On 24/11/11 17:33, Voss, Nikolaus wrote: > Hi, > > Ben Dooks wrote on 2011-11-24: >> On Wed, Nov 23, 2011 at 04:35:55PM +0100, Nikolaus Voss wrote: >>> The old driver has two main deficencies: >>> i) No repeated start (Sr) condiction is possible, this makes it unusable >>> e.g. for most SMBus transfers. >>> ii) I/O was done with polling/busy waiting what caused over-/underruns >>> even at light system loads and clock speeds. >>> >>> The new driver overcomes these deficencies and in addition allows for >>> more than one TWI interface. >>> >>> A remaining limitation is the fact, that only one repeated start is >>> possible (two concatenated messages). This limitation is imposed by >>> the hardware. However, this should not be a problem as all common >>> i2c-client communication does not rely on more than one repeated start. >>> >>> v7: Patch 4/5: i) fix bug if internal address > 1 byte >>> ii) send stop when len == 1 >>> (both reported by Carsten Behling) >>> v6: Patch 5/5: support for I2C_SMBUS_BLOCK_DATA transfers. >>> Better use of clk_(un)prepare(). >>> More sensible transfer timeout. >>> v5: Another round of review comments from Ryan Mallon, Felipe Balbi >>> and Russell King: convert twi clk to use .dev_id, cleanups >>> v4: Integrated more review comments from Ryan Mallon and Felipe Balbi: >>> Moved register include file to local include, code cleanups >>> v3: Integrated review comments from Ryan Mallon and Felipe Balbi >>> v2: Fixed whitespace issue >>> >>> Nikolaus Voss (5): >>> drivers/i2c/busses/i2c-at91.c: remove broken driver >>> Replace clk_lookup.con_id with clk_lookup.dev_id entries for twi clk >>> drivers/i2c/busses/i2c-at91.c: add new driver >>> G45 TWI: remove open drain setting for twi function gpios >>> i2c-at91.c: add SMBUS_READ_BLOCK_DATA functionality >> >> Is the original driver so broken that the two could not co-exist, or are >> we making so many changes that there's no point in keeping the original >> one? > > The old driver was marked as broken for the above reasons and I can hardly > imagine any setup in which it would be preferable to i2c-gpio. So it does > not make any sense to keep the old driver alive. Though inspired by the old > driver, the new one is almost a rewrite from scratch, so for better reviewing, > I removed the old instead of doing a diff. I can confirm this. I worked on a number of AT91 based platforms with several different i2c client devices and we always had to use the i2c-gpio driver because the at91-i2c driver would not reliably work with our client devices. None of the at91 defconfigs select I2C_AT91, so it should be fairly safe to remove the old driver. Getting this driver into linux-next (if it isn't already) would be good so we can see if it does cause problems for anybody. Thanks, ~Ryan -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
