Re: [PATCH v8 4/4] coresight: cti: expose banked sysfs registers for Qualcomm extended CTI

From: Yingchao Deng (Consultant)

Date: Mon Apr 27 2026 - 22:18:33 EST


On 4/28/2026 2:15 AM, Leo Yan wrote:
On Sun, Apr 26, 2026 at 05:44:41PM +0800, Yingchao Deng wrote:
Qualcomm extended CTI implements banked trigger status and integration
registers, where each bank covers 32 triggers. Multiple instances of
these registers are required to expose the full trigger space.

Add static sysfs entries for the banked CTI registers and control their
visibility based on the underlying hardware configuration. Numbered
sysfs nodes are hidden on standard ARM CTIs, preserving the existing ABI.
On Qualcomm CTIs, only banked registers backed by hardware are exposed,
with the number of visible banks derived from nr_trig_max.

This ensures that userspace only sees registers that are actually
implemented, while maintaining compatibility with existing CTI tooling.

Signed-off-by: Yingchao Deng <yingchao.deng@xxxxxxxxxxxxxxxx>
---
drivers/hwtracing/coresight/coresight-cti-sysfs.c | 58 +++++++++++++++++++++++
1 file changed, 58 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-cti-sysfs.c b/drivers/hwtracing/coresight/coresight-cti-sysfs.c
index 8b70e7e38ea3..046757e4e9b6 100644
--- a/drivers/hwtracing/coresight/coresight-cti-sysfs.c
+++ b/drivers/hwtracing/coresight/coresight-cti-sysfs.c
@@ -512,18 +512,36 @@ static struct attribute *coresight_cti_regs_attrs[] = {
&dev_attr_appclear.attr,
&dev_attr_apppulse.attr,
coresight_cti_reg(triginstatus, CTITRIGINSTATUS),
+ coresight_cti_reg(triginstatus1, CTI_REG_SET_NR_CONST(CTITRIGINSTATUS, 1)),
How about extend the cs_off_attribute struct:

struct cs_off_attribute {
struct device_attribute attr;
u32 off;
u32 index;
};

// by default, the index is 0
#define coresight_cti_reg(name, offset) \
(&((struct cs_off_attribute[]) { \
{ \
__ATTR(name, 0444, coresight_cti_reg_show, NULL), \
offset \
0 \
} \
})[0].attr.attr)

// For the register with index
#define coresight_cti_reg_index(name, offset, index) \
(&((struct cs_off_attribute[]) { \
{ \
__ATTR(name, 0444, coresight_cti_reg_show, NULL), \
offset \
index \
} \
})[0].attr.attr)

coresight_cti_reg_index(triginstatus1, CTITRIGINSTATUS, 1),

+ coresight_cti_reg(triginstatus2, CTI_REG_SET_NR_CONST(CTITRIGINSTATUS, 2)),
+ coresight_cti_reg(triginstatus3, CTI_REG_SET_NR_CONST(CTITRIGINSTATUS, 3)),
coresight_cti_reg(trigoutstatus, CTITRIGOUTSTATUS),
+ coresight_cti_reg(trigoutstatus1, CTI_REG_SET_NR_CONST(CTITRIGOUTSTATUS, 1)),
+ coresight_cti_reg(trigoutstatus2, CTI_REG_SET_NR_CONST(CTITRIGOUTSTATUS, 2)),
+ coresight_cti_reg(trigoutstatus3, CTI_REG_SET_NR_CONST(CTITRIGOUTSTATUS, 3)),
coresight_cti_reg(chinstatus, CTICHINSTATUS),
coresight_cti_reg(choutstatus, CTICHOUTSTATUS),
#ifdef CONFIG_CORESIGHT_CTI_INTEGRATION_REGS
coresight_cti_reg_rw(itctrl, CORESIGHT_ITCTRL),
coresight_cti_reg(ittrigin, ITTRIGIN),
+ coresight_cti_reg(ittrigin1, CTI_REG_SET_NR_CONST(ITTRIGIN, 1)),
+ coresight_cti_reg(ittrigin2, CTI_REG_SET_NR_CONST(ITTRIGIN, 2)),
+ coresight_cti_reg(ittrigin3, CTI_REG_SET_NR_CONST(ITTRIGIN, 3)),
coresight_cti_reg(itchin, ITCHIN),
coresight_cti_reg_rw(ittrigout, ITTRIGOUT),
+ coresight_cti_reg_rw(ittrigout1, CTI_REG_SET_NR_CONST(ITTRIGOUT, 1)),
+ coresight_cti_reg_rw(ittrigout2, CTI_REG_SET_NR_CONST(ITTRIGOUT, 2)),
+ coresight_cti_reg_rw(ittrigout3, CTI_REG_SET_NR_CONST(ITTRIGOUT, 3)),
coresight_cti_reg_rw(itchout, ITCHOUT),
coresight_cti_reg(itchoutack, ITCHOUTACK),
coresight_cti_reg(ittrigoutack, ITTRIGOUTACK),
+ coresight_cti_reg(ittrigoutack1, CTI_REG_SET_NR_CONST(ITTRIGOUTACK, 1)),
+ coresight_cti_reg(ittrigoutack2, CTI_REG_SET_NR_CONST(ITTRIGOUTACK, 2)),
+ coresight_cti_reg(ittrigoutack3, CTI_REG_SET_NR_CONST(ITTRIGOUTACK, 3)),
coresight_cti_reg_wo(ittriginack, ITTRIGINACK),
+ coresight_cti_reg_wo(ittriginack1, CTI_REG_SET_NR_CONST(ITTRIGINACK, 1)),
+ coresight_cti_reg_wo(ittriginack2, CTI_REG_SET_NR_CONST(ITTRIGINACK, 2)),
+ coresight_cti_reg_wo(ittriginack3, CTI_REG_SET_NR_CONST(ITTRIGINACK, 3)),
coresight_cti_reg_wo(itchinack, ITCHINACK),
#endif
NULL,
@@ -534,10 +552,50 @@ static umode_t coresight_cti_regs_is_visible(struct kobject *kobj,
{
struct device *dev = kobj_to_dev(kobj);
struct cti_drvdata *drvdata = dev_get_drvdata(dev->parent);
+ static const char * const qcom_suffix_registers[] = {
+ "triginstatus",
+ "trigoutstatus",
+#ifdef CONFIG_CORESIGHT_CTI_INTEGRATION_REGS
+ "ittrigin",
+ "ittrigout",
+ "ittriginack",
+ "ittrigoutack",
+#endif
+ };
+ int i, nr, max_bank;
+ size_t len;
if (attr == &dev_attr_asicctl.attr && !drvdata->config.asicctl_impl)
return 0;
+ /*
+ * Banked regs are exposed as <qcom_suffix_registers><nr> (nr = 1..3).
+ * - Hide them on standard CTIs.
+ * - On QCOM CTIs, hide suffixes beyond the number of banks implied
+ * by nr_trig_max (32 triggers per bank).
+ */
+ for (i = 0; i < ARRAY_SIZE(qcom_suffix_registers); i++) {
This can be general for a register with index? Like:

for (i = 0; i < ARRAY_SIZE(registers_with_index); i++) {

+ len = strlen(qcom_suffix_registers[i]);
+
+ if (strncmp(attr->name, qcom_suffix_registers[i], len))
+ continue;
+
+ if (kstrtoint(attr->name + len, 10, &nr))
+ continue;
+
+ if (!drvdata->is_qcom_cti)
+ return 0;
+
+ if (nr < 1 || nr > 3)
+ return 0;
+
+ max_bank = DIV_ROUND_UP(drvdata->config.nr_trig_max, 32) - 1;
+ if (nr > max_bank)
+ return 0;
Directly check the attr's index here?

struct cs_off_attribute *cti_attr =
container_of(attr, struct cs_off_attribute, attr);

max_bank = DIV_ROUND_UP(drvdata->config.nr_trig_max, 32);
if (cti_attr->index >= max_bank)
return 0;

Thanks,
Leo
Will update.

Thanks,
Yingchao