Re: [PATCH v4 2/3] mtd: spinand: use the spi-mem poll status APIs

[Patrice CHOTARD]

On 5/18/21 4:18 PM, Boris Brezillon wrote:
> On Tue, 18 May 2021 15:43:31 +0200
> <patrice.chotard@xxxxxxxxxxx> wrote:
> 
>> From: Patrice Chotard <patrice.chotard@xxxxxxxxxxx>
>>
>> Make use of spi-mem poll status APIs to let advanced controllers
>> optimize wait operations.
>> This should also fix the high CPU usage for system that don't have
>> a dedicated STATUS poll block logic.
>>
>> Signed-off-by: Patrice Chotard <patrice.chotard@xxxxxxxxxxx>
>> Signed-off-by: Christophe Kerello <christophe.kerello@xxxxxxxxxxx>
>> ---
>> Changes in v4:
>>   - Update commit message.
>>   - Add comment which explains how delays has been calculated.
>>   - Rename SPINAND_STATUS_TIMEOUT_MS to SPINAND_WAITRDY_TIMEOUT_MS.
>>
>> Changes in v3:
>>   - Add initial_delay_us and polling_delay_us parameters to spinand_wait()
>>   - Add SPINAND_READ/WRITE/ERASE/RESET_INITIAL_DELAY_US and
>>     SPINAND_READ/WRITE/ERASE/RESET_POLL_DELAY_US defines.
>>
>> Changes in v2:
>>   - non-offload case is now managed by spi_mem_poll_status()
>>
>>  drivers/mtd/nand/spi/core.c | 45 ++++++++++++++++++++++++++-----------
>>  include/linux/mtd/spinand.h | 22 ++++++++++++++++++
>>  2 files changed, 54 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
>> index 17f63f95f4a2..3131fae0c715 100644
>> --- a/drivers/mtd/nand/spi/core.c
>> +++ b/drivers/mtd/nand/spi/core.c
>> @@ -473,20 +473,26 @@ static int spinand_erase_op(struct spinand_device *spinand,
>>  	return spi_mem_exec_op(spinand->spimem, &op);
>>  }
>>  
>> -static int spinand_wait(struct spinand_device *spinand, u8 *s)
>> +static int spinand_wait(struct spinand_device *spinand,
>> +			unsigned long initial_delay_us,
>> +			unsigned long poll_delay_us,
>> +			u8 *s)
>>  {
>> -	unsigned long timeo =  jiffies + msecs_to_jiffies(400);
>> +	struct spi_mem_op op = SPINAND_GET_FEATURE_OP(REG_STATUS,
>> +						      spinand->scratchbuf);
>>  	u8 status;
>>  	int ret;
>>  
>> -	do {
>> -		ret = spinand_read_status(spinand, &status);
>> -		if (ret)
>> -			return ret;
>> +	ret = spi_mem_poll_status(spinand->spimem, &op, STATUS_BUSY, 0,
>> +				  initial_delay_us,
>> +				  poll_delay_us,
>> +				  SPINAND_WAITRDY_TIMEOUT_MS);
>> +	if (ret)
>> +		return ret;
>>  
>> -		if (!(status & STATUS_BUSY))
>> -			goto out;
>> -	} while (time_before(jiffies, timeo));
>> +	status = *spinand->scratchbuf;
>> +	if (!(status & STATUS_BUSY))
>> +		goto out;
> 
> Looks like you expect the driver to not only wait for a status change
> but also fill the data buffer with the last status value. I think that
> should be documented in the SPI mem API.

Right, i will update the API.

Thanks
Patrice
> 
>>  	/*
>>  	 * Extra read, just in case the STATUS_READY bit has changed
>> @@ -526,7 +532,10 @@ static int spinand_reset_op(struct spinand_device *spinand)
>>  	if (ret)
>>  		return ret;
>>  
>> -	return spinand_wait(spinand, NULL);
>> +	return spinand_wait(spinand,
>> +			    SPINAND_RESET_INITIAL_DELAY_US,
>> +			    SPINAND_RESET_POLL_DELAY_US,
>> +			    NULL);
>>  }
>>  
>>  static int spinand_lock_block(struct spinand_device *spinand, u8 lock)
>> @@ -549,7 +558,10 @@ static int spinand_read_page(struct spinand_device *spinand,
>>  	if (ret)
>>  		return ret;
>>  
>> -	ret = spinand_wait(spinand, &status);
>> +	ret = spinand_wait(spinand,
>> +			   SPINAND_READ_INITIAL_DELAY_US,
>> +			   SPINAND_READ_POLL_DELAY_US,
>> +			   &status);
>>  	if (ret < 0)
>>  		return ret;
>>  
>> @@ -585,7 +597,10 @@ static int spinand_write_page(struct spinand_device *spinand,
>>  	if (ret)
>>  		return ret;
>>  
>> -	ret = spinand_wait(spinand, &status);
>> +	ret = spinand_wait(spinand,
>> +			   SPINAND_WRITE_INITIAL_DELAY_US,
>> +			   SPINAND_WRITE_POLL_DELAY_US,
>> +			   &status);
>>  	if (!ret && (status & STATUS_PROG_FAILED))
>>  		return -EIO;
>>  
>> @@ -768,7 +783,11 @@ static int spinand_erase(struct nand_device *nand, const struct nand_pos *pos)
>>  	if (ret)
>>  		return ret;
>>  
>> -	ret = spinand_wait(spinand, &status);
>> +	ret = spinand_wait(spinand,
>> +			   SPINAND_ERASE_INITIAL_DELAY_US,
>> +			   SPINAND_ERASE_POLL_DELAY_US,
>> +			   &status);
>> +
>>  	if (!ret && (status & STATUS_ERASE_FAILED))
>>  		ret = -EIO;
>>  
>> diff --git a/include/linux/mtd/spinand.h b/include/linux/mtd/spinand.h
>> index 6bb92f26833e..6988956b8492 100644
>> --- a/include/linux/mtd/spinand.h
>> +++ b/include/linux/mtd/spinand.h
>> @@ -170,6 +170,28 @@ struct spinand_op;
>>  struct spinand_device;
>>  
>>  #define SPINAND_MAX_ID_LEN	4
>> +/*
>> + * For erase, write and read operation, we got the following timings :
>> + * tBERS (erase) 1ms to 4ms
>> + * tPROG 300us to 400us
>> + * tREAD 25us to 100us
>> + * In order to minimize latency, the min value is divided by 4 for the
>> + * initial delay, and dividing by 20 for the poll delay.
>> + * For reset, 5us/10us/500us if the device is respectively
>> + * reading/programming/erasing when the RESET occurs. Since we always
>> + * issue a RESET when the device is IDLE, 5us is selected for both initial
>> + * and poll delay.
>> + */
>> +#define SPINAND_READ_INITIAL_DELAY_US	6
>> +#define SPINAND_READ_POLL_DELAY_US	5
>> +#define SPINAND_RESET_INITIAL_DELAY_US	5
>> +#define SPINAND_RESET_POLL_DELAY_US	5
>> +#define SPINAND_WRITE_INITIAL_DELAY_US	75
>> +#define SPINAND_WRITE_POLL_DELAY_US	15
>> +#define SPINAND_ERASE_INITIAL_DELAY_US	250
>> +#define SPINAND_ERASE_POLL_DELAY_US	50
>> +
>> +#define SPINAND_WAITRDY_TIMEOUT_MS	400
>>  
>>  /**
>>   * struct spinand_id - SPI NAND id structure
>