linux-kernel - Re: [PATCH v2 1/3] spi: spi-mem: add automatic poll status functions

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Message-ID: <e70b13ba-7f65-7ff1-0517-94b39615dcdb@foss.st.com>
Date:   Mon, 17 May 2021 11:24:25 +0200
From:   Patrice CHOTARD <patrice.chotard@...s.st.com>
To:     Boris Brezillon <boris.brezillon@...labora.com>
CC:     Mark Brown <broonie@...nel.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        <linux-mtd@...ts.infradead.org>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        <linux-spi@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <christophe.kerello@...s.st.com>
Subject: Re: [PATCH v2 1/3] spi: spi-mem: add automatic poll status functions

Hi Boris

On 5/17/21 9:41 AM, Boris Brezillon wrote:
> On Fri, 7 May 2021 15:17:54 +0200
> <patrice.chotard@...s.st.com> wrote:
> 
>> +/**
>> + * spi_mem_poll_status() - Poll memory device status
>> + * @mem: SPI memory device
>> + * @op: the memory operation to execute
>> + * @mask: status bitmask to ckeck
>> + * @match: (status & mask) expected value
>> + * @timeout_ms: timeout in milliseconds
>> + *
>> + * This function send a polling status request to the controller driver
>> + *
>> + * Return: 0 in case of success, -ETIMEDOUT in case of error,
>> + *         -EOPNOTSUPP if not supported.
>> + */
>> +int spi_mem_poll_status(struct spi_mem *mem,
>> +			const struct spi_mem_op *op,
>> +			u16 mask, u16 match, u16 timeout_ms)
> 
> Maybe you should pass a delay_us too, to poll the status at the right
> rate in the SW-based case (can also be used by drivers if they need to

Ok, i will add a polling_rate_us parameter to poll_status() callback,
even if in STM32 driver case we will not use it, i agree it should be useful 
depending of driver's implementation.

> configure the polling rate). You could also add an initial_delay_us to
> avoid polling the status too early: an erase operation will take longer
> than a write which will take longer than a read. No need to check the
> status just after issuing the command, especially if the polling is
> done in SW. Those 2 arguments should also be passed to the driver.

Regarding the addition of an initial_delay_us. We got two solution:
  - use the same polling rate already used by read_poll_timeout() and 
    set read_poll_timeout()'s sleep_before_read parameter to true (in our case 20 us
    will be used as initial delay and as polling rate).

  - add an udelay(initial_delay_us) or even better usleep_range(initial_delay_us,
    initial_delay_us + delta) before calling read_poll_timeout().

I imagine you prefer the second solution ?

By adding polling_rate_us and initial_delay_us parameters to 
spi_mem_poll_status(), it implies to update all spinand_wait() calls for 
different operations (reset, read page, write page, erase) with respective  
initial_delay_us/polling_rate_us values for spi_mem_poll_status()'s parameters.

Can you provide adequate initial_delay_us and polling rate_us for each operation type ?.

Thanks
Patrice
> 
>> +{
>> +	struct spi_controller *ctlr = mem->spi->controller;
>> +	unsigned long ms;
>> +	int ret = -EOPNOTSUPP;
>> +	int exec_op_ret;
>> +	u16 *status;
>> +
>> +	if (!spi_mem_supports_op(mem, op))
>> +		return ret;
>> +
>> +	if (ctlr->mem_ops && ctlr->mem_ops->poll_status) {
>> +		ret = spi_mem_access_start(mem);
>> +		if (ret)
>> +			return ret;
>> +
>> +		reinit_completion(&ctlr->xfer_completion);
>> +
>> +		ret = ctlr->mem_ops->poll_status(mem, op, mask, match,
>> +						 timeout_ms);
>> +
>> +		ms = wait_for_completion_timeout(&ctlr->xfer_completion,
>> +						 msecs_to_jiffies(timeout_ms));
>> +
>> +		spi_mem_access_end(mem);
>> +		if (!ms)
>> +			return -ETIMEDOUT;
>> +	} else {
>> +		status = (u16 *)op->data.buf.in;
>> +		ret = read_poll_timeout(spi_mem_exec_op, exec_op_ret,
>> +					((*status) & mask) == match, 20,
>> +					timeout_ms * 1000, false, mem, op);
>> +		if (exec_op_ret)
>> +			return exec_op_ret;
>> +	}
>> +
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(spi_mem_poll_status);
>> +