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From: Chris Ball <cjb@laptop.org>
To: Will Newton <will.newton@gmail.com>
Cc: Linux Kernel list <linux-kernel@vger.kernel.org>,
	linux-mmc@vger.kernel.org, Matt Fleming <matt@console-pimps.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] dw_mmc: Add Synopsys DesignWare mmc host driver.
Date: Sun, 12 Dec 2010 13:52:24 +0000	[thread overview]
Message-ID: <20101212135224.GA31812@void.printf.net> (raw)
In-Reply-To: <AANLkTin5aVPz5Y=jS89V00XS=rje3gqeUb2VTYt2A_9=@mail.gmail.com>

Hi Will,

On Sun, Dec 12, 2010 at 10:57:44AM +0000, Will Newton wrote:
> > drivers/mmc/host/dw_mmc.c: In function ‘dw_mci_pull_data64’:
> > drivers/mmc/host/dw_mmc.c:998: error: implicit declaration of function ‘__raw_readq’
> >
> > because arch/arm doesn't implement raw versions of these 64-bit accesses.
> > I'm surprised that this driver hasn't been compiled on ARM before!  What
> 
> That particular bit of code has been added since it was last built for
> arm. Our architecture can do 64bit accesses so we implement readq.
> Unfortunately there doesn't seem to be a sane way to conditionalize
> code for architectures that have or don't have readq, so I suspect
> I'll have to just remove that branch of the if statement for now.

(Russell, thanks for the excellent explanation.)

Other drivers (MTD, gpio/basic_mmio_gpio.c, fs/fuse, pcm_oss.c)
conditionalize uses of {read,write}q on BITS_PER_LONG >= 64, so
something like this:

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 7de6b42..526b5cb 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -988,10 +988,11 @@ static void dw_mci_pull_data32(struct dw_mci *host, void *buf, int cnt)
 		*pData++ = mci_readl(host, DATA);
 		cnt--;
 	}
 }
 
+#if BITS_PER_LONG >= 64
 static void dw_mci_push_data64(struct dw_mci *host, void *buf, int cnt)
 {
 	u64 *pData = (u64 *)buf;
 
 	WARN_ON(cnt % 8 != 0);
@@ -1013,10 +1014,11 @@ static void dw_mci_pull_data64(struct dw_mci *host, void *buf, int cnt)
 	while (cnt > 0) {
 		*pData++ = mci_readq(host, DATA);
 		cnt--;
 	}
 }
+#endif
 
 static void dw_mci_read_data_pio(struct dw_mci *host)
 {
 	struct scatterlist *sg = host->sg;
 	void *buf = sg_virt(sg);
@@ -1591,15 +1593,17 @@ static int dw_mci_probe(struct platform_device *pdev)
 	if (!i) {
 		host->push_data = dw_mci_push_data16;
 		host->pull_data = dw_mci_pull_data16;
 		width = 16;
 		host->data_shift = 1;
+#if BITS_PER_LONG >= 64
 	} else if (i == 2) {
 		host->push_data = dw_mci_push_data64;
 		host->pull_data = dw_mci_pull_data64;
 		width = 64;
 		host->data_shift = 3;
+#endif
 	} else {
 		/* Check for a reserved value, and warn if it is */
 		WARN((i != 1),
 			"HCON reports a reserved host data width!\n"
 			"Defaulting to 32-bit access.\n");


This is only useful if you just want the driver to compile (it compiles
on ARM after the above) and don't expect a working device if you find
the HCON programmed with 64-bit width on an ARM board, though.

Thanks,

-- 
Chris Ball   <cjb@laptop.org>   <http://printf.net/>
One Laptop Per Child

  reply	other threads:[~2010-12-12 13:52 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-12-06 15:53 [RESEND PATCH] " Will Newton
2010-12-08 11:55 ` Matt Fleming
2010-12-08 13:14   ` Will Newton
2010-12-08 14:21     ` [PATCH] " Will Newton
2010-12-08 16:07       ` Matt Fleming
2010-12-09  6:47       ` Chris Ball
2010-12-09 12:11         ` Will Newton
2010-12-09 16:01           ` Chris Ball
2010-12-09 17:24             ` Will Newton
     [not found]               ` <20101211192320.GA24430@void.printf.net>
2010-12-12  8:41                 ` Russell King - ARM Linux
2010-12-12 11:15                   ` Russell King - ARM Linux
2010-12-12 10:57                 ` Will Newton
2010-12-12 13:52                   ` Chris Ball [this message]
2010-12-12 14:03                     ` Will Newton
2010-12-12 14:11                       ` Russell King - ARM Linux
2010-12-12 14:31                         ` Will Newton
2010-12-12 14:47                           ` Russell King - ARM Linux
2010-12-12 15:17                             ` Will Newton
2010-12-16 17:04                 ` [PATCH v4] " Will Newton
2011-01-02  6:20                   ` Chris Ball
2011-01-18  7:54                   ` Jaehoon Chung
2011-01-18 10:21                     ` Will Newton
2011-02-08  6:38                       ` Jaehoon Chung
2011-02-08 10:29                         ` Will Newton
2011-02-08 10:49                           ` Jaehoon Chung
2011-02-08 12:06                             ` Will Newton
2010-12-09 17:35             ` [PATCH] " Chris Ball
2010-12-09 17:46               ` Will Newton
  -- strict thread matches above, loose matches on Subject: below --
2010-11-29 17:35 Will Newton

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