[AMD Official Use Only - General]
> -----Original Message-----
> From: Simek, Michal <michal.simek@xxxxxxx>
> Sent: Monday, July 18, 2022 2:56 PM
> To: Lars-Peter Clausen <lars@xxxxxxxxxx>; Wolfram Sang
> <wsa@xxxxxxxxxx>; Datta, Shubhrajyoti <shubhrajyoti.datta@xxxxxxx>
> Cc: linux-i2c@xxxxxxxxxxxxxxx; git <git@xxxxxxxxxx>
> Subject: Re: [PATCH] i2c: cadence: Support PEC for SMBus block read
>
>
>
> On 7/17/22 16:52, Lars-Peter Clausen wrote:
> > SMBus packet error checking (PEC) is implemented by appending one
> > additional byte of checksum data at the end of the message. This
> > provides additional protection and allows to detect data corruption on the
> I2C bus.
> >
> > SMBus block reads support variable length reads. The first byte in the
> > read message is the number of available data bytes.
> >
> > The combination of PEC and block read is currently not supported by
> > the Cadence I2C driver.
> > * When PEC is enabled the maximum transfer length for block reads
> > increases from 33 to 34 bytes.
> > * The I2C core smbus emulation layer relies on the driver updating the
> > `i2c_msg` `len` field with the number of received bytes. The updated
> > length is used when checking the PEC.
> >
> > Add support to the Cadence I2C driver for handling SMBus block reads
> > with PEC. To determine the maximum transfer length uses the initial
> > `len` value of the `i2c_msg`. When PEC is enabled this will be 2, when
> > it is disabled it will be 1.
> >
> > Once a read transfer is done also increment the `len` field by the
> > amount of received data bytes.
> >
> > This change has been tested with a UCM90320 PMBus power monitor,
> which
> > requires block reads to access certain data fields, but also has PEC
> > enabled by default.
> >
> > Fixes: df8eb5691c48 ("i2c: Add driver for Cadence I2C controller")
>
> Subject is saying that you adding support for PEC and here you are saying
> that it is fixing initial commit.
>
> If this is adding new support I think Fixes tag shouldn't be here.
>
> If it is fixing issue subject should be updated and this Fixes tag kept here.
>
> The rest looks good to me.
>
> Shubhrajyoti: Can you please test?
I have tested the reads and write smbus without packet error check.
>
> Thanks,
> Michal
