linux-kernel - Re: [PATCH v8 2/4] misc: Generic on-chip SRAM allocation driver

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Date:	Mon, 11 Feb 2013 19:15:24 +0100
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Shawn Guo <shawn.guo@...aro.org>,
	Richard Zhao <richard.zhao@...escale.com>,
	Huang Shijie <shijie8@...il.com>,
	Dong Aisheng <dong.aisheng@...aro.org>,
	Matt Porter <mporter@...com>,
	Fabio Estevam <fabio.estevam@...escale.com>,
	Javier Martin <javier.martin@...ta-silicon.com>,
	kernel@...gutronix.de, devicetree-discuss@...ts.ozlabs.org
Subject: Re: [PATCH v8 2/4] misc: Generic on-chip SRAM allocation driver

Hi Grant,

Am Freitag, den 08.02.2013, 20:16 +0000 schrieb Grant Likely:
> On Mon,  4 Feb 2013 12:32:16 +0100, Philipp Zabel <p.zabel@...gutronix.de> wrote:
> > This driver requests and remaps a memory region as configured in the
> > device tree. It serves memory from this region via the genalloc API.
> > It optionally enables the SRAM clock.
> > 
> > Other drivers can retrieve the genalloc pool from a phandle pointing
> > to this drivers' device node in the device tree.
> > 
> > The allocation granularity is hard-coded to 32 bytes for now,
> > to make the SRAM driver useful for the 6502 remoteproc driver.
> > There is overhead for bigger SRAMs, where only a much coarser
> > allocation granularity is needed: At 32 bytes minimum allocation
> > size, a 256 KiB SRAM needs a 1 KiB bitmap to track allocations.
> > 
> > Signed-off-by: Philipp Zabel <p.zabel@...gutronix.de>
> > Reviewed-by: Shawn Guo <shawn.guo@...aro.org>
> > ---
> > Changes since v7:
> >  - Removed obsolete __devinit/__devexit/__devexit_p
> > ---
> >  Documentation/devicetree/bindings/misc/sram.txt |   17 ++++
> >  drivers/misc/Kconfig                            |    9 ++
> >  drivers/misc/Makefile                           |    1 +
> >  drivers/misc/sram.c                             |  121 +++++++++++++++++++++++
> >  4 files changed, 148 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/misc/sram.txt
> >  create mode 100644 drivers/misc/sram.c
> > 
> > diff --git a/Documentation/devicetree/bindings/misc/sram.txt b/Documentation/devicetree/bindings/misc/sram.txt
> > new file mode 100644
> > index 0000000..b64136c
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/misc/sram.txt
> > @@ -0,0 +1,17 @@
> > +Generic on-chip SRAM
> > +
> > +Simple IO memory regions to be managed by the genalloc API.
> > +
> > +Required properties:
> > +
> > +- compatible : sram
> 
> I'm a little concerned that 'sram' is just too generic for a compatible
> value and we may end up needing a blacklist of systems where the sram
> device should not be driven with this driver. If you can think of
> a more descriptive name here then I would use it.

various SoC vendors call this (variations of) "on-chip" or "internal"
SRAM/memory. "on-chip-sram" or "internal-sram" are still plenty generic,
though. How about "mmio-sram", as opposed to an SRAM that needs more
than the simple mmio region handled by this driver?

An alternative would be to use the vendor specific names and grow a
compatible list in the driver ("fsl,ocram", "ti,ocm", ...).

> However, I'm not worried about it enough to nak it and the rest of the
> series looks fine.
> 
> Acked-by: Grant Likely <grant.likely@...retlab.ca>

Thank you.

regards
Philipp

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