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Date:	Mon, 6 Oct 2014 19:15:53 -0500
From:	Scott Wood <scottwood@...escale.com>
To:	christophe leroy <christophe.leroy@....fr>
CC:	Mark Brown <broonie@...nel.org>, <linuxppc-dev@...ts.ozlabs.org>,
	<linux-kernel@...r.kernel.org>, <linux-spi@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] spi: fsl-spi: Fix parameter ram offset setup for
 CPM1

On Sat, 2014-10-04 at 14:02 +0200, christophe leroy wrote:
> Le 03/10/2014 22:29, Scott Wood a écrit :
> > On Fri, 2014-10-03 at 18:49 +0200, Christophe Leroy wrote:
> >> On CPM1, the SPI parameter RAM has a default location. In fsl_spi_cpm_get_pram()
> >> there was a confusion between the SPI_BASE register and the base of the SPI
> >> parameter RAM. Fortunatly, it was working properly with MPC866 and MPC885
> >> because they do set SPI_BASE, but on MPC860 and other old MPC8xx that doesn't
> >> set SPI_BASE, pram_ofs was not properly set. This patch fixes this confusion.
> >>
> >> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> >>
> >> ---
> >> Changes from v1 to v2: none
> >>
> >>   drivers/spi/spi-fsl-cpm.c | 9 ++++-----
> >>   1 file changed, 4 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/drivers/spi/spi-fsl-cpm.c b/drivers/spi/spi-fsl-cpm.c
> >> index 54b0637..0f3a912 100644
> >> --- a/drivers/spi/spi-fsl-cpm.c
> >> +++ b/drivers/spi/spi-fsl-cpm.c
> >> @@ -262,15 +262,14 @@ static unsigned long fsl_spi_cpm_get_pram(struct mpc8xxx_spi *mspi)
> >>   		pram_ofs = cpm_muram_alloc(SPI_PRAM_SIZE, 64);
> >>   		out_be16(spi_base, pram_ofs);
> >>   	} else {
> >> -		struct spi_pram __iomem *pram = spi_base;
> >> -		u16 rpbase = in_be16(&pram->rpbase);
> >> +		u16 rpbase = in_be16(spi_base);
> >>   
> >> -		/* Microcode relocation patch applied? */
> >> +		/* Microcode relocation patch applied | rpbase set by default */
> >>   		if (rpbase) {
> >>   			pram_ofs = rpbase;
> >>   		} else {
> >> -			pram_ofs = cpm_muram_alloc(SPI_PRAM_SIZE, 64);
> >> -			out_be16(spi_base, pram_ofs);
> >> +			pram_ofs = offsetof(cpm8xx_t, cp_dparam[PROFF_SPI]) -
> >> +				   offsetof(cpm8xx_t, cp_dpmem[0]);
> >>   		}
> >>   	}
> > Why is PROFF_SPI not coming from the device tree?
> That's where it starts to become tricky.
> 
> PROFF_SPI is defined in cpm1.h which is included by the driver already. 

Yes, but those values shouldn't be used.  It's a leftover from the old
way of hardcoding things and describing the hardware with kconfig rather
than the device tree.

> It provides the default offset from the start of the parameter RAM.
> Previously I had the following in my device tree, and the last part of 
> the source above (the one for rpbase == 0) could not work.
> 
>              spi: spi@a80 {
>                  cell-index = <0>;
>                  compatible = "fsl,spi", "fsl,cpm1-spi";
>                  reg = <0xa80 0x30 0x3d80 0x30>;
> 
> First reg area was the area for SPI registers. Second area was the 
> parameter RAM zone, which was just mapped to get access to the SPI_BASE 
> pointer (rpbase)
> 
> Now I have
> 
>                  compatible = "fsl,spi", "fsl,cpm1-spi-reloc";
>                  reg = <0xa80 0x30 0x3dac 0x2>;
> 
> First reg area is the area for SPI registers. Second area is the 
> SPI_BASE, as for the CPM2.
> 
> On recent 8xx (885 and 866 at least) it contains the offset (=0x1D80) of 
> the parameter RAM. But on old ones (860, ...) it contains 0. Therefore 
> we have to get the default index in another way.
> What I wanted was to keep something similar to what's done with CPM2.
> 
> What should it look like if that offset had to be in the device tree ?

If the offset is not relocatable or discoverable, it should stay in the
device tree.  If you have an old chip you wouldn't have
fsl,cpm1-spi-reloc and thus you'd still have "0x3d80 0x30" in reg.

> > Why don't I see any
> > cpm spi in any device tree nor any binding for it?
> There's one in mgcoge.dts:
> 
>              spi@...a0 {
>                  cell-index = <0>;
>                  compatible = "fsl,spi", "fsl,cpm2-spi";
>                  reg = <0x11a80 0x40 0x89fc 0x2>;

I'm not sure why I missed that, but this patch is for cpm1-spi, not
cpm2-spi...

Even if you insist on keeping your board dts out-of-tree, there should
at least be a binding in-tree.

BTW, more specific compatibles should come first.

-Scott


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