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

From: Frank Li
Date: Thu Feb 06 2025 - 10:55:55 EST

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In reply to: Joshua Yeong: "Re: [PATCH 1/2] i3c: Add basic HDR support"
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On Thu, Feb 06, 2025 at 07:05:03AM +0000, Joshua Yeong wrote:
> On 05-Feb-2025 11:58 PM, Frank Li wrote:
> > On Wed, Feb 05, 2025 at 06:30:49AM +0000, Joshua Yeong wrote:
> >> On 04-Feb-2025 11:38 PM, Frank Li wrote:
> >>> On Tue, Feb 04, 2025 at 03:17:36AM +0000, Joshua Yeong wrote:
> >>>> Hi Frank,
> >>>>
> >>>> On 03-Feb-2025 11:52 PM, Frank Li wrote:
> >>>>> 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@xxxxxxx>
> >>>>>>>> ---
> >>>>>>>> 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?
> >>>>
> >>>> I guess mainly the terminology. The specification differentiate HDR from private transfer.
> >>>> We can have the hdr interface to have length indicating for u16 rather than u8 in private trasnfer.
> >>>
> >>> It should be equivalence with check length is even.
> >>>
> >>> The key is how client driver will easy to use HDR if they already have SDR
> >>> support.
> >>>
> >>> suppose client:
> >>>
> >>> struct i3c_priv_xfer xfer[2] = {{ .rnw = 0, buf=p1, size = 4, addr=0xb },
> >>> { .rnw = 1, buf=p2, size = 4, addr=0xb }}
> >>>
> >>> priv_xfer(..., xfer, 2};
> >>>
> >>> if support HDR
> >>>
> >>> if (hdr) {
> >>> xfer[0].cmd = 0x80;
> >>> xfer[1].cmd = 0x;
> >>> priv_xfer(..., xfer, 2, HDR);
> >>> } else {
> >>> priv_xfer(..., xfer, 2, SDR);
> >>> }
> >>>
> >>> client driver needn't distingiush if buff is u8* or u16*.
> >>>
> >>
> >> I fine with the overall structure `.rnw`, `buf`, `size` and `addr`.
> >>
> >> I prefer if we could use `hdr_xfer` rather than `priv_xfer` for HDR transfer and we can have
> >> distinguish mode for DDR/TSP/TSL/BT. In case we are supporting for ML in the future
> >
> > what's means of "ML"?
> >
> >> we dont have to lump the function into `priv_xfer`, and we can go `ml_xfer` instead.
> >
> > Actually, you suggest, rename 'i3c_device_do_priv_xfers_mode' to
> > 'i3c_device_ml_xfer'?
> >
>
> So there are 3 types of I3C Protocol as defined in I3C spec v1.1.1.
> Single Data Rate (SDR), High Data Rate (HDR) and Multi-lane (ML).
> I suggest to kept the existing priv_xfers for SDR transfer only.
> The MIPI I3C specification only uses private transfer for SDR.
>
> I assume not all I3C IP vendor support HDR mode, but they should at least support SDR mode.
> We should have another set of API that uses `i3c_device_do_hdr_xfers`.
> `priv_xfer` should represent private transfer and the keyword private keyword
> here are unique keyword itself should not mix up with HDR.
> Unless the I3C specs stated otherwise I dont think we should mixed up here.
>
> Also interface for sdr/hdr should resolve the other ongoing discussion thread
> where mixing both sdr and hdr in `priv_xfer`

What's you perfer 'struct hdr_xfer'? I read spec, according to line 8703,
Just reduce scl clock number when transfer data, which should be transparent
to software.

Frank

>
> Joshua
>
> >>
> >> The issue with length indicating both u8 and u16 here is that we would get confuse how the
> >> buffer length is interpreted, when length is 1 does it mean 2 bytes or 1 byte? Splitting HDR
> >> interface will ensure that length always indicate u16.
> >
> > All data transfers should be defined in terms of bytes or block units. Note
> > that QSPI DDR mode faces a similar constraint, supporting only even-length
> > transfers. In most systems, alignment requirements are used to indicate
> > size constraints:
> >
> > SDR mode: Alignment is 1 byte.
> > HDR mode: Alignment is 2 bytes.
> >
> > When using DMA without a bounce buffer, the alignment must match the cache
> > line size. Changing to a u16 type does not provide enough flexibility.
> > Instead, I propose using a void* (or u8*) for the buffer and a byte count
> > for the size. This approach allows for more extensible alignment
> > requirements and better compatibility with other transfer systems, such as
> > SPI and PCIe.
> >
> > Frank
> >>
> >> Joshua
> >>
> >>
> >>>> I think the framework should check if device whether it supports HDR command before sending it.
> >>>> I have code here that do some handling on that.
> >>>
> >>> Yes, I can add such check. The key point is API design.
> >>>
> >>> Frank
> >>>>
> >>>>>
> >>>>>>
> >>>>>>>> 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
> >>>>
> >>>> Yes, I think it is better if we split xfer transfer interface for SDR and HDR.
> >>>> The interface should assume respective driver to decide how to handle ENTHDR CCC + Exit Pattern.
> >>>> Else we will need additional 2 interface for start and stop for HDR.
> >>>>
> >>>> Joshua
> >>>>
> >>>>
> >>>>>>>> {
> >>>>>>>>       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,
> >>>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>
> >>>>
> >>
> >> --
> >> linux-i3c mailing list
> >> linux-i3c@xxxxxxxxxxxxxxxxxxx
> >> http://lists.infradead.org/mailman/listinfo/linux-i3c
>
> --
> linux-i3c mailing list
> linux-i3c@xxxxxxxxxxxxxxxxxxx
> http://lists.infradead.org/mailman/listinfo/linux-i3c

Next message: Luck, Tony: "RE: [PATCH v11 10/23] x86/resctrl: Remove MSR reading of event configuration value"
Previous message: Miguel Ojeda: "Re: [PATCH] Add -fzero-init-padding-bits to bindgen_skip_cflags"
In reply to: Joshua Yeong: "Re: [PATCH 1/2] i3c: Add basic HDR support"
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