[OpenWrt-Devel] Rebooting boards with > 16M SPI flash (was: Re: help)

[John Crispin]

Hi Paul,

looks good to me but i will run this past linux-mtd and ask them for an
opinion before merging it.

	John

On 08/07/2015 14:00, Paul Fertser wrote:
> Hi,
> 
> ldy647 <ldy647 at 163.com> writes:
>> recently, when we install our wireless router, we found when we run
>> the reboot command, the board couldn't restart. We hope you could lend
>> us a hand to solve this problem. We'll be quite grateful for what you
>> do for us.
> 
> Apparently MT7620 can't handle 4 byte addressing mode of the flash
> memory on hardware (probably ROM bootloader) level so it needs to be
> reset somehow prior to resetting the SoC. Some SoCs have a special
> output from the watchdog to reset all the on-board peripherals, it
> should be connected to the !RESET pin of the flash as well. And the
> kernel should then use the watchdog driver to cause a reboot.
> 
> As a workaround when hardware modification is not possible and the
> flash IC supports a reset command, you can use a patch like this (in
> some cases when the kernel is completely stuck it won't help to reboot
> of course, as the watchdog will fire on hardware level automatically,
> if configured):
> 
> diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
> index b298466..932f307 100644
> --- a/drivers/mtd/devices/m25p80.c
> +++ b/drivers/mtd/devices/m25p80.c
> @@ -21,6 +21,7 @@
>  #include <linux/module.h>
>  #include <linux/device.h>
>  #include <linux/interrupt.h>
> +#include <linux/reboot.h>
>  #include <linux/mutex.h>
>  #include <linux/math64.h>
>  #include <linux/slab.h>
> @@ -61,6 +62,9 @@
>  /* Used for Spansion flashes only. */
>  #define	OPCODE_BRWR		0x17	/* Bank register write */
>  
> +#define OPCODE_RESET_ENABLE	0x66
> +#define OPCODE_RESET		0x99
> +
>  /* Status Register bits. */
>  #define	SR_WIP			1	/* Write in progress */
>  #define	SR_WEL			2	/* Write enable latch */
> @@ -907,6 +911,21 @@ static const struct spi_device_id *jedec_probe(struct spi_device *spi)
>  	return ERR_PTR(-ENODEV);
>  }
>  
> +static int m25p80_reboot(struct notifier_block *nb, unsigned long val,
> +			       void *v)
> +{
> +	struct mtd_info *mtd;
> +
> +	mtd = container_of(nb, struct mtd_info, reboot_notifier);
> +	struct m25p *flash = mtd_to_m25p(mtd);
> +
> +	flash->command[0] = OPCODE_RESET_ENABLE;
> +	spi_write(flash->spi, flash->command, 1);
> +	flash->command[0] = OPCODE_RESET;
> +	spi_write(flash->spi, flash->command, 1);
> +
> +	return NOTIFY_DONE;
> +}
>  
>  /*
>   * board specific setup should have ensured the SPI clock used here
> @@ -1010,6 +1029,7 @@ static int m25p_probe(struct spi_device *spi)
>  	flash->mtd.size = info->sector_size * info->n_sectors;
>  	flash->mtd._erase = m25p80_erase;
>  	flash->mtd._read = m25p80_read;
> +	flash->mtd.reboot_notifier.notifier_call = m25p80_reboot;
>  
>  	/* flash protection support for STmicro chips */
>  	if (JEDEC_MFR(info->jedec_id) == CFI_MFR_ST) {
> @@ -1085,6 +1105,7 @@ static int m25p_probe(struct spi_device *spi)
>  				flash->mtd.eraseregions[i].numblocks);
>  
>  
> +	register_reboot_notifier(&flash->mtd.reboot_notifier);
>  	/* partitions should match sector boundaries; and it may be good to
>  	 * use readonly partitions for writeprotected sectors (BP2..BP0).
>  	 */
> @@ -1099,6 +1120,8 @@ static int m25p_remove(struct spi_device *spi)
>  	struct m25p	*flash = dev_get_drvdata(&spi->dev);
>  	int		status;
>  
> +	unregister_reboot_notifier(&flash->mtd.reboot_notifier);
> +
>  	/* Clean up MTD stuff. */
>  	status = mtd_device_unregister(&flash->mtd);
>  	if (status == 0) {
> 
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