Date:   Tue, 25 Oct 2016 05:02:47 +0000
From:   Punnaiah Choudary Kalluri <punnaiah.choudary.kalluri@...inx.com>
To:     Jason Gunthorpe <jgunthorpe@...idianresearch.com>
CC:     Boris Brezillon <boris.brezillon@...e-electrons.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "michal.simek@...inx.com" <michal.simek@...inx.com>,
        "ezequiel.garcia@...e-electrons.com" 
        <ezequiel.garcia@...e-electrons.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "rob@...dley.net" <rob@...dley.net>,
        "galak@...eaurora.org" <galak@...eaurora.org>,
        "computersforpeace@...il.com" <computersforpeace@...il.com>,
        "dwmw2@...radead.org" <dwmw2@...radead.org>
Subject: RE: [v7, 1/3] nand: pl353: Add basic driver for arm pl353 smc nand
 interface



> -----Original Message-----
> From: Jason Gunthorpe [mailto:jgunthorpe@...idianresearch.com]
> Sent: Tuesday, October 25, 2016 10:16 AM
> To: Punnaiah Choudary Kalluri <punnaia@...inx.com>
> Cc: Boris Brezillon <boris.brezillon@...e-electrons.com>;
> mark.rutland@....com; linux-mtd@...ts.infradead.org;
> michal.simek@...inx.com; ezequiel.garcia@...e-electrons.com; linux-
> kernel@...r.kernel.org; rob@...dley.net; galak@...eaurora.org;
> computersforpeace@...il.com; dwmw2@...radead.org
> Subject: Re: [v7, 1/3] nand: pl353: Add basic driver for arm pl353 smc nand
> interface
>
> On Tue, Oct 25, 2016 at 03:58:49AM +0000, Punnaiah Choudary Kalluri wrote:
>
> > > I have hacked the v7 patchset enough to work on 4.8 and hacked it some
> > > more to work on my hardware. The driver appears to be in no better
> > > shape than the 3.12 out-of-tree Xilinx release I was using previously..
> >
> > The driver in Xilinx tree works with 4.6 kernel and adopted the
> > required
>
> I mean, the driver from the 3.12 Xilinx tree that I last looked
> at years ago. This is at v7 now and is still needs lots of work, I did
> some fixing, including making parts of it work on 4.8.
> You can copy it out of the patch I sent you.
>
> > Changes (may release in 1-2 weeks). Still it need some rework, now a days
> > I am seeing many requests from different people for this driver and some
> of
> > Them are using different version of IP as you know this IP has four variants
> and
> > Xilinx is using the pl353 variant.
>
> Well, I am using Xilinx Zynq hardware and care about making that
> configuration actually work. This is the last driver I require to use
> Zynq with mainline.
>

Sure.

> It clearly needs more work than just forward porting to 4.8, so please
> let me know if you are able to tackle this.

I didn't say that I am forwarding the patch working with 4.8. I said
We made changes to driver compatible for 4.6 and working on driver rework,
Most of your comments also part of that.

>
> > Let's wait for the next series of patches and Get the patches tested
> > with others as well along with the review comments.
>
> You now have 10 review comments from me, please respond to all of them
> in
> your v8 patchset - no sense in continuing to drag this out.
>

See above.

> Please cc me on future series.

Ok.

Regards,
Punnaiah

>
> Jason
>
> > Regards,
> > Punnaiah
> > > I've attached the ugly, ugly patch I made, it may save you some time
> > > when preparing v8.
> > >
> > > Commentary:
> > >  1) nand_chip already includes mtd_info, no reason for a second one in
> > >     the pl353_nand_info struct. The standard accessors mtd_to_nand/etc
> > >     should be used instead of priv
> > >  2) I hacked out all the ECC stuff from the driver since I don't use
> > >     it and it was broken.. Obviously some has to come back, but fixing
> > >     other things on this list first will make that much easier and better..
> > >  3) pl353_nand_write_page_swecc/pl353_nand_read_page_swecc are
> pure
> > >     outdated copies of the core routines and should not exist in a
> > >     driver. This needs to be fixed so nand_scan_tail sets them.
> > >     This seems to be a side effect of #9 ?
> > >  4) The hacky stuff to detect 2 vs 3 address cycle NAND doesn't work,
> > >     and doesn't work without ONFI (see patch for possible fix). The
> > >     driver should probably use the same scheme the core code uses..
> > >     But this is all a problem because of #10
> > >  5) The driver assumes alignment of the iomap, needs to use + not |
> > >     when constructing the address. (yes, this blows up on my system)
> > >  6) Driver unconditionally sets timing to ONFI mode 0 (slow!)
> > >     Maybe timing should be common code driven by DT..
> > >  7) Driver unconditionally selects a BBT format, and an ECC layout
> > >     (neither match what my system uses, but I guess that is a core mtd
> > >     issue these days :/)
> > >  8) Driver unconditionally forces a chip-delay (wrong for my
> > >     system) maybe this should be common code driven by DT..
> > >  9) This buisness with pl353_nand_ecc_init and the
> > >     special functions to do PL353_NAND_LAST_TRANSFER_LENGTH stuff
> > >     is just horrid. I'd expect that is a big NAK.
> > >
> > >     The driver needs to implement read_buf *properly* so the core
> > >     routines can be used instead of trying to 'fix' the call sites
> > >     to do the PL353_NAND_LAST_TRANSFER_LENGTH stuff.
> > >  10) pl353_nand_cmd_function is a wonky copy of nand_command_lp,
> > > maybe
> > >      this driver should use cmd_ctrl, or the core code should be
> > >      refactored some more..


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