Re: [PATCH v5 05/10] coresight-tpda: Add support to configure CMB element

[Suzuki K Poulose <suzuki.poulose@arm.com>]

On 01/02/2024 02:25, Tao Zhang wrote:
> 
> On 1/31/2024 6:02 PM, Suzuki K Poulose wrote:
>> On 31/01/2024 01:39, Tao Zhang wrote:
>>>
>>> On 1/30/2024 8:35 PM, Suzuki K Poulose wrote:
>>>> On 30/01/2024 09:02, Tao Zhang wrote:
>>>>> Read the CMB element size from the device tree. Set the register
>>>>> bit that controls the CMB element size of the corresponding port.
>>>>>
>>>>> Reviewed-by: James Clark <james.clark@arm.com>
>>>>> Signed-off-by: Tao Zhang <quic_taozha@quicinc.com>
>>>>> Signed-off-by: Mao Jinlong <quic_jinlmao@quicinc.com>
>>>>> ---
>>>>>   drivers/hwtracing/coresight/coresight-tpda.c | 123 
>>>>> +++++++++++--------
>>>>>   drivers/hwtracing/coresight/coresight-tpda.h |   6 +
>>>>>   2 files changed, 79 insertions(+), 50 deletions(-)
>>>>>
>>>>> diff --git a/drivers/hwtracing/coresight/coresight-tpda.c 
>>>>> b/drivers/hwtracing/coresight/coresight-tpda.c
>>>>> index 4ac954f4bc13..fcddff3ded81 100644
>>>>> --- a/drivers/hwtracing/coresight/coresight-tpda.c
>>>>> +++ b/drivers/hwtracing/coresight/coresight-tpda.c
>>>>> @@ -18,6 +18,7 @@
>>>>>   #include "coresight-priv.h"
>>>>>   #include "coresight-tpda.h"
>>>>>   #include "coresight-trace-id.h"
>>>>> +#include "coresight-tpdm.h"
>>>>>     DEFINE_CORESIGHT_DEVLIST(tpda_devs, "tpda");
>>>>>   @@ -28,24 +29,57 @@ static bool coresight_device_is_tpdm(struct 
>>>>> coresight_device *csdev)
>>>>>               CORESIGHT_DEV_SUBTYPE_SOURCE_TPDM);
>>>>>   }
>>>>>   +static void tpdm_clear_element_size(struct coresight_device *csdev)
>>>>> +{
>>>>> +    struct tpda_drvdata *drvdata = 
>>>>> dev_get_drvdata(csdev->dev.parent);
>>>>> +
>>>>> +    drvdata->dsb_esize = 0;
>>>>> +    drvdata->cmb_esize = 0;
>>>>> +}
>>>>> +
>>>>> +static void tpda_set_element_size(struct tpda_drvdata *drvdata, 
>>>>> u32 *val)
>>>>> +{
>>>>> +
>>>>
>>>>
>>>>
>>>>> +    if (drvdata->dsb_esize == 64)
>>>>> +        *val |= TPDA_Pn_CR_DSBSIZE;
>>>>
>>>> We don't seem to be clearing the fields we modify, before updating 
>>>> them. This may be OK in real world where the device connected to 
>>>> TPDA port
>>>> may not change. But it is always safer to clear the bits and set it.
>>>>
>>>> e.g.:
>>>>     *val &= ~(TPDA_Pn_CR_DSBSIZE | TPDA_Pn_CR_CMBSIZE);
>>>>
>>>>
>>>>
>>>>> +    else if (drvdata->dsb_esize == 32)
>>>>> +        *val &= ~TPDA_Pn_CR_DSBSIZE;
>>>>> +
>>>>> +    if (drvdata->cmb_esize == 64)
>>>>> +        *val |= FIELD_PREP(TPDA_Pn_CR_CMBSIZE, 0x2);
>>>>> +    else if (drvdata->cmb_esize == 32)
>>>>> +        *val |= FIELD_PREP(TPDA_Pn_CR_CMBSIZE, 0x1);
>>>>
>>>> Similarly here ^^^. I am happy to fix it up if you are OK with it 
>>>> (unless there are other changes that need a respin)
>>>
>>> Thank you. I would be very grateful if you could help for this.
>>
>> Given, you need to respin, please incorporate this change too.
> 
> Sure.
> 
> Is it OK if I modify the code as follow and update to this patch directly?
> 
>      *val &= ~(TPDA_Pn_CR_DSBSIZE | TPDA_Pn_CR_CMBSIZE);
> 
>      if (drvdata->dsb_esize == 64)
>          *val |= TPDA_Pn_CR_DSBSIZE;
>      else if (drvdata->dsb_esize == 32)
>          *val &= ~TPDA_Pn_CR_DSBSIZE;
> 
>      if (drvdata->cmb_esize == 64)
>          *val |= FIELD_PREP(TPDA_Pn_CR_CMBSIZE, 0x2);
>      else if (drvdata->cmb_esize == 32)
>          *val |= FIELD_PREP(TPDA_Pn_CR_CMBSIZE, 0x1);.
>      else if (drvdata->cmb_esize == 8)
>          *val &= ~TPDA_Pn_CR_CMBSIZE;

Yes, that looks good to me. Even though you would be clearing the fields 
for (DSB=32 and CMB=8) once again, it is good to leave it like that 
rather than skipping them, making people stare at it to figure out if 
this was correct or not.

Suzuki




> 
> Best,
> 
> Tao
> 
>>
>> Suzuki
>>
>>
>>