linux-kernel - Re: [PATCH v2] mtd: m25p80: Calculate flash block protect bits based on number of sectors

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Date:	Sun, 13 Apr 2014 19:24:03 +0200
From:	Marek Vasut <marex@...x.de>
To:	Austin Boyle <boyle.austin@...il.com>
Cc:	Gerlando Falauto <gerlando.falauto@...mile.com>,
	Brian Norris <computersforpeace@...il.com>,
	linux-mtd@...ts.infradead.org,
	David Woodhouse <dwmw2@...radead.org>,
	linux-kernel@...r.kernel.org,
	Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>,
	Angus Clark <angus.clark@...com>
Subject: Re: [PATCH v2] mtd: m25p80: Calculate flash block protect bits based on number of sectors

On Sunday, April 06, 2014 at 01:19:59 PM, Austin Boyle wrote:
[...]

> @@ -752,24 +773,18 @@ static int m25p80_lock(struct mtd_info *mtd, loff_t
> ofs, uint64_t len)
> 
>  	status_old = read_sr(flash);
> 
> -	if (offset < flash->mtd.size-(flash->mtd.size/2))
> -		status_new = status_old | SR_BP2 | SR_BP1 | SR_BP0;
> -	else if (offset < flash->mtd.size-(flash->mtd.size/4))
> -		status_new = (status_old & ~SR_BP0) | SR_BP2 | SR_BP1;
> -	else if (offset < flash->mtd.size-(flash->mtd.size/8))
> -		status_new = (status_old & ~SR_BP1) | SR_BP2 | SR_BP0;
> -	else if (offset < flash->mtd.size-(flash->mtd.size/16))
> -		status_new = (status_old & ~(SR_BP0|SR_BP1)) | SR_BP2;
> -	else if (offset < flash->mtd.size-(flash->mtd.size/32))
> -		status_new = (status_old & ~SR_BP2) | SR_BP1 | SR_BP0;
> -	else if (offset < flash->mtd.size-(flash->mtd.size/64))
> -		status_new = (status_old & ~(SR_BP2|SR_BP0)) | SR_BP1;
> -	else
> -		status_new = (status_old & ~(SR_BP2|SR_BP1)) | SR_BP0;
> +	for (lock_bits = 1; lock_bits < 7; lock_bits++) {
> +		protected_area_start = flash->mtd.size -
> +					get_protected_area(flash, lock_bits);
> +		if (offset >= protected_area_start)
> +			break;
> +	}
> +
> +	status_new = (status_old & ~SR_BP_BIT_MASK) |
> +			((lock_bits << SR_BP_BIT_OFFSET) & SR_BP_BIT_MASK);

This portion of code looks like a duplicate of ...

>  	/* Only modify protection if it will not unlock other areas */
> -	if ((status_new&(SR_BP2|SR_BP1|SR_BP0)) >
> -					(status_old&(SR_BP2|SR_BP1|SR_BP0))) {
> +	if ((status_new & SR_BP_BIT_MASK) > (status_old & SR_BP_BIT_MASK)) {
>  		write_enable(flash);
>  		if (write_sr(flash, status_new) < 0) {
>  			res = 1;
> @@ -786,6 +801,8 @@ static int m25p80_unlock(struct mtd_info *mtd, loff_t
> ofs, uint64_t len) struct m25p *flash = mtd_to_m25p(mtd);
>  	uint32_t offset = ofs;
>  	uint8_t status_old, status_new;
> +	uint8_t lock_bits;
> +	uint32_t protected_area_start;
>  	int res = 0;
> 
>  	mutex_lock(&flash->lock);
> @@ -797,24 +814,19 @@ static int m25p80_unlock(struct mtd_info *mtd, loff_t
> ofs, uint64_t len)
> 
>  	status_old = read_sr(flash);
> 
> -	if (offset+len > flash->mtd.size-(flash->mtd.size/64))
> -		status_new = status_old & ~(SR_BP2|SR_BP1|SR_BP0);
> -	else if (offset+len > flash->mtd.size-(flash->mtd.size/32))
> -		status_new = (status_old & ~(SR_BP2|SR_BP1)) | SR_BP0;
> -	else if (offset+len > flash->mtd.size-(flash->mtd.size/16))
> -		status_new = (status_old & ~(SR_BP2|SR_BP0)) | SR_BP1;
> -	else if (offset+len > flash->mtd.size-(flash->mtd.size/8))
> -		status_new = (status_old & ~SR_BP2) | SR_BP1 | SR_BP0;
> -	else if (offset+len > flash->mtd.size-(flash->mtd.size/4))
> -		status_new = (status_old & ~(SR_BP0|SR_BP1)) | SR_BP2;
> -	else if (offset+len > flash->mtd.size-(flash->mtd.size/2))
> -		status_new = (status_old & ~SR_BP1) | SR_BP2 | SR_BP0;
> -	else
> -		status_new = (status_old & ~SR_BP0) | SR_BP2 | SR_BP1;
> +	for (lock_bits = 1; lock_bits < 7; lock_bits++) {
> +		protected_area_start = flash->mtd.size -
> +					get_protected_area(flash, lock_bits);
> +		if (offset+len >= protected_area_start)
> +			break;
> +	}
> +	lock_bits--;
> +
> +	status_new = (status_old & ~SR_BP_BIT_MASK) |
> +			((lock_bits << SR_BP_BIT_OFFSET) & SR_BP_BIT_MASK);

... this here (if you don't consider the lock_bits--) . Why don't we move this 
into a separate function to avoid the duplication?

>  	/* Only modify protection if it will not lock other areas */
> -	if ((status_new&(SR_BP2|SR_BP1|SR_BP0)) <
> -					(status_old&(SR_BP2|SR_BP1|SR_BP0))) {
> +	if ((status_new & SR_BP_BIT_MASK) < (status_old & SR_BP_BIT_MASK)) {
>  		write_enable(flash);
>  		if (write_sr(flash, status_new) < 0) {
>  			res = 1;
> @@ -826,6 +838,39 @@ err:	mutex_unlock(&flash->lock);
>  	return res;
>  }
> 
> +static int m25p80_is_locked(struct mtd_info *mtd, loff_t ofs, uint64_t
> len) +{
> +	struct m25p *flash = mtd_to_m25p(mtd);
> +	uint32_t offset = ofs;
> +	uint8_t status;
> +	uint8_t lock_bits;
> +	uint32_t protected_area_start;
> +	int res;
> +
> +	mutex_lock(&flash->lock);
> +	/* Wait until finished previous command */
> +	if (wait_till_ready(flash)) {
> +		mutex_unlock(&flash->lock);
> +		return -EBUSY;
> +	}
> +	status = read_sr(flash);
> +	mutex_unlock(&flash->lock);
> +
> +	lock_bits = ((status & SR_BP_BIT_MASK) >> SR_BP_BIT_OFFSET);

Excessive () , the outer ones are not needed.

> +
> +	protected_area_start = flash->mtd.size -
> +					get_protected_area(flash, lock_bits);

You might want to introduce some "get_protected_area_size()" here, since this is 
the third time I see this call.

Otherwise nice, thanks for cleaning this mess up, it really helps !
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