linux-kernel - Re: [PATCH v5 2/2] mtd: rawnand: Add NAND controller support on Intel LGM SoC

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Message-ID: <20200507082730.6425cd96@collabora.com>
Date:   Thu, 7 May 2020 08:27:30 +0200
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     "Ramuthevar, Vadivel MuruganX" 
        <vadivel.muruganx.ramuthevar@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
        devicetree@...r.kernel.org, miquel.raynal@...tlin.com,
        richard@....at, vigneshr@...com, arnd@...db.de,
        brendanhiggins@...gle.com, tglx@...utronix.de,
        anders.roxell@...aro.org, masonccyang@...c.com.tw,
        robh+dt@...nel.org, linux-mips@...r.kernel.org,
        hauke.mehrtens@...el.com, andriy.shevchenko@...el.com,
        qi-ming.wu@...el.com, cheol.yong.kim@...el.com
Subject: Re: [PATCH v5 2/2] mtd: rawnand: Add NAND controller support on
 Intel LGM SoC

On Thu, 7 May 2020 14:13:42 +0800
"Ramuthevar, Vadivel MuruganX"
<vadivel.muruganx.ramuthevar@...ux.intel.com> wrote:

> Hi Boris,
> 
>     Thank you very much for the review comments and your time...
> 
> On 7/5/2020 1:28 pm, Boris Brezillon wrote:
> > On Thu,  7 May 2020 08:15:37 +0800
> > "Ramuthevar,Vadivel MuruganX"
> > <vadivel.muruganx.ramuthevar@...ux.intel.com> wrote:
> >   
> >> +	reg = readl(ebu_host->ebu + EBU_ADDR_SEL(ebu_host->cs_num));
> >> +	writel(reg | EBU_ADDR_MASK(5) | EBU_ADDR_SEL_REGEN,
> >> +	       ebu_host->ebu + EBU_ADDR_SEL(ebu_host->cs_num));  
> > 
> > Seriously, did you really think I would not notice what you're doing
> > here?  
> Yes , I know that you have very good understanding about this.
>   You're reading the previous value which either contains a default
> > mapping or has the mapping set by the bootloader, and write it back to
> > the register along with a new mask and the REGEN bit set (which
> > BTW is wrong since you don't mask out other fields before updating
> > them).  
> There is no other field get overwritten
>   This confirms that this Core -> FPI address translation exists
> > and has to be set properly, so please stop lying about that.  
> 
> Sorry, there is no SW translation, as I have mentioned that it's 
> optional only, for safer side , reading and writing the default values.

Then write EBU_ADDR_SEL_REGEN and we'll if see that works. I suspect it
won't.

> The memory region to enabled that's my concern so written the same 
> register values.

I don't buy that, sorry.

> 
> This will not be impact other fields, so please see below for reference
> 
> The EBU Address Select Registers EBU_ADDR_SEL_0 to EBU_ADDSEL3 establish 
> and control memory regions for external accesses.
> 
> Reset Value: 17400001H

See, as suspected the reset value is exactly what you expect.