linux-kernel - Re: [PATCH v3 2/2] mtd: rawnand: meson: waiting w/o wired ready/busy pin

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Message-ID: <20230704151220.67857861@xps-13>
Date:   Tue, 4 Jul 2023 15:12:20 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Arseniy Krasnov <avkrasnov@...rdevices.ru>
Cc:     Liang Yang <liang.yang@...ogic.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        <oxffffaa@...il.com>, <kernel@...rdevices.ru>,
        <linux-mtd@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-amlogic@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/2] mtd: rawnand: meson: waiting w/o wired
 ready/busy pin

Hi Arseniy,

avkrasnov@...rdevices.ru wrote on Tue, 4 Jul 2023 15:46:18 +0300:

> On 04.07.2023 15:43, Miquel Raynal wrote:
> > Hi Arseniy,
> > 
> > AVKrasnov@...rdevices.ru wrote on Thu, 8 Jun 2023 07:47:28 +0300:
> >   
> >> If there is no wired ready/busy pin, classic way to wait for command
> >> completion is to use function 'nand_soft_waitrdy()'. Meson NAND has
> >> special command which allows to wait for NAND_STATUS_READY bit without
> >> reading status in a software loop (as 'nand_soft_waitrdy()' does). To
> >> use it send this command along with NAND_CMD_STATUS, then wait for an
> >> interrupt, and after interrupt send NAND_CMD_READ0. So this feature
> >> allows to use interrupt driven waiting without wired ready/busy pin.
> >>
> >> Suggested-by: Liang Yang <liang.yang@...ogic.com>
> >> Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
> >> ---
> >>  drivers/mtd/nand/raw/meson_nand.c | 77 +++++++++++++++++++++++++++++--
> >>  1 file changed, 73 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/mtd/nand/raw/meson_nand.c b/drivers/mtd/nand/raw/meson_nand.c
> >> index 074e14225c06..9f05e113b4ea 100644
> >> --- a/drivers/mtd/nand/raw/meson_nand.c
> >> +++ b/drivers/mtd/nand/raw/meson_nand.c
> >> @@ -38,6 +38,7 @@
> >>  #define NFC_CMD_SCRAMBLER_DISABLE	0
> >>  #define NFC_CMD_SHORTMODE_DISABLE	0
> >>  #define NFC_CMD_RB_INT		BIT(14)
> >> +#define NFC_CMD_RB_INT_NO_PIN	((0xb << 10) | BIT(18) | BIT(16))
> >>  
> >>  #define NFC_CMD_GET_SIZE(x)	(((x) >> 22) & GENMASK(4, 0))
> >>  
> >> @@ -179,6 +180,7 @@ struct meson_nfc {
> >>  	u32 info_bytes;
> >>  
> >>  	unsigned long assigned_cs;
> >> +	bool no_rb_pin;
> >>  };
> >>  
> >>  enum {
> >> @@ -392,7 +394,42 @@ static void meson_nfc_set_data_oob(struct nand_chip *nand,
> >>  	}
> >>  }
> >>  
> >> -static int meson_nfc_queue_rb(struct meson_nfc *nfc, int timeout_ms)
> >> +static int meson_nfc_wait_no_rb_pin(struct meson_nfc *nfc, int timeout_ms,
> >> +				    bool need_cmd_read0)
> >> +{
> >> +	u32 cmd, cfg;
> >> +
> >> +	meson_nfc_cmd_idle(nfc, nfc->timing.twb);
> >> +	meson_nfc_drain_cmd(nfc);
> >> +	meson_nfc_wait_cmd_finish(nfc, CMD_FIFO_EMPTY_TIMEOUT);
> >> +
> >> +	cfg = readl(nfc->reg_base + NFC_REG_CFG);
> >> +	cfg |= NFC_RB_IRQ_EN;
> >> +	writel(cfg, nfc->reg_base + NFC_REG_CFG);
> >> +
> >> +	reinit_completion(&nfc->completion);
> >> +	cmd = nfc->param.chip_select | NFC_CMD_CLE | NAND_CMD_STATUS;
> >> +	writel(cmd, nfc->reg_base + NFC_REG_CMD);
> >> +
> >> +	/* use the max erase time as the maximum clock for waiting R/B */
> >> +	cmd = NFC_CMD_RB | NFC_CMD_RB_INT_NO_PIN | nfc->timing.tbers_max;
> >> +	writel(cmd, nfc->reg_base + NFC_REG_CMD);
> >> +
> >> +	if (!wait_for_completion_timeout(&nfc->completion,
> >> +					 msecs_to_jiffies(timeout_ms)))
> >> +		return -ETIMEDOUT;
> >> +
> >> +	if (need_cmd_read0) {
> >> +		cmd = nfc->param.chip_select | NFC_CMD_CLE | NAND_CMD_READ0;
> >> +		writel(cmd, nfc->reg_base + NFC_REG_CMD);
> >> +		meson_nfc_drain_cmd(nfc);
> >> +		meson_nfc_wait_cmd_finish(nfc, CMD_FIFO_EMPTY_TIMEOUT);
> >> +	}  
> > 
> > I forgot about this, you should avoid open coding core helpers, can you
> > please send a followup patch to use nand_status_op() and
> > nand_exit_status_op() ?  
> 
> A ok, so:
> 1) Sending NAND_CMD_STATUS goes to nand_status_op()
> 2) Sending NAND_CMD_READ0 goes to nand_exit_status_op()
> 
> Ok, no problem! I'll prepare and send it on this week!

Exactly. Sorry I had this in mind but I likely forgot to write it
down.

Thanks,
Miquèl