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From: Miquel Raynal <miquel.raynal@bootlin.com>
To: masonccyang@mxic.com.tw
Cc: mark.rutland@arm.com, devicetree@vger.kernel.org,
	christophe.kerello@st.com, bbrezillon@kernel.org,
	juliensu@mxic.com.tw, lee.jones@linaro.org,
	linux-kernel@vger.kernel.org, robh+dt@kernel.org,
	linux-spi@vger.kernel.org, marcel.ziswiler@toradex.com,
	paul.burton@mips.com, broonie@kernel.org, geert@linux-m68k.org,
	stefan@agner.ch, linux-mtd@lists.infradead.org, richard@nod.at,
	liang.yang@amlogic.com, computersforpeace@gmail.com,
	dwmw2@infradead.org, marek.vasut@gmail.com,
	zhengxunli@mxic.com.tw
Subject: Re: [PATCH v3 2/4] mtd: rawnand: Add Macronix MX25F0A NAND controller
Date: Mon, 27 May 2019 14:42:50 +0200
Message-ID: <20190527144250.71908bd9@xps13> (raw)
In-Reply-To: <OFADC47344.0F9941B2-ON48258403.002336E3-48258403.003141F0@mxic.com.tw>

Hi Mason,

masonccyang@mxic.com.tw wrote on Thu, 23 May 2019 16:58:02 +0800:

> Hi Miquel,
> 
> > >   
> > > > > +
> > > > > +static void mxic_nand_select_chip(struct nand_chip *chip, int   
> chipnr) 
> > > > 
> > > > _select_target() is preferred now   
> > > 
> > > Do you mean I implement mxic_nand_select_target() to control #CS ?
> > > 
> > > If so, I need to call mxic_nand_select_target( ) to control #CS ON
> > > and then #CS OFF in _exec_op() due to nand_select_target()<in   
> nand_base,c>  
> > > is still calling chip->legacy.select_chip ?  
> > 
> > You must forget about the ->select_chip() callback. Now it should be
> > handled directly from the controller driver. Please have a look at the
> > commit pointed against the marvell_nand.c driver.  
> 
> I have no Marvell NFC datasheet and have one question.
> 
> In marvell_nand.c, there is no xxx_deselect_target() or 
> something like that doing #CS OFF.
> marvell_nfc_select_target() seems always to make one of chip or die
> #CS keep low.
> 
> Is it right ?

Yes, AFAIR there is no "de-assert" mechanism in this controller.

> 
> 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. 

So if you think it is not too time consuming and worth the trouble to
assert/deassert the CS at each operation, you may do it in your driver.


Thanks,
Miquèl

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Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-15  9:23 [PATCH v3 0/4] Add Macronix MX25F0A MFD driver for raw nand and spi Mason Yang
2019-04-15  9:23 ` [PATCH v3 1/4] mfd: Add Macronix MX25F0A MFD controller driver Mason Yang
2019-05-12 13:08   ` Miquel Raynal
2019-05-15  6:46     ` masonccyang
2019-04-15  9:23 ` [PATCH v3 2/4] mtd: rawnand: Add Macronix MX25F0A NAND controller Mason Yang
2019-05-12 13:18   ` Miquel Raynal
2019-05-15  8:48     ` masonccyang
2019-05-15 12:08       ` Miquel Raynal
     [not found]     ` <OF8A566F14.A2F0F576-ON482583FB.002E7E32-482583FB.003068B1@LocalDomain>
2019-05-15  9:18       ` masonccyang
2019-05-17  9:30     ` masonccyang
2019-05-20 12:23       ` Miquel Raynal
2019-05-23  8:58         ` masonccyang
2019-05-27 12:42           ` Miquel Raynal [this message]
2019-05-29  3:12             ` masonccyang
2019-06-17 12:35               ` Miquel Raynal
2019-06-18  1:24                 ` masonccyang
2019-06-18  6:14                   ` Boris Brezillon
2019-06-18  7:29                     ` Boris Brezillon
2019-06-19  8:04                       ` masonccyang
2019-06-19  8:09                         ` Miquel Raynal
2019-06-19  8:48                           ` masonccyang
2019-06-24  9:05                           ` masonccyang
2019-06-19  8:15                         ` Boris Brezillon
2019-06-19  8:55                           ` masonccyang
2019-06-19  9:06                             ` Boris Brezillon
2019-06-24  8:55                               ` masonccyang
2019-04-15  9:23 ` [PATCH v3 3/4] spi: Patch Macronix SPI controller driver according to MX25F0A MFD driver Mason Yang
2019-04-19 14:51   ` Mark Brown
     [not found]     ` <OF7742B4A9.445066F6-ON482583EC.0037E377-482583EC.0039125B@mxic.com.tw>
2019-05-02  2:41       ` Mark Brown
2019-04-15  9:23 ` [PATCH v3 4/4] dt-bindings: mfd: Document Macronix MX25F0A controller bindings Mason Yang
2019-04-26 22:41   ` Rob Herring
2019-05-12 13:23   ` Miquel Raynal
2019-05-15  7:36     ` masonccyang

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