From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marek Vasut <marex-ynQEQJNshbs@public.gmane.org>
Subject: Re: [PATCH V2 2/3] i2c: mxs: Rework the PIO mode operation
Date: Sun, 25 Aug 2013 18:19:57 +0200
Message-ID: <201308251819.57351.marex@denx.de>
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To: Torsten Fleischer <to-fleischer-zqRNUXuvxA0b1SvskN2V4Q@public.gmane.org>
Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Alexandre Belloni <alexandre.belloni-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>, Christoph Baumann <cb-/RsSufbtIHM@public.gmane.org>, Fabio Estevam <r49496-KZfg59tc24xl57MIdRCFDg@public.gmane.org>, Shawn Guo <shawn.guo-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
List-Id: linux-i2c@vger.kernel.org

Dear Torsten Fleischer,

> Hi Marek,
> 
> > +
> > +			mxs_i2c_pio_trigger_write_cmd(i2c,
> > +				start | MXS_I2C_CTRL0_MASTER_MODE |
> > +				MXS_I2C_CTRL0_DIRECTION |
> > +				MXS_I2C_CTRL0_XFER_COUNT(xlen), data);
> > +
> > +			/* The START condition is sent only once. */
> > +			start &= ~MXS_I2C_CTRL0_PRE_SEND_START;
> > +
> > +			/* Wait for the end of the transfer. */
> > +			ret = mxs_i2c_pio_wait_xfer_end(i2c);
> > +			if (ret) {
> > +				dev_err(i2c->dev,
> > +					"PIO: Failed to finish WRITE cmd!\n");
> > +				break;
> > +			}
> > +
> > +			/* Check NAK here ? */
> 
> checking for the NAK at this point is really necessary.
> 
> I've tested the patches by writing to the EEPROM using the at24 driver.
> If the data to write cross the EEPROM's page boundary then the at24 driver
> splits the I2C write commands.
> 
> After the first I2C write command is done the at24 driver immediately tries
> to send the next I2C write command. Normally the EEPROM signals a NAK,
> because the previous write operation is internally still in progress. The
> NAK will be handled by the at24 driver. It later retries the I2C write
> command.
> 
> But if the the EEPROM signals a NAK and the I2C write command has more than
> 3 and less than 7 bytes then the error "PIO: Failed to finish WRITE cmd!"
> appears, because the loop is not exited due to the NAK.

Ok, so we check

HW_I2C_STAT :: GOT_A_NAK bit at the end of the loop and if it's set, we "goto 
cleanup" with ret = -ENXIO . How does it sound to you? Wolfram, is -ENXIO the 
right one here?

Best regards,
Marek Vasut