flushing) of the buffer 
descriptors. Or we must setup one small area in the SDRAM that is uncached 
and the driver uses this memory area for the buffer descriptors.

> If not I am willing to work on patch along the following lines:
>
> a) add some C-callable routines to cpu/ppc4xx/start.S to use
> the TLB Search Instruction and
> b) to modify/setup a TLB from C
> c) add in cpu/ppc4xx/cpu.c d/icache_dis/enable procedure
> Any objections/comments?

As mentioned above, I see no real gain here. If you really want to start on 
this issue, then please rework the EMAC driver as mentioned above and we can 
enable the caches in SDRAM. This would really bring a performance boost to 
the 44x platforms (image uncompressing, ECC generation, FPGA programming...).

But I have to admit the EMAC driver is total mess of #ifdef's (again)! :-(

Best regards,
Stefan

=====================================================================
DENX Software Engineering GmbH, HRB 165235 Munich, CEO: Wolfgang Denk
Office:  Kirchenstr. 5,       D-82194 Groebenzell,            Germany
=====================================================================

[U-Boot-Users] icache/dcache not working on PPC440

[Wolfgang Denk]

In message <200703021749.03000.sr@denx.de> you wrote:
> 
> As mentioned above the main problem is the EMAC driver. It has either to be 
> changed to support cache handling (invalidating/flushing) of the buffer 
> descriptors. Or we must setup one small area in the SDRAM that is uncached 
> and the driver uses this memory area for the buffer descriptors.

Other drivers may make similar assumptions. You will have  to  run  a
pretty  extensive  set of regression testing (including other network
drivers, USB, ...) when attempting to perform such a change.


Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH, HRB 165235 Munich, CEO: Wolfgang Denk
Office:  Kirchenstr. 5,       D-82194 Groebenzell,            Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
A Puritan is someone who is deathly afraid that  someone,  somewhere,
is having fun.

[U-Boot-Users] icache/dcache not working on PPC440

[Stefan Roese]

Hi Wolfgang,

On Friday 02 March 2007 17:54, Wolfgang Denk wrote:
> In message <200703021749.03000.sr@denx.de> you wrote:
> > As mentioned above the main problem is the EMAC driver. It has either to
> > be changed to support cache handling (invalidating/flushing) of the
> > buffer descriptors. Or we must setup one small area in the SDRAM that is
> > uncached and the driver uses this memory area for the buffer descriptors.
>
> Other drivers may make similar assumptions.

For 44x, I don't think so.

> You will have  to  run  a 
> pretty  extensive  set of regression testing (including other network
> drivers, USB, ...) when attempting to perform such a change.

Sure. This would be a major change and would need to be enabled in the board 
config file. And extensive testing of course.

Viele Gr??e,
Stefan

=====================================================================
DENX Software Engineering GmbH, HRB 165235 Munich, CEO: Wolfgang Denk
Office:  Kirchenstr. 5,       D-82194 Groebenzell,            Germany
=====================================================================

[U-Boot-Users] Understanding imw & inm

[Charles Krinke]

I have an 8541 board with a number of I2C chips and am having trouble understanding the use of inm & inw. I can iprobe, but when I try to write the first byte to zero, I get an error. The chip at address 70 is a Philips PCA9538 with four registers and I am trying to write the first register at offset zero to the value zero.
 
Can someone help me understand the error of my ways.
 
Charles
 
sff=> iprobe
Valid chip addresses: 2A 2D 37 57 58 59 68 70
sff=> help imd
imd chip address[.0, .1, .2] [# of objects]
    - i2c memory display
sff=> imd 70 0.1 4
0000: 7f 7f 7f 7f    ....
sff=> inm.b 70 0
00000000: 7f ? 0
Error writing the chip.
00000000: 7f ? .
sff=>

[U-Boot-Users] icache/dcache not working on PPC440

[Wolfgang Denk]

In message <es9h6q$2gp$1@sea.gmane.org> you wrote:
> 
> Our HW engineers discovered that the U-Boot commands icache/dcache
> do not work on PPC440x boards (at least yosemite and sequoia).

Please make sure to read the REAME and understand why you cannot
arbitrarily enable or disable caches in the system.

> Has somebody already solved this problem and would be willing to
> share his patch?

It's not a problem, it's a design issue.


Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH, HRB 165235 Munich, CEO: Wolfgang Denk
Office:  Kirchenstr. 5,       D-82194 Groebenzell,            Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
You are an excellent tactician, Captain. You let your second in  com-
mand attack while you sit and watch for weakness.
	-- Khan Noonian Singh, "Space Seed", stardate 3141.9