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From: masonccyang@mxic.com.tw
To: "Miquel Raynal" <miquel.raynal@bootlin.com>
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: Wed, 29 May 2019 11:12:08 +0800
Message-ID: <OFE923A8E5.50375C30-ON48258409.0009AE1B-48258409.00119767@mxic.com.tw> (raw)
In-Reply-To: <20190527144250.71908bd9@xps13>


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. 

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().
i.e,. 

1) In nand_onfi_detect() to call nand_exec_op() twice by 
nand_read_param_page_op() and annd_read_data_op()

2) In nand_write_page_xxx to call nand_exec_op() many times by
nand_prog_page_begin_op(), nand_write_data_op() and 
nand_prog_page_end_op().


Should we consider to add a CS line controller in struct nand_controller
i.e,.

struct nand_controller {
         struct mutex lock;
         const struct nand_controller_ops *ops;
+          void (*select_chip)(struct nand_chip *chip, int cs);
};

to replace legacy.select_chip() ?


To patch in nand_select_target() and nand_deselect_target()

void nand_select_target(struct nand_chip *chip, unsigned int cs)
{
        /*
         * cs should always lie between 0 and chip->numchips, when that's 
not
         * the case it's a bug and the caller should be fixed.
         */
        if (WARN_ON(cs > chip->numchips))
                return;

        chip->cur_cs = cs;

+       if (chip->controller->select_chip)
+               chip->controller->select_chip(chip, cs);
+
        if (chip->legacy.select_chip)
                chip->legacy.select_chip(chip, cs);
}

void nand_deselect_target(struct nand_chip *chip)
{
+       if (chip->controller->select_chip)
+               chip->controller->select_chip(chip, -1);
+
        if (chip->legacy.select_chip)
                chip->legacy.select_chip(chip, -1);

        chip->cur_cs = -1;
}


> 
> 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

thanks & best regards,
Mason

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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
2019-05-29  3:12             ` masonccyang [this message]
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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