From: Pierre Ossman <drzeus@drzeus.cx>
To: avorontsov@ru.mvista.com
Cc: Ben Dooks <ben-linux@fluff.org>, Arnd Bergmann <arnd@arndb.de>,
Kumar Gala <galak@kernel.crashing.org>,
Liu Dave <DaveLiu@freescale.com>,
sdhci-devel@list.drzeus.cx, linux-kernel@vger.kernel.org,
linuxppc-dev@ozlabs.org
Subject: Re: [PATCH 02/11] sdhci: Add support for bus-specific IO memory accessors
Date: Sat, 21 Feb 2009 16:57:57 +0100 [thread overview]
Message-ID: <20090221165757.22747648@mjolnir.ossman.eu> (raw)
In-Reply-To: <20090213144039.GA19572@oksana.dev.rtsoft.ru>
[-- Attachment #1: Type: text/plain, Size: 2701 bytes --]
On Fri, 13 Feb 2009 17:40:39 +0300
Anton Vorontsov <avorontsov@ru.mvista.com> wrote:
>
> No, on eSDHC the registers are big-endian, 32-bit width, with, for
> example, two 16-bit "logical" registers packed into it.
>
> That is,
>
> 0x4 0x5 0x6 0x7
> |~~~~~~~~:~~~~~~~~|
> | BLKCNT : BLKSZ |
> |________:________|
> 31 0
>
> ( The register looks wrong, right? BLKSZ should be at 0x4. But imagine
> that you swapped bytes in this 32 bit register... then the registers
> and their byte addresses will look normal. )
>
> So if we try to issue readw(SDHCI_BLOCK_SIZE), i.e. readw(0x4):
>
> - We'll read BLKCNT, while we wanted BLKSZ. This is because the
> address bits should be translated before we try word or byte
> reads/writes.
> - On powerpc read{l,w}() convert the read value from little-endian
> to big-endian byte order, which is wrong for our case (the
> register is big-endian already).
>
> That means that we have to convert address, but we don't want to
> convert the result of read/write ops.
>
*cries*
Now this is just incredibly horrible. Why the hell did they try to use
the sdhci interface and then do stupid things like this?
> > > +static inline void sdhci_writel(struct sdhci_host *host, u32 val, int reg)
> > > +{
> > > + host->writel(host, val, reg);
> > > +}
> >
> > Having to override these are worst case scenario
>
> Hm. It's not a worst case scenario, it's a normal scenario for
> eSDHC. Why should we treat eSDHC as a second-class citizen?
>
Because it's complete and utter crap. Freescale has completely ignored
the basic register interface requirements of the SDHCI spec. Treating
eSDHC as a second-class citizen is generous IMO.
> > as far as I'm
> > concerned, so I'd prefer something like:
> >
> > if (!host->ops->writel)
> > writel(host->ioaddr + reg, val);
> > else
> > host->ops->writel(host, val, reg);
>
> Surely the overhead isn't measurable... but why we purposely make
> things worse?
>
We can most likely do some micro-optimisation do make the compare part
cheaper, but the point was to avoid a function call for all the
properly implemented controllers out there. We could have a flag so
that it only has to check host->flags, which will most likely be in the
cache anyway.
Overhead for eSDHC is not a concern in my book, what is interesting is
how much this change slows things down for other controllers.
Rgds
--
-- Pierre Ossman
WARNING: This correspondence is being monitored by the
Swedish government. Make sure your server uses encryption
for SMTP traffic and consider using PGP for end-to-end
encryption.
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 198 bytes --]
next prev parent reply other threads:[~2009-02-21 15:58 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-06 18:05 [PATCH RFC 0/11] FSL eSDHC support: second call for comments Anton Vorontsov
2009-02-06 18:06 ` [PATCH 01/11] sdhci: Add quirk for controllers with no end-of-busy IRQ Anton Vorontsov
2009-02-06 18:06 ` [PATCH 02/11] sdhci: Add support for bus-specific IO memory accessors Anton Vorontsov
2009-02-08 20:50 ` Pierre Ossman
2009-02-13 14:40 ` Anton Vorontsov
2009-02-21 15:57 ` Pierre Ossman [this message]
2009-03-04 17:46 ` Anton Vorontsov
2009-03-08 14:08 ` Pierre Ossman
2009-02-06 18:06 ` [PATCH 03/11] sdhci: Add type checking for " Anton Vorontsov
2009-02-08 20:53 ` Pierre Ossman
2009-02-06 18:06 ` [PATCH 04/11] sdhci: Add support for card-detection polling Anton Vorontsov
2009-02-08 20:57 ` Pierre Ossman
2009-02-06 18:06 ` [PATCH 05/11] sdhci: Add support for hosts reporting inverted write-protect state Anton Vorontsov
2009-02-06 18:06 ` [PATCH 06/11] sdhci: Add support for hosts with strict 32 bit addressing Anton Vorontsov
2009-02-06 18:06 ` [PATCH 07/11] sdhci: Add quirk to suppress PIO interrupts during DMA transfers Anton Vorontsov
2009-02-08 21:02 ` Pierre Ossman
2009-02-06 18:06 ` [PATCH 08/11] sdhci: Add support for hosts that don't specify clocks in the cap. register Anton Vorontsov
2009-02-08 21:04 ` Pierre Ossman
2009-02-06 18:06 ` [PATCH 09/11] sdhci: Add set_clock callback Anton Vorontsov
2009-02-08 21:06 ` Pierre Ossman
2009-02-06 18:07 ` [PATCH 10/11] sdhci: Add quirk for Freescale eSDHC controllers Anton Vorontsov
2009-02-08 21:12 ` Pierre Ossman
2009-02-13 14:42 ` Anton Vorontsov
2009-02-06 18:07 ` [PATCH 11/11] mmc: Add OpenFirmware bindings for SDHCI driver Anton Vorontsov
2009-02-08 20:33 ` [PATCH RFC 0/11] FSL eSDHC support: second call for comments Pierre Ossman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20090221165757.22747648@mjolnir.ossman.eu \
--to=drzeus@drzeus.cx \
--cc=DaveLiu@freescale.com \
--cc=arnd@arndb.de \
--cc=avorontsov@ru.mvista.com \
--cc=ben-linux@fluff.org \
--cc=galak@kernel.crashing.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@ozlabs.org \
--cc=sdhci-devel@list.drzeus.cx \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).