Re: [PATCH] i3c: master: dw-i3c-master: fix OD timing for first broadcast

On 12/6/2026 12:19 am, Frank Li wrote:
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> 
> On Wed, Jun 10, 2026 at 01:14:26AM -0700, [email protected] wrote:
>> From: Tze Yee Ng <[email protected]>
>>
>> Implement ->set_speed() so the I3C core can switch open-drain timing for
>> the first broadcast address per spec: I3C_OPEN_DRAIN_SLOW_SPEED programs
>> tHIGH_INIT (200 ns) before RSTDAA, and I3C_OPEN_DRAIN_NORMAL_SPEED restores
>> normal OD timing afterward. Cache the normal OD register value during bus
>> init and use a separate od_hcnt for the slow path so SDR extended timing
>> remains derived from the normal PP hcnt.
>>
>> Fixes I2C devices with spike filters not being detected on mixed buses.
>>
>> Signed-off-by: Tze Yee Ng <[email protected]>
>> ---
>>   drivers/i3c/master/dw-i3c-master.c | 53 ++++++++++++++++++++++++++++++
>>   drivers/i3c/master/dw-i3c-master.h |  1 +
>>   include/linux/i3c/master.h         |  1 +
>>   3 files changed, 55 insertions(+)
>>
>> diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c
>> index 655693a2187e..dbb801910b3d 100644
>> --- a/drivers/i3c/master/dw-i3c-master.c
>> +++ b/drivers/i3c/master/dw-i3c-master.c
>> @@ -592,6 +592,7 @@ static int dw_i3c_clk_cfg(struct dw_i3c_master *master)
>>        scl_timing = SCL_I3C_TIMING_HCNT(hcnt) | SCL_I3C_TIMING_LCNT(lcnt);
>>        writel(scl_timing, master->regs + SCL_I3C_OD_TIMING);
>>        master->i3c_od_timing = scl_timing;
>> +     master->i3c_od_timing_normal = scl_timing;
>>
>>        lcnt = DIV_ROUND_UP(core_rate, I3C_BUS_SDR1_SCL_RATE) - hcnt;
>>        scl_timing = SCL_EXT_LCNT_1(lcnt);
>> @@ -1480,6 +1481,57 @@ static irqreturn_t dw_i3c_master_irq_handler(int irq, void *dev_id)
>>        return IRQ_HANDLED;
>>   }
>>
>> +static int dw_i3c_master_set_speed(struct i3c_master_controller *m,
>> +                                enum i3c_open_drain_speed speed)
>> +{
>> +     struct dw_i3c_master *master = to_dw_i3c_master(m);
>> +     unsigned long core_rate, core_period;
>> +     u32 scl_timing;
>> +     u8 od_hcnt, lcnt;
>> +     int ret;
>> +
>> +     ret = pm_runtime_resume_and_get(master->dev);
>> +     if (ret < 0) {
>> +             dev_err(master->dev,
>> +                     "<%s> cannot resume i3c bus master, err: %d\n",
>> +                     __func__, ret);
>> +             return ret;
>> +     }
> 
>          PM_RUNTIME_ACQUIRE_AUTOSUSPEND(dev->dev, pm);
>          if (PM_RUNTIME_ACQUIRE_ERR(&pm))
>                  return -ENXIO;
> 
> Use modem QCQUIRE macro
> 
>> +
>> +     switch (speed) {
>> +     case I3C_OPEN_DRAIN_SLOW_SPEED:
>> +             core_rate = clk_get_rate(master->core_clk);
>> +             if (!core_rate) {
>> +                     ret = -EINVAL;
>> +                     break;
> 
> you can return ret; here after use ACQUIRE macro.
> 
> Frank
>> +             }
>> +
>> +             core_period = DIV_ROUND_UP(1000000000, core_rate);
>> +             lcnt = SCL_I3C_TIMING_LCNT(master->i3c_od_timing_normal);
>> +             od_hcnt = max_t(u8, SCL_I3C_TIMING_CNT_MIN,
>> +                             DIV_ROUND_UP(I3C_BUS_THIGH_INIT_OD_MIN_NS,
>> +                                          core_period) - 1);
>> +             scl_timing = SCL_I3C_TIMING_HCNT(od_hcnt) |
>> +                          SCL_I3C_TIMING_LCNT(lcnt);
>> +             writel(scl_timing, master->regs + SCL_I3C_OD_TIMING);
>> +             master->i3c_od_timing = scl_timing;
>> +             break;
>> +
>> +     case I3C_OPEN_DRAIN_NORMAL_SPEED:
>> +             writel(master->i3c_od_timing_normal,
>> +                    master->regs + SCL_I3C_OD_TIMING);
>> +             master->i3c_od_timing = master->i3c_od_timing_normal;
>> +             break;
>> +
>> +     default:
>> +             ret = -EINVAL;
>> +             break;
>> +     }
>> +     pm_runtime_put_autosuspend(master->dev);
>> +
>> +     return ret;
>> +}
>> +
>>   static int dw_i3c_master_set_dev_nack_retry(struct i3c_master_controller *m,
>>                                            unsigned long dev_nack_retry_cnt)
>>   {
>> @@ -1534,6 +1586,7 @@ static const struct i3c_master_controller_ops dw_mipi_i3c_ops = {
>>        .recycle_ibi_slot = dw_i3c_master_recycle_ibi_slot,
>>        .enable_hotjoin = dw_i3c_master_enable_hotjoin,
>>        .disable_hotjoin = dw_i3c_master_disable_hotjoin,
>> +     .set_speed = dw_i3c_master_set_speed,
>>        .set_dev_nack_retry = dw_i3c_master_set_dev_nack_retry,
>>   };
>>
>> diff --git a/drivers/i3c/master/dw-i3c-master.h b/drivers/i3c/master/dw-i3c-master.h
>> index c5cb695c16ab..c814087a6f1f 100644
>> --- a/drivers/i3c/master/dw-i3c-master.h
>> +++ b/drivers/i3c/master/dw-i3c-master.h
>> @@ -46,6 +46,7 @@ struct dw_i3c_master {
>>        u32 dev_addr;
>>        u32 i3c_pp_timing;
>>        u32 i3c_od_timing;
>> +     u32 i3c_od_timing_normal;
>>        u32 ext_lcnt_timing;
>>        u32 bus_free_timing;
>>        u32 i2c_fm_timing;
>> diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
>> index 592b646f6134..c7d7448c4cd7 100644
>> --- a/include/linux/i3c/master.h
>> +++ b/include/linux/i3c/master.h
>> @@ -259,6 +259,7 @@ struct i3c_device {
>>   #define I3C_BUS_THIGH_MIXED_MAX_NS   41
>>   #define I3C_BUS_TIDLE_MIN_NS         200000
>>   #define I3C_BUS_TLOW_OD_MIN_NS               200
>> +#define I3C_BUS_THIGH_INIT_OD_MIN_NS 200
>>
>>   /**
>>    * enum i3c_bus_mode - I3C bus mode
>> --
>> 2.43.7
>>
Hi Frank,

Thanks for review. I will change to use PM_RUNTIME_ACQUIRE in v2.

Thanks,
Tze Yee
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