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To:     "Boris Brezillon" <boris.brezillon@collabora.com>
Cc:     bbrezillon@kernel.org, broonie@kernel.org,
        christophe.kerello@st.com, computersforpeace@gmail.com,
        devicetree@vger.kernel.org, dwmw2@infradead.org,
        geert@linux-m68k.org, juliensu@mxic.com.tw, lee.jones@linaro.org,
        liang.yang@amlogic.com, linux-kernel@vger.kernel.org,
        linux-mtd@lists.infradead.org, linux-spi@vger.kernel.org,
        marcel.ziswiler@toradex.com, marek.vasut@gmail.com,
        mark.rutland@arm.com, "Miquel Raynal" <miquel.raynal@bootlin.com>,
        paul.burton@mips.com, richard@nod.at, robh+dt@kernel.org,
        stefan@agner.ch, zhengxunli@mxic.com.tw
Subject: Re: [PATCH v3 2/4] mtd: rawnand: Add Macronix MX25F0A NAND controller
MIME-Version: 1.0
Message-ID: <OFC97D5691.B26644D3-ON48258423.002F8D47-48258423.00310B3E@mxic.com.tw>
From:   masonccyang@mxic.com.tw
Date:   Mon, 24 Jun 2019 16:55:41 +0800
Content-Type: text/plain; charset="US-ASCII"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


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@collabora.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.
> 
> Before you do that, can you please try to understand where the problem
> comes from and explain it to us? Hacking the NFC driver is only
> meaningful if the problem is on the NFC side. If your NAND chip does
> not support when the CS pin goes high between read_param_page_op() and
> read_data_op() the problem should be fixed in the core.

I think I have fixed the problem and the root cause is the our NFC's TX 
FIFO counter 
do a unnecessary reset in CS control function. Our NFC implement 
read-write 
buffer transfer to send command, address and data.
A unnecessary reset to TX FIFO will send a command byte out first and this 
extra
command will make something wrong to next operation.

For now, doing CS# control in ->exec_op() is OK to me.

thanks & best regards,
Mason


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