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Date:   Sun, 25 Aug 2019 15:28:10 +0200
From:   Boris Brezillon <boris.brezillon@collabora.com>
To:     <Tudor.Ambarus@microchip.com>
Cc:     <marek.vasut@gmail.com>, <vigneshr@ti.com>,
        <miquel.raynal@bootlin.com>, <richard@nod.at>,
        <linux-mtd@lists.infradead.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 4/5] mtd: spi-nor: Move clear_sr_bp() to 'struct
 spi_nor_flash_parameter'
Message-ID: <20190825152810.6fcac067@collabora.com>
In-Reply-To: <6485db42-4449-cc9b-8e09-0ad89b259a8b@microchip.com>
References: <20190823155325.13459-1-tudor.ambarus@microchip.com>
        <20190823155325.13459-5-tudor.ambarus@microchip.com>
        <20190825150927.5374b1ea@collabora.com>
        <6485db42-4449-cc9b-8e09-0ad89b259a8b@microchip.com>
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On Sun, 25 Aug 2019 13:19:57 +0000
<Tudor.Ambarus@microchip.com> wrote:

> On 08/25/2019 04:09 PM, Boris Brezillon wrote:
> > On Fri, 23 Aug 2019 15:53:41 +0000
> > <Tudor.Ambarus@microchip.com> wrote:
> >   
> >> From: Tudor Ambarus <tudor.ambarus@microchip.com>
> >>
> >> All flash parameters and settings should reside inside
> >> 'struct spi_nor_flash_parameter'. Move clear_sr_bp() from
> >> 'struct spi_nor' to 'struct spi_nor_flash_parameter'.
> >>
> >> Rename clear_sr_bp()/disable_block_protection() to better indicate
> >> what the function does.
> >>
> >> Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
> >> ---
> >>  drivers/mtd/spi-nor/spi-nor.c | 47 +++++++++++++++++++++++++++++++++----------
> >>  include/linux/mtd/spi-nor.h   |  5 ++---
> >>  2 files changed, 38 insertions(+), 14 deletions(-)
> >>
> >> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> >> index 6bd104c29cd9..15b0b1148bf3 100644
> >> --- a/drivers/mtd/spi-nor/spi-nor.c
> >> +++ b/drivers/mtd/spi-nor/spi-nor.c
> >> @@ -4477,20 +4477,45 @@ static int spi_nor_quad_enable(struct spi_nor *nor)
> >>  	return nor->params.quad_enable(nor);
> >>  }
> >>  
> >> +/**
> >> + * spi_nor_disable_block_protection() - Disable the write block protection
> >> + * during power-up.
> >> + * @nor:                pointer to a 'struct spi_nor'
> >> + *
> >> + * Some spi-nor flashes are write protected by default after a power-on reset
> >> + * cycle, in order to avoid inadvertend writes during power-up. Backward
> >> + * compatibility imposes to disable the write block protection at power-up
> >> + * by default.
> >> + *
> >> + * Return: 0 on success, -errno otherwise.
> >> + */
> >> +static int spi_nor_disable_block_protection(struct spi_nor *nor)
> >> +{
> >> +	if (!nor->params.disable_block_protection)
> >> +		return 0;
> >> +
> >> +	/*
> >> +	 * In case of the legacy quad enable requirements are set, if the
> >> +	 * configuration register Quad Enable bit is one, only the the
> >> +	 * Write Status (01h) command with two data bytes may be used to clear
> >> +	 * the block protection bits.
> >> +	 */
> >> +	if (nor->params.quad_enable == spansion_quad_enable)
> >> +		nor->params.disable_block_protection =
> >> +			spi_nor_spansion_clear_sr_bp;  
> > 
> > Hm, doesn't look right to adjust the function pointer just before
> > calling it. Can't we move that logic earlier (when doing the
> > default/manufacturer specific init)? Also, as I said in one of my  
> 
> No, we can't move it earlier to ->default_init() because the pointer to
> quad_enable() function can be modified later on, when parsing SFDP. This should
> stay here, after the quad_enable() method is known, so after the
> spi_nor_init_params() call.
> 
> 
> > previous emails, I'd prefer to have this hook moved to
> > spi_nor_locking_ops and just have a flag to reflect when block
> > protection can be disabled.  
> 
> yes, I agree, will move.

That won't work: ->locking_ops is const, meaning that you can't update
individual fields (which I consider a good thing). As I see it, the
locking scheme is a package that describe how to lock/unlock blocks, be
it individually, by groups or globally. I really hope we can take this
decision on a per-manufacturer basis, but I fear it might actually be a
per-chip thing.

> 
> >   
> >> +
> >> +	return nor->params.disable_block_protection(nor);
> >> +}
> >> +
> >>  static int spi_nor_init(struct spi_nor *nor)
> >>  {
> >>  	int err;
> >>  
> >> -	if (nor->clear_sr_bp) {
> >> -		if (nor->quad_enable == spansion_quad_enable)
> >> -			nor->clear_sr_bp = spi_nor_spansion_clear_sr_bp;
> >> -
> >> -		err = nor->clear_sr_bp(nor);
> >> -		if (err) {
> >> -			dev_err(nor->dev,
> >> -				"fail to clear block protection bits\n");
> >> -			return err;
> >> -		}
> >> +	err = spi_nor_disable_block_protection(nor);
> >> +	if (err) {
> >> +		dev_err(nor->dev,
> >> +			"fail to unlock the flash at init (err = %d)\n", err);
> >> +		return err;
> >>  	}
> >>  
> >>  	err = spi_nor_quad_enable(nor);
> >> @@ -4635,7 +4660,7 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
> >>  	    JEDEC_MFR(nor->info) == SNOR_MFR_INTEL ||
> >>  	    JEDEC_MFR(nor->info) == SNOR_MFR_SST ||
> >>  	    nor->info->flags & SPI_NOR_HAS_LOCK)
> >> -		nor->clear_sr_bp = spi_nor_clear_sr_bp;
> >> +		nor->params.disable_block_protection = spi_nor_clear_sr_bp;
> >>  
> >>  	/* Parse the Serial Flash Discoverable Parameters table. */
> >>  	ret = spi_nor_init_params(nor);
> >> diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
> >> index 17787238f0e9..399ac34a529d 100644
> >> --- a/include/linux/mtd/spi-nor.h
> >> +++ b/include/linux/mtd/spi-nor.h
> >> @@ -480,6 +480,7 @@ struct spi_nor;
> >>   * @page_programs:	page program capabilities ordered by priority: the
> >>   *                      higher index in the array, the higher priority.
> >>   * @quad_enable:	enables SPI NOR quad mode.
> >> + * @disable_block_protection: disables block protection during power-up.
> >>   */
> >>  struct spi_nor_flash_parameter {
> >>  	u64				size;
> >> @@ -490,6 +491,7 @@ struct spi_nor_flash_parameter {
> >>  	struct spi_nor_pp_command	page_programs[SNOR_CMD_PP_MAX];
> >>  
> >>  	int (*quad_enable)(struct spi_nor *nor);
> >> +	int (*disable_block_protection)(struct spi_nor *nor);
> >>  };
> >>  
> >>  /**
> >> @@ -535,8 +537,6 @@ struct flash_info;
> >>   * @flash_unlock:	[FLASH-SPECIFIC] unlock a region of the SPI NOR
> >>   * @flash_is_locked:	[FLASH-SPECIFIC] check if a region of the SPI NOR is
> >>   *			completely locked
> >> - * @clear_sr_bp:	[FLASH-SPECIFIC] clears the Block Protection Bits from
> >> - *			the SPI NOR Status Register.
> >>   * @params:		[FLASH-SPECIFIC] SPI-NOR flash parameters and settings.
> >>   *                      The structure includes legacy flash parameters and
> >>   *                      settings that can be overwritten by the spi_nor_fixups
> >> @@ -578,7 +578,6 @@ struct spi_nor {
> >>  	int (*flash_lock)(struct spi_nor *nor, loff_t ofs, uint64_t len);
> >>  	int (*flash_unlock)(struct spi_nor *nor, loff_t ofs, uint64_t len);
> >>  	int (*flash_is_locked)(struct spi_nor *nor, loff_t ofs, uint64_t len);
> >> -	int (*clear_sr_bp)(struct spi_nor *nor);
> >>  	struct spi_nor_flash_parameter params;
> >>  
> >>  	void *priv;  
> > 
> >