RE: cfi_cmdset_0001.c: Excessive erase suspends

["Joakim Tjernlund" <Joakim.Tjernlund@transmode.se>]

> -----Original Message-----
> From: linux-mtd-bounces@lists.infradead.org [mailto:linux-mtd-bounces@lists.infradead.org] On Behalf
> Of Anders Grafström
> Sent: den 19 april 2008 00:11
> To: Jared Hulbert; Alexey Korolev; Linux-MTD Mailing List
> Subject: Re: cfi_cmdset_0001.c: Excessive erase suspends
> 
> Jared Hulbert wrote:
> > 2) Did you check that the MTD is configured to treat this flash with
> > the correct bus width?  I've been burned trying to figure out why a
> > 16bit configuration was missing half the data, turned out I had it
> > configured for 32bit MTD accesses.
> 
> I think I got it right.
> 
> > 3) I'd like to see that you can't use flash_eraseall and hexdump
> > /dev/mtdX to see this behavior.  Or maybe you could try to create a
> > simple test that would suspend an erase 10K times and verify the erase
> 
> See below.
> 
> > A solution might be an small delay before a
> > write suspends the erase.
> 
> udelay(100) right before the suspend command seems to work for me.
> It reduces the suspend count to about 1700 and no errors reported
> by JFFS2.
> 
> 
> I ran this routine in a standalone test program from u-boot:
> 
> void test_flash_erase_suspend(void)
> {
> 	volatile unsigned int *flash = (unsigned int *)0x41040000;
> 	unsigned int i;
> 	unsigned int suspends = 0;
> 	unsigned int words = 10;
> 
> 	/* Make sure there's something to erase */
> 	for (i = 0; i < 0x10000; i++) {
> 		if (flash[i] == 0xffffffff) {
> 			flash[i] = 0x00400040;
> 			flash[i] = 0;
> 			while ((flash[i] & 0x00800080) != 0x00800080);
> 		}
> 	}
> 
> 	/* Clear status */
> 	flash[0] = 0x00500050;
> 
> 	/* Erase */
> 	flash[0] = 0x00200020;
> 	flash[0] = 0x00d000d0;
> 
> 	while (1) {
> 		/* Suspend */
> 		flash[0] = 0x00b000b0;
> 		suspends++;
> 
> 		/* Short delay */
> 		for (i = 0; i < 1000; i++);
> 

Don't you need to check that the chip is suspended before you do any
new operation?

> 		/* Resume */
> 		flash[0] = 0x00d000d0;
> 		flash[0] = 0x00700070;
> 
> 		/* Erase done ? */
> 		if ((flash[i] & 0x00800080) == 0x00800080) {
> 			printf("\nStatus %08x\n", flash[i]);
> 			break;
> 		}
> 
> 		/* Short delay */
> 		for (i = 0; i < 3500; i++);
> 	}
> 
> 	/* Read array */
> 	flash[0] = 0x00ff00ff;
> 
> 	/* Show the first 10 failed words */
> 	for (i = 0; i < 0x10000; i++) {
> 		if (flash[i] != 0xffffffff) {
> 			printf("%08x\n", flash[i]);
> 			if (--words == 0)
> 				break;
> 		}
> 	}
> 
> 	printf("%d suspends\n", suspends);
> }