Re: [PATCH v3 3/3] mtd: spinand: add SPI-NAND MTD resume handler

[Pratyush Yadav <p.yadav@xxxxxx>]

On 28/05/21 02:51PM, Patrice CHOTARD wrote:
> Hi Pratyush
> 
> On 5/28/21 2:05 PM, Pratyush Yadav wrote:
> > On 27/05/21 06:12PM, patrice.chotard@xxxxxxxxxxx wrote:
> >> From: Patrice Chotard <patrice.chotard@xxxxxxxxxxx>
> >>
> >> After power up, all SPI NAND's blocks are locked. Only read operations
> >> are allowed, write and erase operations are forbidden.
> >> The SPI NAND framework unlocks all the blocks during its initialization.
> >>
> >> During a standby low power, the memory is powered down, losing its
> >> configuration.
> >> During the resume, the QSPI driver state is restored but the SPI NAND
> >> framework does not reconfigured the memory.
> >>
> >> This patch adds SPI-NAND MTD PM handlers for resume ops.
> >> SPI NAND resume op re-initializes SPI NAND flash to its probed state.
> >>
> >> Signed-off-by: Christophe Kerello <christophe.kerello@xxxxxxxxxxx>
> >> Signed-off-by: Patrice Chotard <patrice.chotard@xxxxxxxxxxx>
> >> ---
> >> Changes in v3:
> >>   - Add spinand_read_cfg() call to repopulate cache
> >>
> >> Changes in v2:
> >>   - Add helper spinand_block_unlock().
> >>   - Add spinand_ecc_enable() call.
> >>   - Remove some dev_err().
> >>   - Fix commit's title and message.
> >>
> >>  drivers/mtd/nand/spi/core.c | 33 +++++++++++++++++++++++++++++++++
> >>  1 file changed, 33 insertions(+)
> >>
> >> diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
> >> index 1f699ad84f1b..e3fcbcf381c3 100644
> >> --- a/drivers/mtd/nand/spi/core.c
> >> +++ b/drivers/mtd/nand/spi/core.c
> >> @@ -1099,6 +1099,38 @@ static int spinand_block_unlock(struct spinand_device *spinand)
> >>  	return ret;
> >>  }
> >>  
> >> +static void spinand_mtd_resume(struct mtd_info *mtd)
> >> +{
> >> +	struct spinand_device *spinand = mtd_to_spinand(mtd);
> >> +	int ret;
> >> +
> >> +	ret = spinand_reset_op(spinand);
> >> +	if (ret)
> >> +		return;
> >> +
> >> +	ret = spinand_read_cfg(spinand);
> >> +	if (ret)
> >> +		return;
> >> +
> >> +	ret = spinand_init_quad_enable(spinand);
> >> +	if (ret)
> >> +		return;
> >> +
> >> +	ret = spinand_upd_cfg(spinand, CFG_OTP_ENABLE, 0);
> >> +	if (ret)
> >> +		return;
> >> +
> >> +	ret = spinand_manufacturer_init(spinand);
> >> +	if (ret)
> >> +		return;
> >> +
> >> +	ret = spinand_block_unlock(spinand);
> >> +	if (ret)
> >> +		return;
> >> +
> >> +	spinand_ecc_enable(spinand, false);
> >> +}
> >> +
> > 
> > I don't think you quite get what me and Miquel are suggesting.
> > 
> > The helper should call all these functions like read_cfg() 
> > quad_enable(), etc. So it should look something like:
> 
> Yes, this series was sent too quickly on my side, and i misunderstood 
> what you suggested, sorry for that.

Ah, I thought this was the v4. I see Miquel clarified already in reply 
to this patch.

> 
> > 
> > int spinand_init_flash()
> > {
> > 	ret = spinand_read_cfg(spinand);
> > 	if (ret)
> > 		return;
> > 
> 
> The new helper spinand_read_cfg() must not be called in spinand_init_flash()
> but directly in spinand_resume().
> This because spinand_read_cfg() only performs a REG_CFG read without doing the
> memory allocation of spinand->cfg_cache.
> 
> In spinand_init(), spinand_init_cfg_cache() must be called as previously as it does spinand->cfg_cache
> memory allocation and call the new helper spinand_read_cfg(). 
> Then after, spinand_init_flash() can be called.

I think it would be simpler for spinand_init_cfg_cache() to just 
allocate the spinand->cfg_cache array and then for spinand_init_flash() 
to call spinand_read_cfg().

> 
> > 	ret = spinand_init_quad_enable(spinand);
> > 	if (ret)
> > 		return;
> > 
> > 	ret = spinand_upd_cfg(spinand, CFG_OTP_ENABLE, 0);
> > 	if (ret)
> > 		return;
> > 
> > 	ret = spinand_manufacturer_init(spinand);
> > 	if (ret)
> > 		return;
> > 
> > 	ret = spinand_block_unlock(spinand);
> > 	if (ret)
> > 		return;
> > 
> > 	spinand_ecc_enable(spinand, false);
> > }
> > 
> > Then spinand_mtd_resume should look something like:
> > 
> > int spinand_mtd_resume()
> > {
> > 	ret = spinand_reset_op(spinand);
> > 	if (ret)
> > 		return;
> > 
> > 	return spinand_init_flash();
> > }
> > 
> > And spinand_init() should look something like:
> > 
> > int spinand_init()
> > {
> > 	...
> > 	spinand->oobbuf = ...
> > 
> > 	spinand_init_flash();
> > 
> > 	spinand_create_dirmaps();
> > 
> > 	...
> 
> As explained just above, spinand_init() will look like :
> 
> int spinand_init()
> {
> 	...
> 	spinand->oobbuf = ...
> 
> 	spinand_init_cfg_cache();     => perform cfg cache memory allocation and read the REG_CFG
> 
> 	spinand_init_flash();
> 
> 	spinand_create_dirmaps();
> 
> > }
> > 
> > 
> >>  static int spinand_init(struct spinand_device *spinand)
> >>  {
> >>  	struct device *dev = &spinand->spimem->spi->dev;
> >> @@ -1186,6 +1218,7 @@ static int spinand_init(struct spinand_device *spinand)
> >>  	mtd->_block_isreserved = spinand_mtd_block_isreserved;
> >>  	mtd->_erase = spinand_mtd_erase;
> >>  	mtd->_max_bad_blocks = nanddev_mtd_max_bad_blocks;
> >> +	mtd->_resume = spinand_mtd_resume;
> >>  
> >>  	if (nand->ecc.engine) {
> >>  		ret = mtd_ooblayout_count_freebytes(mtd);
> >> -- 
> >> 2.17.1
> > 
> 
> Thanks
> Patrice

-- 
Regards,
Pratyush Yadav
Texas Instruments Inc.