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Message-ID: <688909b3-fb0a-1001-d38e-57dba23d3bae@amlogic.com>
Date:   Wed, 7 Jun 2023 11:14:30 +0800
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Subject: Re: [PATCH v1] mtd: rawnand: meson: waiting w/o wired ready/busy pin
To:     Arseniy Krasnov <avkrasnov@sberdevices.ru>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Kevin Hilman <khilman@baylibre.com>,
        Jerome Brunet <jbrunet@baylibre.com>,
        Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Cc:     oxffffaa@gmail.com, kernel@sberdevices.ru,
        linux-mtd@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org,
        linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20230606195128.83432-1-AVKrasnov@sberdevices.ru>
 <2ed06841-6c9f-46c9-2d2d-2daffb0a9010@sberdevices.ru>
From:   Liang Yang <liang.yang@amlogic.com>
In-Reply-To: <2ed06841-6c9f-46c9-2d2d-2daffb0a9010@sberdevices.ru>
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Hi Arseniy,

On 2023/6/7 3:54, Arseniy Krasnov wrote:
> [ EXTERNAL EMAIL ]
> 
> On 06.06.2023 22:51, Arseniy Krasnov wrote:
>> 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@amlogic.com>
>> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>> ---
>>   drivers/mtd/nand/raw/meson_nand.c | 58 ++++++++++++++++++++++++++++++-
>>   1 file changed, 57 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mtd/nand/raw/meson_nand.c b/drivers/mtd/nand/raw/meson_nand.c
>> index 074e14225c06..f4c5309a9527 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))
>>
>> @@ -94,6 +95,7 @@
>>
>>   /* nand flash controller delay 3 ns */
>>   #define NFC_DEFAULT_DELAY    3000
>> +#define NFC_NO_RB_PIN_DELAY  5
>>
>>   #define ROW_ADDER(page, index)       (((page) >> (8 * (index))) & 0xff)
>>   #define MAX_CYCLE_ADDRS              5
>> @@ -179,6 +181,7 @@ struct meson_nfc {
>>        u32 info_bytes;
>>
>>        unsigned long assigned_cs;
>> +     bool no_rb_pin;
>>   };
>>
>>   enum {
>> @@ -392,7 +395,41 @@ 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)
>> +{
>> +     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);
>> +     meson_nfc_cmd_idle(nfc, NFC_NO_RB_PIN_DELAY);
> 
> ^^^
> 
>> +
>> +     /* 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);
>> +     meson_nfc_cmd_idle(nfc, NFC_NO_RB_PIN_DELAY);
> 
> ^^^
> Liang, I've implemented "new RB_INT" way instead of 'nand_soft_waitrdy()'. There were two numbers
> 2 and 5 in 'meson_nfc_cmd_idle()' as time argument (here and above). I've replaced both with
> define of 5 == NFC_NO_RB_PIN_DELAY. Is it correct? 2 and 5 were from doc?

You can do like that. as i know, bigger has no impact.
yes, them come from the example code of the controller datasheet; but i 
think we can delete them also.

> 
> Thanks, Arseniy
> 
>> +
>> +     if (!wait_for_completion_timeout(&nfc->completion,
>> +                                      msecs_to_jiffies(timeout_ms)))
>> +             return -ETIMEDOUT;
>> +
>> +     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);
>> +
>> +     return 0;
>> +}
>> +
>> +static int meson_nfc_wait_rb_pin(struct meson_nfc *nfc, int timeout_ms)
>>   {
>>        u32 cmd, cfg;
>>        int ret = 0;
>> @@ -420,6 +457,23 @@ static int meson_nfc_queue_rb(struct meson_nfc *nfc, int timeout_ms)
>>        return ret;
>>   }
>>
>> +static int meson_nfc_queue_rb(struct meson_nfc *nfc, int timeout_ms)
>> +{
>> +     if (nfc->no_rb_pin) {
>> +             /* This mode is used when there is no wired R/B pin.
>> +              * It works like 'nand_soft_waitrdy()', but instead of
>> +              * polling NAND_CMD_STATUS bit in the software loop,
>> +              * it will wait for interrupt - controllers checks IO
>> +              * bus and when it detects NAND_CMD_STATUS on it, it
>> +              * raises interrupt. After interrupt, NAND_CMD_READ0 is
>> +              * sent as terminator of the ready waiting procedure.
>> +              */
>> +             return meson_nfc_wait_no_rb_pin(nfc, timeout_ms);
>> +     } else {
>> +             return meson_nfc_wait_rb_pin(nfc, timeout_ms);
>> +     }
>> +}
>> +
>>   static void meson_nfc_set_user_byte(struct nand_chip *nand, u8 *oob_buf)
>>   {
>>        struct meson_nfc_nand_chip *meson_chip = to_meson_nand(nand);
>> @@ -1412,6 +1466,8 @@ static int meson_nfc_probe(struct platform_device *pdev)
>>                return ret;
>>        }
>>
>> +     nfc->no_rb_pin = !of_property_read_bool(dev->of_node, "nand-rb");
>> +
>>        writel(0, nfc->reg_base + NFC_REG_CFG);
>>        ret = devm_request_irq(dev, irq, meson_nfc_irq, 0, dev_name(dev), nfc);
>>        if (ret) {