linux-kernel - Re: [LINUX PATCH v14] mtd: rawnand: pl353: Add basic driver for arm pl353 smc nand interface

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Date:   Thu, 25 Apr 2019 13:23:37 +0200
From:   Helmut Grohne <helmut.grohne@...enta.de>
To:     Naga Sureshkumar Relli <nagasure@...inx.com>
CC:     "bbrezillon@...nel.org" <bbrezillon@...nel.org>,
        "miquel.raynal@...tlin.com" <miquel.raynal@...tlin.com>,
        "richard@....at" <richard@....at>,
        "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "computersforpeace@...il.com" <computersforpeace@...il.com>,
        "marek.vasut@...il.com" <marek.vasut@...il.com>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michal Simek <michals@...inx.com>,
        "nagasureshkumarrelli@...il.com" <nagasureshkumarrelli@...il.com>
Subject: Re: [LINUX PATCH v14] mtd: rawnand: pl353: Add basic driver for arm
 pl353 smc nand interface

On Wed, Apr 24, 2019 at 05:04:38AM +0000, Naga Sureshkumar Relli wrote:
> > You previously used cond_resched (via nand_wait_ready) here. Why did you change it to
> > cpu_relax()?
> I just replicated the pl353_wait_for_ecc_done() API definition.
> But did you see any issue with this?
> Anyway I will replace it with cond_resched(), instead of cpu_releax()

This was an observation and it made me ask for reasons. I did not have
any practical issues here.

> Did you follow the same thing that you tried earlier?
> i.e. updated "nand-bus-width" property and "nand-ecc-mode" ?

Yes, I used the same device tree that made v13 partially work here.

> > After trying the driver, the flash chip was bricked. Neither the old driver nor the uboot-xlnx
> > driver nor the Xilinx fsbl are able to talk to the chip afterwards. This behaviour persists even
> > after a full power cycle. I'll try reinitializing the flash chip next. I've only seen this behaviour
> > once, so there is a slight chance that the cause is something else.
> Sometimes I also faced the same problem during driver development.
> What I did is, in standalone nandps driver example,  I forcibly created BBT in the init and once
>  it is done. I just reloaded the actual example. Then after wards u-boot and Linux are able to scan
> the BBT.

I confirm. It was just the BBT being bad. It can also be recreated using
u-boot with "nand scrib.chip".

I also spent some time reviewing the code and will send another mail
about that.

Helmut