From: Mason <slash.tmp@free.fr>
To: Pavel Machek <pavel@ucw.cz>,
Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Richard Weinberger <richard@nod.at>,
David Woodhouse <dwmw2@infradead.org>,
Brian Norris <computersforpeace@gmail.com>,
Marek Vasut <marek.vasut@gmail.com>,
Cyrille Pitchen <cyrille.pitchen@wedev4u.fr>,
linux-mtd <linux-mtd@lists.infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
mark.marshall@omicronenergy.com, b44839@freescale.com,
prabhakar@freescale.com
Subject: Re: [PATCH] nand_base: optimize checking of erased buffers
Date: Wed, 17 May 2017 13:39:16 +0200 [thread overview]
Message-ID: <911d0a3d-1be8-31a6-3bd1-c173ec6435ad@free.fr> (raw)
In-Reply-To: <421c46b9-288f-42e9-5b2f-d93af1e8a418@free.fr>
On 17/05/2017 13:27, Mason wrote:
> On 21/04/2017 12:51, Pavel Machek wrote:
>
>> If we see ~0UL in flash, there's no need for hweight, and no need to
>> check number of bitflips. So this should be net win.
>>
>> Signed-off-by: Pavel Machek <pavel@denx.de>
>>
>> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
>> index b0524f8..96c27ec 100644
>> --- a/drivers/mtd/nand/nand_base.c
>> +++ b/drivers/mtd/nand/nand_base.c
>> @@ -1357,7 +1357,10 @@ static int nand_check_erased_buf(void *buf, int len, int bitflips_threshold)
>>
>> for (; len >= sizeof(long);
>> len -= sizeof(long), bitmap += sizeof(long)) {
>> - weight = hweight_long(*((unsigned long *)bitmap));
>
> I hadn't noticed this earlier. There is, obviously, an implicit
> requirement that 'buf' must be 4-byte aligned on 32-bit platforms,
> and 8-byte aligned on 64-bit platforms.
>
> This is not true for my platform, as the ecc pointer is
> chip->oob_poi + 10
Doh! As Boris points out, the prologue/epilogue handle
all alignment & size issues.
Regards.
next prev parent reply other threads:[~2017-05-17 11:40 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-19 12:13 fsl_ifc_nand: are blank pages protected by ECC? Pavel Machek
2017-04-19 21:18 ` Boris Brezillon
2017-04-19 22:15 ` Pavel Machek
2017-04-19 22:27 ` Boris Brezillon
2017-04-20 11:40 ` Pavel Machek
2017-04-20 12:15 ` Boris Brezillon
2017-04-21 10:51 ` [PATCH] nand_base: optimize checking of erased buffers Pavel Machek
2017-05-17 11:27 ` Mason
2017-05-17 11:39 ` Mason [this message]
2017-05-17 11:52 ` Pavel Machek
2017-05-17 12:22 ` [PATCH] fsl_ifc_nand: fix handing of bit flips in erased nand Pavel Machek
2017-05-17 12:32 ` Boris Brezillon
2017-05-17 13:00 ` Pavel Machek
2017-05-17 13:25 ` Boris Brezillon
2017-05-17 20:03 ` [PATCH] mtd: nand: fsl_ifc: fix handing of bit flips in erased pages Pavel Machek
2017-05-31 20:59 ` [PATCHv2] " Pavel Machek
2017-05-31 22:59 ` Darwin Dingel
2017-06-01 1:09 ` Darwin Dingel
2017-06-01 13:12 ` Pavel Machek
2017-06-01 13:21 ` Boris Brezillon
2017-06-07 7:31 ` Boris Brezillon
2017-04-21 10:08 ` fsl_ifc_nand: are blank pages protected by ECC? Pavel Machek
2017-04-21 10:12 ` Richard Weinberger
2017-04-21 12:04 ` Boris Brezillon
2017-04-21 13:37 ` Pavel Machek
2017-04-21 13:49 ` Boris Brezillon
2017-04-22 7:01 ` Pavel Machek
2017-04-22 10:40 ` [PATCH] tango_nand.c: fix ecc.stats_corrected in empty flash case Pavel Machek
2017-04-23 9:58 ` tango_nand: is logic right in error cases? (was Re: fsl_ifc_nand: are blank pages protected by ECC?) Pavel Machek
2017-04-24 7:12 ` Boris Brezillon
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