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

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Date:   Wed, 5 Jul 2023 09:07:03 +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 20:32:13 +0300:

> On 04.07.2023 16:07, Arseniy Krasnov wrote:
> > 
> > 
> > On 04.07.2023 16:12, Miquel Raynal wrote:  
> >> 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.  
> > 
> > Ok, got it!  
> 
> Hm, seems 'int nand_exit_status_op(struct nand_chip *chip)' is not exported,
> so I can't use it in the Meson module. While 'nand_status_op()' works ok.
> May I can export 'nand_exit_status_op()?'

Yes, in a separate patch please.

> 
> Thanks, Arseniy
> 
> 
> > 
> > Thanks, Arseniy
> >   
> >>
> >> Thanks,
> >> Miquèl  


Thanks,
Miquèl