Re: [PATCH] i2c: davinci: Fix bus rate calculation on Keystone SoC

[Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>]

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On Thu, Jun 18, 2015 at 12:22:33PM -0400, Murali Karicheri wrote:
> On 06/18/2015 05:00 AM, Sekhar Nori wrote:
> >On Thursday 18 June 2015 02:23 PM, Alexander Sverdlin wrote:
> >>According to KeyStone Architecture I2C User Guide,
> >>
> >>                          module clock frequency
> >>master clock frequency = ----------------------
> >>                          (ICCL + 6) + (ICCH + 6)
> >>
> >>i.e. "d" in i2c_davinci_calc_clk_dividers() should be fixed and
> >>not dependent from module clock prescaler PSC on these SoCs.
> >>
> >>Signed-off-by: Alexander Sverdlin <alexander.sverdlin-xNZwKgViW5gAvxtiuMwx3w@public.gmane.org>
> >>---
> >>
> >>RFC: If someone from TI has an idea how to improve the coverage of future Keystone
> >>revisions -- hints/patches are welcome. The current ID check is based on
> >>Davinci/Keystone datasheets and is at least working on real Keystone II.
> >
> >+ Murali who works on Keystone devices in TI.
> 
> + Grygorii
> 
> + Grygorii has been involved in the Keystone related enhancement and
> reviewing prior patches. Need to have his ack for this change

Any news?

> 
> Murali
> >
> >>
> >>  drivers/i2c/busses/i2c-davinci.c |   10 ++++++++++
> >>  1 files changed, 10 insertions(+), 0 deletions(-)
> >>
> >>diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
> >>index 4a110af..3d78f6a 100644
> >>--- a/drivers/i2c/busses/i2c-davinci.c
> >>+++ b/drivers/i2c/busses/i2c-davinci.c
> >>@@ -60,6 +60,8 @@
> >>  #define DAVINCI_I2C_IVR_REG	0x28
> >>  #define DAVINCI_I2C_EMDR_REG	0x2c
> >>  #define DAVINCI_I2C_PSC_REG	0x30
> >>+#define DAVINCI_I2C_ICPID1_REG	0x34
> >>+#define DAVINCI_I2C_ICPID2_REG	0x38
> >>  #define DAVINCI_I2C_FUNC_REG	0x48
> >>  #define DAVINCI_I2C_DIR_REG	0x4c
> >>  #define DAVINCI_I2C_DIN_REG	0x50
> >>@@ -203,6 +205,9 @@ static void i2c_davinci_calc_clk_dividers(struct davinci_i2c_dev *dev)
> >>  	 * where if PSC == 0, d = 7,
> >>  	 *       if PSC == 1, d = 6
> >>  	 *       if PSC > 1 , d = 5
> >>+	 *
> >>+	 * Note:
> >>+	 * d is always 6 on Keystone I2C controller
> >>  	 */
> >>
> >>  	/* get minimum of 7 MHz clock, but max of 12 MHz */
> >>@@ -211,6 +216,11 @@ static void i2c_davinci_calc_clk_dividers(struct davinci_i2c_dev *dev)
> >>  		psc++;	/* better to run under spec than over */
> >>  	d = (psc >= 2) ? 5 : 7 - psc;
> >>
> >>+	if (davinci_i2c_read_reg(dev, DAVINCI_I2C_ICPID2_REG) == 0x2206) {
> >>+		dev_dbg(dev->dev, "Keystone SoC detected\n");
> >>+		d = 6;
> >>+	}
> >
> >I think its better to use a different compatible string for i2c on
> >keystone devices rather than using a fixed hardcoded IP version.
> >
> >Thanks,
> >Sekhar
> >
> 
> 
> -- 
> Murali Karicheri
> Linux Kernel, Keystone

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