linux-kernel - Re: [PATCH v3 2/4] mtd: rawnand: Add Macronix MX25F0A NAND controller

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Message-ID: <OF9EFE4BDE.3166D82B-ON4825841E.00307F51-4825841E.00310FB5@mxic.com.tw>
Date:   Wed, 19 Jun 2019 16:55:52 +0800
From:   masonccyang@...c.com.tw
To:     "Boris Brezillon" <boris.brezillon@...labora.com>
Cc:     bbrezillon@...nel.org, broonie@...nel.org,
        christophe.kerello@...com, computersforpeace@...il.com,
        devicetree@...r.kernel.org, dwmw2@...radead.org,
        geert@...ux-m68k.org, juliensu@...c.com.tw, lee.jones@...aro.org,
        liang.yang@...ogic.com, linux-kernel@...r.kernel.org,
        linux-mtd@...ts.infradead.org, linux-spi@...r.kernel.org,
        marcel.ziswiler@...adex.com, marek.vasut@...il.com,
        mark.rutland@....com, "Miquel Raynal" <miquel.raynal@...tlin.com>,
        paul.burton@...s.com, richard@....at, robh+dt@...nel.org,
        stefan@...er.ch, zhengxunli@...c.com.tw
Subject: Re: [PATCH v3 2/4] mtd: rawnand: Add Macronix MX25F0A NAND controller


Hi Boris,

> > > 
> > > Re: [PATCH v3 2/4] mtd: rawnand: Add Macronix MX25F0A NAND 
controller
> > > 
> > > On Tue, 18 Jun 2019 08:14:36 +0200
> > > Boris Brezillon <boris.brezillon@...labora.com> wrote:
> > > 
> > > > > > > > > 
> > > > > > > > > How to make all #CS keep high for NAND to enter 
> > > > > > > > > low-power standby mode if driver don't use 
> > "legacy.select_chip()" 
> > > > > ? 
> > > > > > > > 
> > > > > > > > See commit 02b4a52604a4 ("mtd: rawnand: Make 
->select_chip() 
> > > > > optional 
> > > > > > > > when ->exec_op() is implemented") which states:
> > > > > > > > 
> > > > > > > >         "When [->select_chip() is] not implemented, the 
core 
> > is 
> > > > > assuming 
> > > > > > > >    the CS line is automatically asserted/deasserted by the 
 
> > driver 
> > > > > > > >    ->exec_op() implementation." 
> > > > > > > > 
> > > > > > > > Of course, the above is right only when the controller 
driver 
> > 
> > > > > supports 
> > > > > > > > the ->exec_op() interface. 
> > > > > > > 
> > > > > > > Currently, it seems that we will get the incorrect data and  

> > error
> > > > > > > operation due to CS in error toggling if CS line is 
controlled 
> > in 
> > > > > > > ->exec_op(). 
> > > 
> > > Oh, and please provide the modifications you added on top of this 
patch.
> > > Right now we're speculating on what you've done which is definitely 
not
> > > an efficient way to debug this sort of issues. 
> > 
> > The patch is to add in beginning of ->exec_op() to control CS# low and 

> > before return from ->exec_op() to control CS# High.
> > i.e,.
> > static in mxic_nand_exec_op( )
> > {
> >  cs_to_low();
> > 
> > 
> > 
> >  cs_to_high();
> >  return;
> > }
> > 
> > But for nand_onfi_detect(), 
> > it calls nand_read_param_page_op() and then nand_read_data_op().
> > mxic_nand_exec_op() be called twice for nand_onfi_detect() and
> > driver will get incorrect ONFI parameter table data from 
> > nand_read_data_op().
> 
> And I think it's valid to release the CE pin between
> read_param_page_op() (CMD(0xEC)+ADDR(0x0)) and read_data_op() (data
> cycles) if your chip is CE-dont-care compliant. So, either you have a
> problem with your controller driver (CS-related timings are incorrect)
> or your chip is not CE-dont-care compliant.

Understood, I will try to fix it on my NFC driver.

And I think CS# pin goes to high is much important for power consumption.

thanks & best regards,
Mason





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