Re: [PATCH v1] mtd: rawnand: meson: waiting w/o wired ready/busy pin

[Arseniy Krasnov]

On 07.06.2023 06:18, Liang Yang wrote:
> Hi Arseniy,
> 
> On 2023/6/7 3:51, Arseniy Krasnov wrote:
>> [ EXTERNAL EMAIL ]
>>
>> 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@xxxxxxxxxxx>
>> Signed-off-by: Arseniy Krasnov <AVKrasnov@xxxxxxxxxxxxxx>
>> ---
>>   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);
>> +
>> +       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;
> 
> NAND_CMD_READ0 should only be needed for reading operation, so we need skip the other operations here, such as programming and erase.

Done, removed in v2.

Thanks, Arseniy

> 
>> +       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) {
>> -- 
>> 2.35.0
>>