Re: [PATCH 1/2] i3c: Add basic HDR support

[Frank Li <Frank.li@nxp.com>]

On Mon, Feb 03, 2025 at 02:32:51AM +0000, Joshua Yeong wrote:
> Hi Mukesh and Frank,
>
> On 02-Feb-2025 1:54 AM, Mukesh Kumar Savaliya wrote:
> > Hi Frank,
> >
> > On 1/30/2025 1:35 AM, Frank Li wrote:
> >> I3C HDR requires enter/exit patterns during each I3C transfer. Add a new
> >> API i3c_device_do_priv_xfers_mode(). The existing
> >> i3c_device_do_priv_xfers() now calls i3c_device_do_priv_xfers_mode(I3C_SDR)
> >> to maintain backward compatibility.
> >>
> >> Introduce a 'cmd' field in 'struct i3c_priv_xfer', using an anonymous union
> >> with 'rnw' since HDR mode relies on read/write commands instead of the
> >> 'rnw' bit in the address as in SDR mode.
> >>
> >> Add a priv_xfers_mode callback for I3C master drivers. If priv_xfers_mode
> >> is not implemented, fallback to SDR mode using the existing priv_xfers
> >> callback.
> >>
> >> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> >> ---
> >> Why not add hdr mode in struct i3c_priv_xfer because mode can't be mixed in
> >> one i3c transfer. for example, can't send a HDR follow one SDR between
> >> START and STOP.
> >>
> > Is it wise to add two function inside main funcion and separate SDR vs HDR ? so we don't need to change current function arguments.

I am not sure if understand your means. HDR have difference mode, anyway
need add new argument.

>
> I think the 'private transfers' are limited to SDR communications,
> would it be better if we have a different interface/naming for hdr transfers?

The key is what's difference between hdr and private transfers. So far only
command vs rnw, any other differences I missed?

>
> >> i3c_priv_xfer should be treat as whole i3c transactions. If user want send
> >> HDR follow SDR, should be call i3c_device_do_priv_xfers_mode() twice,
> >> instead put into a big i3c_priv_xfer[n].
> >> ---
> >>   drivers/i3c/device.c       | 19 +++++++++++++------
> >>   drivers/i3c/internals.h    |  2 +-
> >>   drivers/i3c/master.c       |  8 +++++++-
> >>   include/linux/i3c/device.h | 12 +++++++++++-
> >>   include/linux/i3c/master.h |  3 +++
> >>   5 files changed, 35 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/drivers/i3c/device.c b/drivers/i3c/device.c
> >> index e80e487569146..e3db3a6a9e4f6 100644
> >> --- a/drivers/i3c/device.c
> >> +++ b/drivers/i3c/device.c
> >> @@ -15,12 +15,13 @@
> >>   #include "internals.h"
> >>     /**
> >> - * i3c_device_do_priv_xfers() - do I3C SDR private transfers directed to a
> >> - *                specific device
> >> + * i3c_device_do_priv_xfers_mode() - do I3C SDR private transfers directed to a
> >> + *                     specific device
> >>    *
> >>    * @dev: device with which the transfers should be done
> >>    * @xfers: array of transfers
> >>    * @nxfers: number of transfers
> >> + * @mode: transfer mode
> >>    *
> >>    * Initiate one or several private SDR transfers with @dev.
> >>    *
> >> @@ -32,9 +33,9 @@
> >>    *            driver needs to resend the 'xfers' some time later.
> >>    *            See I3C spec ver 1.1.1 09-Jun-2021. Section: 5.1.2.2.3.
> >>    */
> >> -int i3c_device_do_priv_xfers(struct i3c_device *dev,
> >> -                 struct i3c_priv_xfer *xfers,
> >> -                 int nxfers)
> >> +int i3c_device_do_priv_xfers_mode(struct i3c_device *dev,
> >> +                  struct i3c_priv_xfer *xfers,
> >> +                  int nxfers, enum i3c_hdr_mode mode)
> > why can't we pass mode as another structure member inside struct i3c_priv_xfer ? Adding function agrument parameter impacts existing drivers.

If that, it will be possible, xfers[0] is sdr, xfers[1] is hdr. Actually,
I3C can't do that.  we assume finish whole xfers between one whole traction
(between START and STOP).

Frank
> >>   {
> >>       int ret, i;
> >>   @@ -47,11 +48,17 @@ int i3c_device_do_priv_xfers(struct i3c_device *dev,
> >>       }
> >>         i3c_bus_normaluse_lock(dev->bus);
> >> -    ret = i3c_dev_do_priv_xfers_locked(dev->desc, xfers, nxfers);
> >> +    ret = i3c_dev_do_priv_xfers_locked(dev->desc, xfers, nxfers, mode);
> >>       i3c_bus_normaluse_unlock(dev->bus);
> >>         return ret;
> >>   }
> >> +EXPORT_SYMBOL_GPL(i3c_device_do_priv_xfers_mode);
> >> +
> >> +int i3c_device_do_priv_xfers(struct i3c_device *dev, struct i3c_priv_xfer *xfers, int nxfers)
> >> +{
> >> +    return i3c_device_do_priv_xfers_mode(dev, xfers, nxfers, I3C_SDR);
> >> +}
> >>   EXPORT_SYMBOL_GPL(i3c_device_do_priv_xfers);
> >>     /**
> >> diff --git a/drivers/i3c/internals.h b/drivers/i3c/internals.h
> >> index 433f6088b7cec..553edc9846ac0 100644
> >> --- a/drivers/i3c/internals.h
> >> +++ b/drivers/i3c/internals.h
> >> @@ -16,7 +16,7 @@ void i3c_bus_normaluse_unlock(struct i3c_bus *bus);
> >>   int i3c_dev_setdasa_locked(struct i3c_dev_desc *dev);
> >>   int i3c_dev_do_priv_xfers_locked(struct i3c_dev_desc *dev,
> >>                    struct i3c_priv_xfer *xfers,
> >> -                 int nxfers);
> >> +                 int nxfers, enum i3c_hdr_mode mode);
> >>   int i3c_dev_disable_ibi_locked(struct i3c_dev_desc *dev);
> >>   int i3c_dev_enable_ibi_locked(struct i3c_dev_desc *dev);
> >>   int i3c_dev_request_ibi_locked(struct i3c_dev_desc *dev,
> >> diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
> >> index d5dc4180afbcf..67aaba0a38db2 100644
> >> --- a/drivers/i3c/master.c
> >> +++ b/drivers/i3c/master.c
> >> @@ -2945,7 +2945,7 @@ int i3c_dev_setdasa_locked(struct i3c_dev_desc *dev)
> >>     int i3c_dev_do_priv_xfers_locked(struct i3c_dev_desc *dev,
> >>                    struct i3c_priv_xfer *xfers,
> >> -                 int nxfers)
> >> +                 int nxfers, enum i3c_hdr_mode mode)
> >>   {
> >>       struct i3c_master_controller *master;
> >>   @@ -2956,9 +2956,15 @@ int i3c_dev_do_priv_xfers_locked(struct i3c_dev_desc *dev,
> >>       if (!master || !xfers)
> >>           return -EINVAL;
> >>   +    if (master->ops->priv_xfers_mode)
> >> +        return master->ops->priv_xfers_mode(dev, xfers, nxfers, mode);
> >> +
> >>       if (!master->ops->priv_xfers)
> >>           return -ENOTSUPP;
> >>   +    if (mode != I3C_SDR)
> >> +        return -EINVAL;
> >> +
> >>       return master->ops->priv_xfers(dev, xfers, nxfers);
> >>   }
> >>   diff --git a/include/linux/i3c/device.h b/include/linux/i3c/device.h
> >> index b674f64d0822e..7ce70d0967e27 100644
> >> --- a/include/linux/i3c/device.h
> >> +++ b/include/linux/i3c/device.h
> >> @@ -40,11 +40,13 @@ enum i3c_error_code {
> >>     /**
> >>    * enum i3c_hdr_mode - HDR mode ids
> >> + * @I3C_SDR: SDR mode (NOT HDR mode)
> >>    * @I3C_HDR_DDR: DDR mode
> >>    * @I3C_HDR_TSP: TSP mode
> >>    * @I3C_HDR_TSL: TSL mode
> >>    */
> >>   enum i3c_hdr_mode {
> >> +    I3C_SDR,
> >>       I3C_HDR_DDR,
> >>       I3C_HDR_TSP,
> >>       I3C_HDR_TSL,
> >> @@ -53,6 +55,7 @@ enum i3c_hdr_mode {
> >>   /**
> >>    * struct i3c_priv_xfer - I3C SDR private transfer
> >>    * @rnw: encodes the transfer direction. true for a read, false for a write
> >> + * @cmd: Read/Write command in HDR mode, read: 0x80 - 0xff, write: 0x00 - 0x7f
> >>    * @len: transfer length in bytes of the transfer
> >>    * @actual_len: actual length in bytes are transferred by the controller
> >>    * @data: input/output buffer
> >> @@ -61,7 +64,10 @@ enum i3c_hdr_mode {
> >>    * @err: I3C error code
> >>    */
> >>   struct i3c_priv_xfer {
> >> -    u8 rnw;
> >> +    union {
> >> +        u8 rnw;
> >> +        u8 cmd;
> >> +    };
> >>       u16 len;
> >>       u16 actual_len;
> >>       union {
> >> @@ -301,6 +307,10 @@ int i3c_device_do_priv_xfers(struct i3c_device *dev,
> >>                    struct i3c_priv_xfer *xfers,
> >>                    int nxfers);
> >>   +int i3c_device_do_priv_xfers_mode(struct i3c_device *dev,
> >> +                  struct i3c_priv_xfer *xfers,
> >> +                  int nxfers, enum i3c_hdr_mode mode);
> >> +
> >>   int i3c_device_do_setdasa(struct i3c_device *dev);
> >>     void i3c_device_get_info(const struct i3c_device *dev, struct i3c_device_info *info);
> >> diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
> >> index 12d532b012c5a..352bd41139569 100644
> >> --- a/include/linux/i3c/master.h
> >> +++ b/include/linux/i3c/master.h
> >> @@ -472,6 +472,9 @@ struct i3c_master_controller_ops {
> >>       int (*priv_xfers)(struct i3c_dev_desc *dev,
> >>                 struct i3c_priv_xfer *xfers,
> >>                 int nxfers);
> >> +    int (*priv_xfers_mode)(struct i3c_dev_desc *dev,
> >> +                   struct i3c_priv_xfer *xfers,
> >> +                   int nxfers, enum i3c_hdr_mode mode);
> >>       int (*attach_i2c_dev)(struct i2c_dev_desc *dev);
> >>       void (*detach_i2c_dev)(struct i2c_dev_desc *dev);
> >>       int (*i2c_xfers)(struct i2c_dev_desc *dev,
> >>
> >
> >
>