Re: [PATCH 01/15] coresight: Make ETM4x TRCIDR0 register accesses consistent with sysreg.h

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

Hi James

Thanks for taking this tedious task of cleaning the code and making
this robust and readable.

One minor comment below.

On 02/02/2022 16:02, James Clark wrote:
> This is a no-op change for style and consistency and has no effect on the
> binary produced by gcc-11.
> 
> Signed-off-by: James Clark <james.clark@arm.com>
> ---
>   .../coresight/coresight-etm4x-core.c          | 37 +++++--------------
>   drivers/hwtracing/coresight/coresight-etm4x.h | 17 +++++++++
>   drivers/hwtracing/coresight/coresight-priv.h  |  1 +
>   3 files changed, 27 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> index bf18128cf5de..8aefee4e72fd 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> @@ -1091,41 +1091,22 @@ static void etm4_init_arch_data(void *info)
>   	etmidr0 = etm4x_relaxed_read32(csa, TRCIDR0);
>   
>   	/* INSTP0, bits[2:1] P0 tracing support field */
> -	if (BMVAL(etmidr0, 1, 1) && BMVAL(etmidr0, 2, 2))
> -		drvdata->instrp0 = true;
> -	else
> -		drvdata->instrp0 = false;
> -
> +	drvdata->instrp0 = !!((REG_VAL(etmidr0, TRCIDR0_INSTP0) & 0b01) &&
> +			      (REG_VAL(etmidr0, TRCIDR0_INSTP0) & 0b10));

I don't understand this check. For ETMv4, here is what I find in the 
spec (ARM IHI 0064C)

P0 tracing support field. The permitted values are:
0b00  Tracing of load and store instructions as P0 elements is not
       supported.
0b11  Tracing of load and store instructions as P0 elements is
       supported, so TRCCONFIGR.INSTP0 is supported.

All other values are reserved.

So the check could simply be :

	drvdata->instrp0 = (REG_VAL(emtidr0, TRCIDR0_INSTP0) == 0b11;

That said, I think this is all dead code on ETMv4 as we never support
data tracing on A class. May be there will be a use with R class in the
future.


>   	/* TRCBB, bit[5] Branch broadcast tracing support bit */
> -	if (BMVAL(etmidr0, 5, 5))
> -		drvdata->trcbb = true;
> -	else
> -		drvdata->trcbb = false;
> -
> +	drvdata->trcbb = !!(etmidr0 & TRCIDR0_TRCBB);
>   	/* TRCCOND, bit[6] Conditional instruction tracing support bit */
> -	if (BMVAL(etmidr0, 6, 6))
> -		drvdata->trccond = true;
> -	else
> -		drvdata->trccond = false;
> -
> +	drvdata->trccond = !!(etmidr0 & TRCIDR0_TRCCOND);
>   	/* TRCCCI, bit[7] Cycle counting instruction bit */
> -	if (BMVAL(etmidr0, 7, 7))
> -		drvdata->trccci = true;
> -	else
> -		drvdata->trccci = false;
> -
> +	drvdata->trccci = !!(etmidr0 & TRCIDR0_TRCCCI);
>   	/* RETSTACK, bit[9] Return stack bit */
> -	if (BMVAL(etmidr0, 9, 9))
> -		drvdata->retstack = true;
> -	else
> -		drvdata->retstack = false;
> -
> +	drvdata->retstack = !!(etmidr0 & TRCIDR0_RETSTACK);
>   	/* NUMEVENT, bits[11:10] Number of events field */
> -	drvdata->nr_event = BMVAL(etmidr0, 10, 11);
> +	drvdata->nr_event = REG_VAL(etmidr0, TRCIDR0_NUMEVENT);
>   	/* QSUPP, bits[16:15] Q element support field */
> -	drvdata->q_support = BMVAL(etmidr0, 15, 16);
> +	drvdata->q_support = REG_VAL(etmidr0, TRCIDR0_QSUPP);
>   	/* TSSIZE, bits[28:24] Global timestamp size field */
> -	drvdata->ts_size = BMVAL(etmidr0, 24, 28);
> +	drvdata->ts_size = REG_VAL(etmidr0, TRCIDR0_TSSIZE);
>   
>   	/* maximum size of resources */
>   	etmidr2 = etm4x_relaxed_read32(csa, TRCIDR2);
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
> index 3c4d69b096ca..2bd8ad953b8e 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.h
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.h
> @@ -130,6 +130,23 @@
>   
>   #define TRCRSR_TA			BIT(12)
>   
> +/*
> + * Bit positions of registers that are defined above, in the sysreg.h style
> + * of _MASK, _SHIFT and BIT().
> + */
> +#define TRCIDR0_INSTP0_SHIFT			1
> +#define TRCIDR0_INSTP0_MASK			GENMASK(1, 0)
> +#define TRCIDR0_TRCBB				BIT(5)
> +#define TRCIDR0_TRCCOND				BIT(6)
> +#define TRCIDR0_TRCCCI				BIT(7)
> +#define TRCIDR0_RETSTACK			BIT(9)
> +#define TRCIDR0_NUMEVENT_SHIFT			10
> +#define TRCIDR0_NUMEVENT_MASK			GENMASK(1, 0)
> +#define TRCIDR0_QSUPP_SHIFT			15
> +#define TRCIDR0_QSUPP_MASK			GENMASK(1, 0)
> +#define TRCIDR0_TSSIZE_SHIFT			24
> +#define TRCIDR0_TSSIZE_MASK			GENMASK(4, 0)
> +

Cross checked the spec, and they look correct.

>   /*
>    * System instructions to access ETM registers.
>    * See ETMv4.4 spec ARM IHI0064F section 4.3.6 System instructions
> diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
> index ff1dd2092ac5..e22fa6184c6d 100644
> --- a/drivers/hwtracing/coresight/coresight-priv.h
> +++ b/drivers/hwtracing/coresight/coresight-priv.h
> @@ -36,6 +36,7 @@
>   
>   #define TIMEOUT_US		100
>   #define BMVAL(val, lsb, msb)	((val & GENMASK(msb, lsb)) >> lsb)
> +#define REG_VAL(val, name)	((val & (name##_MASK << name##_SHIFT)) >> name##_SHIFT)

super minor nit: s/name/field ?

>   
>   #define ETM_MODE_EXCL_KERN	BIT(30)
>   #define ETM_MODE_EXCL_USER	BIT(31)