linux-kernel - [PATCH v2 1/3] soc: samsung: exynos-pmu: allow specifying read & write access tables for secure regmap

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Message-Id: <20251009-gs101-pmu-regmap-tables-v2-1-2d64f5261952@linaro.org>
Date: Thu, 09 Oct 2025 10:31:25 +0100
From: André Draszik <andre.draszik@...aro.org>
To: Krzysztof Kozlowski <krzk@...nel.org>, 
 Alim Akhtar <alim.akhtar@...sung.com>, 
 Peter Griffin <peter.griffin@...aro.org>, 
 Tudor Ambarus <tudor.ambarus@...aro.org>
Cc: Will McVicker <willmcvicker@...gle.com>, kernel-team@...roid.com, 
 linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org, 
 linux-kernel@...r.kernel.org, 
 André Draszik <andre.draszik@...aro.org>, 
 Sam Protsenko <semen.protsenko@...aro.org>
Subject: [PATCH v2 1/3] soc: samsung: exynos-pmu: allow specifying read &
 write access tables for secure regmap

Accessing non-existent PMU registers causes an SError, halting the
system.

regmap can help us with that by allowing to pass the list of valid
registers as part of the config during creation. When this driver
creates a new regmap itself rather than relying on
syscon_node_to_regmap(), it's therefore easily possible to hook in
custom access tables for valid read and write registers.

Specifying access tables avoids SErrors for invalid registers and
instead the regmap core can just return an error. Outside drivers, this
is also helpful when using debugfs to access the regmap.

Make it possible for drivers to specify read and write tables to be
used on creation of the secure regmap by adding respective fields to
struct exynos_pmu_data. Also add kerneldoc to same struct while
updating it.

Reviewed-by: Sam Protsenko <semen.protsenko@...aro.org>
Signed-off-by: André Draszik <andre.draszik@...aro.org>
---
v2:
* add regmap_access_table forward declaration (Sam)
* add kerneldoc for struct exynos_pmu_data (Sam)

The regmap_access_table forward declaration declaration triggers a
checkpatch warning: 'struct regmap_access_table should normally be
const'. In this case, it's just a forware declaration and the warning
can be ignored.
---
 drivers/soc/samsung/exynos-pmu.c |  3 +++
 drivers/soc/samsung/exynos-pmu.h | 30 ++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/drivers/soc/samsung/exynos-pmu.c b/drivers/soc/samsung/exynos-pmu.c
index 22c50ca2aa79bf1945255ee6cc7443d7309b2573..9f416de03610b1727d8cc77616e5c87e2525cc69 100644
--- a/drivers/soc/samsung/exynos-pmu.c
+++ b/drivers/soc/samsung/exynos-pmu.c
@@ -635,6 +635,9 @@ static int exynos_pmu_probe(struct platform_device *pdev)
 		pmu_regmcfg = regmap_smccfg;
 		pmu_regmcfg.max_register = resource_size(res) -
 					   pmu_regmcfg.reg_stride;
+		pmu_regmcfg.wr_table = pmu_context->pmu_data->wr_table;
+		pmu_regmcfg.rd_table = pmu_context->pmu_data->rd_table;
+
 		/* Need physical address for SMC call */
 		regmap = devm_regmap_init(dev, NULL,
 					  (void *)(uintptr_t)res->start,
diff --git a/drivers/soc/samsung/exynos-pmu.h b/drivers/soc/samsung/exynos-pmu.h
index 0938bb4fe15f439e2d8bddeec51b6077e79a7e84..1658a55fe61c6fe70cc4cb0fcdcea2756096a268 100644
--- a/drivers/soc/samsung/exynos-pmu.h
+++ b/drivers/soc/samsung/exynos-pmu.h
@@ -13,11 +13,38 @@
 
 #define PMU_TABLE_END	(-1U)
 
+struct regmap_access_table;
+
 struct exynos_pmu_conf {
 	unsigned int offset;
 	u8 val[NUM_SYS_POWERDOWN];
 };
 
+/**
+ * struct exynos_pmu_data - of_device_id (match) data
+ *
+ * @pmu_config: Optional table detailing register writes for target system
+ *              states: SYS_AFTR, SYS_LPA, SYS_SLEEP.
+ * @pmu_config_extra: Optional secondary table detailing additional register
+ *                    writes for target system states: SYS_AFTR, SYS_LPA,
+ *                    SYS_SLEEP.
+ * @pmu_secure: Whether or not PMU register writes need to be done via SMC call.
+ * @pmu_cpuhp: Whether or not extra handling is required for CPU hotplug and
+ *             CPUidle outside of standard PSCI calls, due to non-compliant
+ *             firmware.
+ * @pmu_init: Optional init function.
+ * @powerdown_conf: Optional callback before entering target system states:
+ *                  SYS_AFTR, SYS_LPA, SYS_SLEEP. This will be invoked before
+ *                  the registers from @pmu_config are written.
+ * @powerdown_conf_extra: Optional secondary callback before entering
+ *                        target system states: SYS_AFTR, SYS_LPA, SYS_SLEEP.
+ *                        This will be invoked after @pmu_config registers have
+ *                        been written.
+ * @rd_table: A table of readable register ranges in case a custom regmap is
+ *            used (i.e. when @pmu_secure is @true).
+ * @wr_table: A table of writable register ranges in case a custom regmap is
+ *            used (i.e. when @pmu_secure is @true).
+ */
 struct exynos_pmu_data {
 	const struct exynos_pmu_conf *pmu_config;
 	const struct exynos_pmu_conf *pmu_config_extra;
@@ -27,6 +54,9 @@ struct exynos_pmu_data {
 	void (*pmu_init)(void);
 	void (*powerdown_conf)(enum sys_powerdown);
 	void (*powerdown_conf_extra)(enum sys_powerdown);
+
+	const struct regmap_access_table *rd_table;
+	const struct regmap_access_table *wr_table;
 };
 
 extern void __iomem *pmu_base_addr;

-- 
2.51.0.710.ga91ca5db03-goog