Re: [PATCH v5 04/12] coresight: etm4x: exclude ss_status from drvdata->config

Jie Gan
2026-04-16T05:42:47Z

On 4/16/2026 12:55 AM, Yeoreum Yun wrote:
> The purpose of TRCSSCSRn register is to show status of
> the corresponding Single-shot Comparator Control and input supports.
> That means writable field's purpose for reset or restore from idle status
> not for configuration.
>
> Therefore, exclude ss_status from drvdata->config, move it to etm4x_caps
> and rename it to ss_smp.
>
> This includes remove TRCSSCRn from configurable item and
> remove saving in etm4_disable_hw().
>
> Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
> ---
> .../hwtracing/coresight/coresight-etm4x-cfg.c | 1 -
> .../coresight/coresight-etm4x-core.c | 19 ++++++-------------
> .../coresight/coresight-etm4x-sysfs.c | 7 ++-----
> drivers/hwtracing/coresight/coresight-etm4x.h | 7 ++++++-
> 4 files changed, 14 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-cfg.c b/drivers/hwtracing/coresight/coresight-etm4x-cfg.c
> index c302072b293a..d14d7c8a23e5 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-cfg.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-cfg.c
> @@ -86,7 +86,6 @@ static int etm4_cfg_map_reg_offset(struct etmv4_drvdata *drvdata,
> off_mask = (offset & GENMASK(11, 5));
> do {
> CHECKREGIDX(TRCSSCCRn(0), ss_ctrl, idx, off_mask);
> - CHECKREGIDX(TRCSSCSRn(0), ss_status, idx, off_mask);
> CHECKREGIDX(TRCSSPCICRn(0), ss_pe_cmp, idx, off_mask);
> } while (0);
> } else if ((offset >= TRCCIDCVRn(0)) && (offset <= TRCVMIDCVRn(7))) {
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> index b2b092a76eb5..f55338a4989d 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> @@ -91,7 +91,7 @@ static bool etm4x_sspcicrn_present(struct etmv4_drvdata *drvdata, int n)
> const struct etmv4_caps *caps = &drvdata->caps;
>
> return (n < caps->nr_ss_cmp) && caps->nr_pe_cmp &&
> - (drvdata->config.ss_status[n] & TRCSSCSRn_PC);
> + (caps->ss_cmp[n] & TRCSSCSRn_PC);
> }
>
> u64 etm4x_sysreg_read(u32 offset, bool _relaxed, bool _64bit)
> @@ -573,11 +573,9 @@ static int etm4_enable_hw(struct etmv4_drvdata *drvdata)
> etm4x_relaxed_write32(csa, config->res_ctrl[i], TRCRSCTLRn(i));
>
> for (i = 0; i < caps->nr_ss_cmp; i++) {
> - /* always clear status bit on restart if using single-shot */
> - if (config->ss_ctrl[i] || config->ss_pe_cmp[i])
> - config->ss_status[i] &= ~TRCSSCSRn_STATUS;
> etm4x_relaxed_write32(csa, config->ss_ctrl[i], TRCSSCCRn(i));
> - etm4x_relaxed_write32(csa, config->ss_status[i], TRCSSCSRn(i));
> + /* always clear status and pending bits on restart if using single-shot */
> + etm4x_relaxed_write32(csa, 0x0, TRCSSCSRn(i));
> if (etm4x_sspcicrn_present(drvdata, i))
> etm4x_relaxed_write32(csa, config->ss_pe_cmp[i], TRCSSPCICRn(i));
> }
> @@ -1055,12 +1053,6 @@ static void etm4_disable_hw(struct etmv4_drvdata *drvdata)
>
> etm4_disable_trace_unit(drvdata);
>
> - /* read the status of the single shot comparators */
> - for (i = 0; i < caps->nr_ss_cmp; i++) {
> - config->ss_status[i] =
> - etm4x_relaxed_read32(csa, TRCSSCSRn(i));
> - }
> -
> /* read back the current counter values */
> for (i = 0; i < caps->nr_cntr; i++) {
> config->cntr_val[i] =
> @@ -1503,8 +1495,9 @@ static void etm4_init_arch_data(void *info)
> */
> caps->nr_ss_cmp = FIELD_GET(TRCIDR4_NUMSSCC_MASK, etmidr4);
> for (i = 0; i < caps->nr_ss_cmp; i++) {
> - drvdata->config.ss_status[i] =
> - etm4x_relaxed_read32(csa, TRCSSCSRn(i));
> + caps->ss_cmp[i] = etm4x_relaxed_read32(csa, TRCSSCSRn(i));
> + caps->ss_cmp[i] &= (TRCSSCSRn_PC | TRCSSCSRn_DV |
> + TRCSSCSRn_DA | TRCSSCSRn_INST);

Just re-go through this patch and had a question here:

I’m not sure whether this new change should be documented in the ABI,
given that the TRCSSCSRn_STATUS bit is masked. In my opinion, this
change breaks the existing ABI description.

Description from the ABI document:

What: /sys/bus/coresight/devices/etm<N>/sshot_status
Date: December 2019
KernelVersion: 5.5
Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
Description: (Read) Print the current value of the selected single
shot status register.

Thanks,
Jie

> }
> /* NUMCIDC, bits[27:24] number of Context ID comparators for tracing */
> caps->numcidc = FIELD_GET(TRCIDR4_NUMCIDC_MASK, etmidr4);
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
> index 8bd28e71d4c9..5e26c2ec8f7b 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
> @@ -1829,8 +1829,6 @@ static ssize_t sshot_ctrl_store(struct device *dev,
> raw_spin_lock(&drvdata->spinlock);
> idx = config->ss_idx;
> config->ss_ctrl[idx] = FIELD_PREP(TRCSSCCRn_SAC_ARC_RST_MASK, val);
> - /* must clear bit 31 in related status register on programming */
> - config->ss_status[idx] &= ~TRCSSCSRn_STATUS;
> raw_spin_unlock(&drvdata->spinlock);
> return size;
> }
> @@ -1841,10 +1839,11 @@ static ssize_t sshot_status_show(struct device *dev,
> {
> unsigned long val;
> struct etmv4_drvdata *drvdata = dev_get_drvdata(dev->parent);
> + const struct etmv4_caps *caps = &drvdata->caps;
> struct etmv4_config *config = &drvdata->config;
>
> raw_spin_lock(&drvdata->spinlock);
> - val = config->ss_status[config->ss_idx];
> + val = caps->ss_cmp[config->ss_idx];
> raw_spin_unlock(&drvdata->spinlock);
> return scnprintf(buf, PAGE_SIZE, "%#lx\n", val);
> }
> @@ -1879,8 +1878,6 @@ static ssize_t sshot_pe_ctrl_store(struct device *dev,
> raw_spin_lock(&drvdata->spinlock);
> idx = config->ss_idx;
> config->ss_pe_cmp[idx] = FIELD_PREP(TRCSSPCICRn_PC_MASK, val);
> - /* must clear bit 31 in related status register on programming */
> - config->ss_status[idx] &= ~TRCSSCSRn_STATUS;
> raw_spin_unlock(&drvdata->spinlock);
> return size;
> }
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
> index 8168676f2945..db56c4414873 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.h
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.h
> @@ -213,6 +213,7 @@
> #define TRCACATRn_EXLEVEL_MASK GENMASK(14, 8)
>
> #define TRCSSCSRn_STATUS BIT(31)
> +#define TRCSSCSRn_PENDING BIT(30)
> #define TRCSSCCRn_SAC_ARC_RST_MASK GENMASK(24, 0)
>
> #define TRCSSPCICRn_PC_MASK GENMASK(7, 0)
> @@ -729,6 +730,9 @@ static inline u32 etm4_res_sel_pair(u8 res_sel_idx)
> #define ETM_DEFAULT_ADDR_COMP 0
>
> #define TRCSSCSRn_PC BIT(3)
> +#define TRCSSCSRn_DV BIT(2)
> +#define TRCSSCSRn_DA BIT(1)
> +#define TRCSSCSRn_INST BIT(0)
>
> /* PowerDown Control Register bits */
> #define TRCPDCR_PU BIT(3)
> @@ -861,6 +865,7 @@ enum etm_impdef_type {
> * @lpoverride: If the implementation can support low-power state over.
> * @skip_power_up: Indicates if an implementation can skip powering up
> * the trace unit.
> + * @ss_cmp: Indicates supported single-shot comparators.
> */
> struct etmv4_caps {
> u8 nr_pe;
> @@ -899,6 +904,7 @@ struct etmv4_caps {
> bool atbtrig : 1;
> bool lpoverride : 1;
> bool skip_power_up : 1;
> + u32 ss_cmp[ETM_MAX_SS_CMP];
> };
>
> /**
> @@ -977,7 +983,6 @@ struct etmv4_config {
> u32 res_ctrl[ETM_MAX_RES_SEL]; /* TRCRSCTLRn */
> u8 ss_idx;
> u32 ss_ctrl[ETM_MAX_SS_CMP];
> - u32 ss_status[ETM_MAX_SS_CMP];
> u32 ss_pe_cmp[ETM_MAX_SS_CMP];
> u8 addr_idx;
> u64 addr_val[ETM_MAX_SINGLE_ADDR_CMP];