linux-kernel - Re: [PATCH] mtd: rawnand: Do not check for bad block if bbt is unavailable

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Message-ID: <20210204100408.6eb053d8@xps13>
Date:   Thu, 4 Feb 2021 10:04:08 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Boris Brezillon <boris.brezillon@...labora.com>
Cc:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        richard@....at, vigneshr@...com, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        bjorn.andersson@...aro.org
Subject: Re: [PATCH] mtd: rawnand: Do not check for bad block if bbt is
 unavailable

Hi Boris,

Boris Brezillon <boris.brezillon@...labora.com> wrote on Thu, 4 Feb
2021 09:59:45 +0100:

> On Thu, 4 Feb 2021 14:22:21 +0530
> Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org> wrote:
> 
> > On Thu, Feb 04, 2021 at 09:13:36AM +0100, Miquel Raynal wrote:  
> > > Hi Manivannan,
> > > 
> > > Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org> wrote on Wed,
> > > 03 Feb 2021 17:11:31 +0530:
> > >     
> > > > On 3 February 2021 4:54:22 PM IST, Boris Brezillon <boris.brezillon@...labora.com> wrote:    
> > > > >On Wed, 03 Feb 2021 16:22:42 +0530
> > > > >Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org> wrote:
> > > > >      
> > > > >> On 3 February 2021 3:49:14 PM IST, Boris Brezillon      
> > > > ><boris.brezillon@...labora.com> wrote:      
> > > > >> >On Wed, 03 Feb 2021 15:42:02 +0530
> > > > >> >Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org> wrote:
> > > > >> >        
> > > > >> >> >> 
> > > > >> >> >> I got more information from the vendor, Telit. The access to      
> > > > >the        
> > > > >> >3rd          
> > > > >> >> >partition is protected by Trustzone and any access in non      
> > > > >privileged      
> > > > >> >> >mode (where Linux kernel runs) causes kernel panic and the device
> > > > >> >> >reboots.         
> > > > >> >
> > > > >> >Out of curiosity, is it a per-CS-line thing or is this section
> > > > >> >protected on all CS?
> > > > >> >        
> > > > >> 
> > > > >> Sorry, I didn't get your question.       
> > > > >
> > > > >The qcom controller can handle several chips, each connected through a
> > > > >different CS (chip-select) line, right? I'm wondering if the firmware
> > > > >running in secure mode has the ability to block access for a specific
> > > > >CS line or if all CS lines have the same constraint. That will impact
> > > > >the way you describe it in your DT (in one case the secure-region
> > > > >property should be under the controller node, in the other case it
> > > > >should be under the NAND chip node).      
> > > > 
> > > > Right. I believe the implementation is common to all NAND chips so the property should be in the controller node.     
> > > 
> > > Looks weird: do you mean that each of the chips will have a secure area?    
> > 
> > I way I said is, the "secure-region" property will be present in the controller
> > node and not in the NAND chip node since this is not related to the device
> > functionality.
> > 
> > But for referencing the NAND device, the property can have the phandle as below:
> > 
> > secure-region = <&nand0 0xffff>;  
> 
> My question was really what happens from a functional PoV. If you have
> per-chip protection at the FW level, this property should be under the
> NAND node. OTH, if the FW doesn't look at the selected chip before
> blocking the access, it should be at the controller level. So, you
> really have to understand what the secure FW does.

I'm not so sure actually, that's why I like the phandle to nand0 -> in
any case it's not a property of the NAND chip itself, it's kind of a
host constraint, so I don't get why the property should be at the
NAND node level?

Also, we should probably support several secure regions (which could be
a way to express the fact that the FW does not look at the CS)?