linux-kernel - Re: [EXT] Re: [v10] i2c: imx: support slave mode for imx I2C driver

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Date:   Fri, 11 Dec 2020 09:57:19 -0800
From:   Kevin Herbert <kph@...tinasystems.com>
To:     Biwen Li <biwen.li@....com>
Cc:     Wolfram Sang <wsa@...-dreams.de>,
        "Biwen Li (OSS)" <biwen.li@....nxp.com>,
        Leo Li <leoyang.li@....com>,
        "linux@...pel-privat.de" <linux@...pel-privat.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        Aisheng Dong <aisheng.dong@....com>,
        Clark Wang <xiaoning.wang@....com>,
        "o.rempel@...gutronix.de" <o.rempel@...gutronix.de>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jiafei Pan <jiafei.pan@....com>,
        Xiaobo Xie <xiaobo.xie@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [EXT] Re: [v10] i2c: imx: support slave mode for imx I2C driver

Thanks for the tip. I attempted to see if the register was implemented
on the i.mx6, and it doesn't appear to be. I'll reach out to my FAE. I
found the datasheet and the register definitely isn't documented
there.

I was thinking of a patch that would keep track of state, and
synthesize the I2C_SLAVE_STOP on the next interrupt if it was a new
transaction. Does this seem too hacky to you? What are your thoughts?

Thanks,
Kevin

Thanks,
Kevin


On Wed, Dec 9, 2020 at 6:16 PM Biwen Li <biwen.li@....com> wrote:
>
> Hi Kevin,
>
>
>
> After enabling idle interrupts, the i2c register will generate an idle interrupts(whatever read or write) when i2c bus enter idle status. Then get I2C_SLAVE_STOP event.
>
> But don’t have the IBIC register(Maybe it’s a hidden register) in imx. You can query about the AE of imx about this.
>
> static void i2c_imx_enable_bus_idle(struct imx_i2c_struct *i2c_imx)
>
> {
>
>         if (is_vf610_i2c(i2c_imx)) {
>
>                 unsigned int temp;
>
>
>
>                 temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_IBIC);
>
>                 temp |= IBIC_BIIE;
>
>                 imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_IBIC);
>
>         }
>
> }
>
>
>
> Best Regards,
>
> Biwen Li
>
> From: Kevin Herbert <kph@...tinasystems.com>
> Sent: 2020年12月10日 1:18
> To: Wolfram Sang <wsa@...-dreams.de>; Kevin Herbert <kph@...tinasystems.com>; Biwen Li (OSS) <biwen.li@....nxp.com>; Leo Li <leoyang.li@....com>; linux@...pel-privat.de; kernel@...gutronix.de; shawnguo@...nel.org; s.hauer@...gutronix.de; festevam@...il.com; Aisheng Dong <aisheng.dong@....com>; Clark Wang <xiaoning.wang@....com>; o.rempel@...gutronix.de; linux-i2c@...r.kernel.org; linux-kernel@...r.kernel.org; Jiafei Pan <jiafei.pan@....com>; Xiaobo Xie <xiaobo.xie@....com>; linux-arm-kernel@...ts.infradead.org; Biwen Li <biwen.li@....com>
> Subject: [EXT] Re: [v10] i2c: imx: support slave mode for imx I2C driver
>
>
>
> Caution: EXT Email
>
> Even on an operation like writing a byte, I get I2C_SLAVE_WRITE_REQUESTED followed by I2C_SLAVE_WRITE_RECEIVED, but no I2C_SLAVE_STOP. If I do a I2C write of multiple bytes, I get I2c_SLAVE_WRITE_REQUESTED followed by multiple I2C_SLAVE_WRITE_RECEIVED.
>
>
>
> Kevin
>
>
>
> On Wed, Dec 9, 2020 at 9:10 AM Wolfram Sang <wsa@...-dreams.de> wrote:
>
> On Wed, Dec 09, 2020 at 09:03:50AM -0800, Kevin Herbert wrote:
> > What is the protocol for the I2C_SLAVE_STOP event? I am working on my own
> > backend, and I've only tried it with this i.mx driver, and I do not receive
> > I2C_SLAVE_STOP at the end of every I2C transaction. It was my expectation
> > I'd receive this event at the end of every frame. In my testing, I've never
> > received this event at all.
> >
> > Where are the I2C registers on the i.mx documented? My board is an i.mx6sx.
>
> Hmm, from a glimpse, it looks the STOP event is only sent after a write
> and not after a read? Does this match your findings?