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

Miquel Raynal
2019-06-17T12:35:26Z

Hi Mason,

masonccyang@mxic.com.tw wrote on Wed, 29 May 2019 11:12:08 +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.
>
> 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().

Most of the chips today are CS-don't-care, which chip are you using?

Is this behavior publicly documented?

Is this LPM mode always activated?

> 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() ?
>

No, if really needed, we could add a "macro op done" flag in the nand
operation structure.

Thanks,
Miquèl