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Message-ID: <20120531142540.GA4785@bitwizard.nl> Date: Thu, 31 May 2012 16:25:40 +0200 From: Rogier Wolff <R.E.Wolff@...Wizard.nl> To: Florian Fainelli <florian@...nwrt.org> Cc: Rogier Wolff <R.E.Wolff@...wizard.nl>, linux-kernel@...r.kernel.org, linux-mips@...ux-mips.org Subject: Re: BCM36xx support. Hi Florian, On Thu, May 31, 2012 at 03:55:34PM +0200, Florian Fainelli wrote: > First of all, you should have CC'd linux-mips, because that's where > BCM63xx development happens. As I'm not familiar with mips-development, I didn't know that. > On Wednesday 18 April 2012 07:51:40 Rogier Wolff wrote: > > > > While working on SPI and I2C support for the BCM2835, I found the > > BCM63xx SPI driver in the kernel. Turns out that this support > > was partially merged: > > > > The support can only be enabled when BCM63xx configuration symbol > > is defined which menuconfig lists as: > > > > Symbol: BCM63XX [=BCM63XX] > > Type : unknown > > > > I'd say the definition of this is not possible through the normal > > channels. > > > > And in the driver (drivers/spi/spi-bcm63xx.c) I see: > > > > #include <bcm63xx_dev_spi.h> > > > > but that file is not in the current git release. > > No, it did not make it for a reason I ignore, probably miscommunication. > > > > > (some more googling has resulted in me finding out that I don't want > > to know how the 63xx SPI controller works as it's for a MIPS processor > > while the 2835 is ARM). > And so? if the core is the same, just use it on your platform > too. If you have a look at the architecture files, you will see that > the various BCM63xx SoC have their internal registers shuffled but > the SPI core is always software compatible, another set of registers > can be added for BCM2835. I expect the core to be very different because they are for different processors. But of course if they are the same, a single driver would be better. However, with the header file missing, I can't find if the register offsets are the same. That would be a hint that the module is the the same. Reading the driver I see lots "readb" and "writeb" calls. These presumably read/write a byte. The '2835 module doesn't have any byte-registers. All registers are 32bits. I consider this a further hint that the modules are not the same. I've read some of the code, and for instance, there seems to be a limited-width register (3 or 4 bits) that specify the clock rate on the bcm63xx. On the bcm2835 the clock is set by good chunk (15 bits IIRC) of a 32-bit register which specifies the clock divisor. The core clock runs at 250MHz, so I can specify clock rates at with 1:250 accuracy around 1MHz. (i.e. 1000000 Hz is possible as well as 1004000) I consider this a further hint that the modules are not the same. So with three of those hints I'll take the hint that they are not the same, and concentrate on building a new driver for the bcm2835 (and 2708?) Roger. -- ** R.E.Wolff@...Wizard.nl ** http://www.BitWizard.nl/ ** +31-15-2600998 ** ** Delftechpark 26 2628 XH Delft, The Netherlands. KVK: 27239233 ** *-- BitWizard writes Linux device drivers for any device you may have! --* The plan was simple, like my brother-in-law Phil. But unlike Phil, this plan just might work. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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