Re: [PATCH v2 2/3] i2c: xilinx: Set tx direction in write operation

[Michal Simek <monstr-pSz03upnqPeHXe+LvDLADg@public.gmane.org>]

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On 10/04/2013 07:46 AM, Wolfram Sang wrote:
> 
>> +	cr = xiic_getreg32(i2c, XIIC_CR_REG_OFFSET);
>> +	cr |= XIIC_CR_DIR_IS_TX_MASK;
>> +	xiic_setreg32(i2c, XIIC_CR_REG_OFFSET, cr);
>> +
> 
> Is there no need to clear the bit again when receiving?

This bit is cleared in xiic_xfer() -> xiic_start_xfer() ->xiic_reinit()

xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, XIIC_CR_TX_FIFO_RESET_MASK);


> And did
> transferring ever work if this bit was never set before?

I really don't know. We have switched from old driver to this new mainline one
and based on our eeprom testing we have found that this bit hasn't been setup properly.

It is described here.
http://www.xilinx.com/support/documentation/ip_documentation/axi_iic/v1_02_a/axi_iic_ds756.pdf
page 28 - step 3.

IIC Master Transmitter with a Repeated Start
1. Write the IIC device address to the TX_FIFO.
2. Write data to TX_FIFO.
3. Write to Control Register (CR) to set MSMS = 1 and TX = 1.
4. Continue writing data to TX_FIFO.
5. Wait for transmit FIFO empty interrupt. This implies the IIC has throttled the bus.
6. Write to CR to set RSTA = 1.
7. Write IIC device address to TX_FIFO.
8. Write all data except last byte to TX_FIFO.
9. Wait for transmit FIFO empty interrupt. This implies the IIC has throttled the bus.
10. Write to CR to set MSMS = 0. The IIC generates a stop condition at the end of the last byte.
11. Write last byte of data to TX_FIFO.

Thanks,
Michal


-- 
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
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Maintainer of Linux kernel - Microblaze cpu - http://www.monstr.eu/fdt/
Maintainer of Linux kernel - Xilinx Zynq ARM architecture
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