Re: [PATCH v8 2/4] coresight: cti: encode trigger register index in register offsets

[Leo Yan <leo.yan@arm.com>]

On Sun, Apr 26, 2026 at 05:44:39PM +0800, Yingchao Deng wrote:
> Introduce a small encoding to carry the register index together with the
> base offset in a single u32, and use a common helper to compute the final
> MMIO address. This refactors register access to be based on the encoded
> (reg, nr) pair, reducing duplicated arithmetic and making it easier to
> support variants that bank or relocate trigger-indexed registers.
> 
> Signed-off-by: Yingchao Deng <yingchao.deng@oss.qualcomm.com>
> ---
>  drivers/hwtracing/coresight/coresight-cti-core.c  | 31 +++++++++++++++--------
>  drivers/hwtracing/coresight/coresight-cti-sysfs.c |  4 +--
>  drivers/hwtracing/coresight/coresight-cti.h       | 16 ++++++++++--
>  3 files changed, 36 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-cti-core.c b/drivers/hwtracing/coresight/coresight-cti-core.c
> index 4e7d12bd2d3e..c4cbeb64365b 100644
> --- a/drivers/hwtracing/coresight/coresight-cti-core.c
> +++ b/drivers/hwtracing/coresight/coresight-cti-core.c
> @@ -42,6 +42,14 @@ static DEFINE_MUTEX(ect_mutex);
>  #define csdev_to_cti_drvdata(csdev)	\
>  	dev_get_drvdata(csdev->dev.parent)
>  
> +static void __iomem *cti_reg_addr(struct cti_drvdata *drvdata, int reg)
> +{
> +	u32 offset = CTI_REG_CLR_NR(reg);
> +	u32 nr = CTI_REG_GET_NR(reg);
> +
> +	return drvdata->base + offset + sizeof(u32) * nr;
> +}

Could you try below change, which is more straightforward?

  static void __iomem *__reg_addr(struct cti_drvdata *drvdata, int off,
                                  int index)
  {
  	return drvdata->base + offset + sizeof(u32) * index;
  }

  #define reg_addr(drvdata, off)                 \
        __reg_addr((drvdata), (off), 0)

  #define reg_index_addr(drvdata, off, i)        \
        __reg_addr((drvdata), (off), (i))

> +
>  /* write set of regs to hardware - call with spinlock claimed */
>  void cti_write_all_hw_regs(struct cti_drvdata *drvdata)
>  {
> @@ -55,16 +63,17 @@ void cti_write_all_hw_regs(struct cti_drvdata *drvdata)
>  
>  	/* write the CTI trigger registers */
>  	for (i = 0; i < config->nr_trig_max; i++) {
> -		writel_relaxed(config->ctiinen[i], drvdata->base + CTIINEN(i));
> +		writel_relaxed(config->ctiinen[i],
> +			       cti_reg_addr(drvdata, CTI_REG_SET_NR(CTIINEN, i)));

                writel_relaxed(config->ctiinen[i],
                               reg_index_addr(drvdata, CTIINEN, i));

>  		writel_relaxed(config->ctiouten[i],
> -			       drvdata->base + CTIOUTEN(i));
> +			       cti_reg_addr(drvdata, CTI_REG_SET_NR(CTIOUTEN, i)));

                writel_relaxed(config->ctiouten[i],
                               reg_index_addr(drvdata, CTIOUTEN, i));

[...]

> +/*
> + * Encode CTI register offset and register index in one u32:
> + *   - bits[0:11]  : base register offset (0x000 to 0xFFF)
> + *   - bits[24:31] : register index (nr)
> + */
> +#define CTI_REG_NR_MASK			GENMASK(31, 24)
> +#define CTI_REG_GET_NR(reg)		FIELD_GET(CTI_REG_NR_MASK, (reg))
> +#define CTI_REG_SET_NR_CONST(reg, nr)	((reg) | FIELD_PREP_CONST(CTI_REG_NR_MASK, (nr)))
> +#define CTI_REG_SET_NR(reg, nr)		((reg) | FIELD_PREP(CTI_REG_NR_MASK, (nr)))
> +#define CTI_REG_CLR_NR(reg)		((reg) & (~CTI_REG_NR_MASK))

I know this might come from my suggestion, and it is also will be
heavily used in patch 04.  We can have strightforward way to
implement this, please drop these macros.

I will reply in patch 04 separately.  Sorry my review might cause
extra effort.

Thanks,
Leo