[PATCH v1] EDAC/bluefield_edac: Use ARM SMC for EMI access

[PATCH v1] EDAC/bluefield_edac: Use ARM SMC for EMI access

[Shravan Kumar Ramani]

Add secure read/write calls (arm_smccc_smc) to bluefield_edac.
The ACPI table entry decides whether SMC is need for accessing
the registers in the External Memory Interface block. If not,
the registers may be mapped and accessed directly.

v0 -> v1
Updated commit message

Signed-off-by: Shravan Kumar Ramani <shravankr@nvidia.com>
---
 drivers/edac/bluefield_edac.c | 176 ++++++++++++++++++++++++++++++----
 1 file changed, 156 insertions(+), 20 deletions(-)

diff --git a/drivers/edac/bluefield_edac.c b/drivers/edac/bluefield_edac.c
index e4736eb37bfb..cb9e42ef64d1 100644
--- a/drivers/edac/bluefield_edac.c
+++ b/drivers/edac/bluefield_edac.c
@@ -47,13 +47,25 @@
 #define MLXBF_EDAC_MAX_DIMM_PER_MC	2
 #define MLXBF_EDAC_ERROR_GRAIN		8
 
+#define MLXBF_WRITE_REG_32		(0x82000009)
+#define MLXBF_READ_REG_32		(0x8200000A)
+#define MLXBF_WRITE_REG_64		(0x8200000B)
+#define MLXBF_READ_REG_64		(0x8200000C)
+#define MLXBF_SIP_SVC_UID		(0x8200ff01)
+#define MLXBF_SIP_SVC_VERSION		(0x8200ff03)
+
+#define MLXBF_SMCCC_ACCESS_VIOLATION	(-4)
+
+#define MLXBF_SVC_REQ_MAJOR		0
+#define MLXBF_SVC_REQ_MINOR		3
+
 /*
- * Request MLNX_SIP_GET_DIMM_INFO
+ * Request MLXBF_SIP_GET_DIMM_INFO
  *
  * Retrieve information about DIMM on a certain slot.
  *
  * Call register usage:
- * a0: MLNX_SIP_GET_DIMM_INFO
+ * a0: MLXBF_SIP_GET_DIMM_INFO
  * a1: (Memory controller index) << 16 | (Dimm index in memory controller)
  * a2-7: not used.
  *
@@ -61,7 +73,7 @@
  * a0: MLXBF_DIMM_INFO defined below describing the DIMM.
  * a1-3: not used.
  */
-#define MLNX_SIP_GET_DIMM_INFO		0x82000008
+#define MLXBF_SIP_GET_DIMM_INFO		0x82000008
 
 /* Format for the SMC response about the memory information */
 #define MLXBF_DIMM_INFO__SIZE_GB GENMASK_ULL(15, 0)
@@ -72,9 +84,12 @@
 #define MLXBF_DIMM_INFO__PACKAGE_X GENMASK_ULL(31, 24)
 
 struct bluefield_edac_priv {
+	struct device *dev;
 	int dimm_ranks[MLXBF_EDAC_MAX_DIMM_PER_MC];
 	void __iomem *emi_base;
 	int dimm_per_mc;
+	bool svc_sreg_support;
+	u32 sreg_tbl_edac;
 };
 
 static u64 smc_call1(u64 smc_op, u64 smc_arg)
@@ -86,6 +101,71 @@ static u64 smc_call1(u64 smc_op, u64 smc_arg)
 	return res.a0;
 }
 
+static int secure_readl(void __iomem *addr, uint32_t *result, uint32_t sreg_tbl)
+{
+	struct arm_smccc_res res;
+	int status;
+
+	arm_smccc_smc(MLXBF_READ_REG_32, sreg_tbl, (uintptr_t)addr,
+		      0, 0, 0, 0, 0, &res);
+
+	status = res.a0;
+
+	switch (status) {
+	case SMCCC_RET_NOT_SUPPORTED:
+	case MLXBF_SMCCC_ACCESS_VIOLATION:
+		return -1;
+	default:
+		*result = (uint32_t)res.a1;
+		return 0;
+	}
+}
+
+static int secure_writel(void __iomem *addr, uint32_t data, uint32_t sreg_tbl)
+{
+	struct arm_smccc_res res;
+	int status;
+
+	arm_smccc_smc(MLXBF_WRITE_REG_32, sreg_tbl, data, (uintptr_t)addr,
+		      0, 0, 0, 0, &res);
+
+	status = res.a0;
+
+	switch (status) {
+	case SMCCC_RET_NOT_SUPPORTED:
+	case MLXBF_SMCCC_ACCESS_VIOLATION:
+		return -1;
+	default:
+		return 0;
+	}
+}
+
+static int edac_readl(void __iomem *addr, uint32_t *result,
+		      bool sreg_support, uint32_t sreg_tbl)
+{
+	int err = 0;
+
+	if (sreg_support)
+		err = secure_readl(addr, result, sreg_tbl);
+	else
+		*result = readl(addr);
+
+	return err;
+}
+
+static int edac_writel(void __iomem *addr, uint32_t data,
+		       bool sreg_support, uint32_t sreg_tbl)
+{
+	int err = 0;
+
+	if (sreg_support)
+		err = secure_writel(addr, data, sreg_tbl);
+	else
+		writel(data, addr);
+
+	return err;
+}
+
 /*
  * Gather the ECC information from the External Memory Interface registers
  * and report it to the edac handler.
@@ -99,7 +179,7 @@ static void bluefield_gather_report_ecc(struct mem_ctl_info *mci,
 	u32 ecc_latch_select, dram_syndrom, serr, derr, syndrom;
 	enum hw_event_mc_err_type ecc_type;
 	u64 ecc_dimm_addr;
-	int ecc_dimm;
+	int ecc_dimm, err;
 
 	ecc_type = is_single_ecc ? HW_EVENT_ERR_CORRECTED :
 				   HW_EVENT_ERR_UNCORRECTED;
@@ -109,14 +189,22 @@ static void bluefield_gather_report_ecc(struct mem_ctl_info *mci,
 	 * registers with information about the last ECC error occurrence.
 	 */
 	ecc_latch_select = MLXBF_ECC_LATCH_SEL__START;
-	writel(ecc_latch_select, priv->emi_base + MLXBF_ECC_LATCH_SEL);
+	err = edac_writel(priv->emi_base + MLXBF_ECC_LATCH_SEL,
+			  ecc_latch_select, priv->svc_sreg_support,
+			  priv->sreg_tbl_edac);
+	if (err)
+		dev_err(priv->dev, "ECC latch select write failed.\n");
 
 	/*
 	 * Verify that the ECC reported info in the registers is of the
 	 * same type as the one asked to report. If not, just report the
 	 * error without the detailed information.
 	 */
-	dram_syndrom = readl(priv->emi_base + MLXBF_SYNDROM);
+	err = edac_readl(priv->emi_base + MLXBF_SYNDROM, &dram_syndrom,
+			 priv->svc_sreg_support, priv->sreg_tbl_edac);
+	if (err)
+		dev_err(priv->dev, "DRAM syndrom read failed.\n");
+
 	serr = FIELD_GET(MLXBF_SYNDROM__SERR, dram_syndrom);
 	derr = FIELD_GET(MLXBF_SYNDROM__DERR, dram_syndrom);
 	syndrom = FIELD_GET(MLXBF_SYNDROM__SYN, dram_syndrom);
@@ -127,13 +215,24 @@ static void bluefield_gather_report_ecc(struct mem_ctl_info *mci,
 		return;
 	}
 
-	dram_additional_info = readl(priv->emi_base + MLXBF_ADD_INFO);
+	err = edac_readl(priv->emi_base + MLXBF_ADD_INFO, &dram_additional_info,
+			 priv->svc_sreg_support, priv->sreg_tbl_edac);
+	if (err)
+		dev_err(priv->dev, "DRAM additional info read failed.\n");
+
 	err_prank = FIELD_GET(MLXBF_ADD_INFO__ERR_PRANK, dram_additional_info);
 
 	ecc_dimm = (err_prank >= 2 && priv->dimm_ranks[0] <= 2) ? 1 : 0;
 
-	edea0 = readl(priv->emi_base + MLXBF_ERR_ADDR_0);
-	edea1 = readl(priv->emi_base + MLXBF_ERR_ADDR_1);
+	err = edac_readl(priv->emi_base + MLXBF_ERR_ADDR_0, &edea0,
+			 priv->svc_sreg_support, priv->sreg_tbl_edac);
+	if (err)
+		dev_err(priv->dev, "Error addr 0 read failed.\n");
+
+	err = edac_readl(priv->emi_base + MLXBF_ERR_ADDR_1, &edea1,
+			 priv->svc_sreg_support, priv->sreg_tbl_edac);
+	if (err)
+		dev_err(priv->dev, "Error addr 1 read failed.\n");
 
 	ecc_dimm_addr = ((u64)edea1 << 32) | edea0;
 
@@ -147,6 +246,7 @@ static void bluefield_edac_check(struct mem_ctl_info *mci)
 {
 	struct bluefield_edac_priv *priv = mci->pvt_info;
 	u32 ecc_count, single_error_count, double_error_count, ecc_error = 0;
+	int err;
 
 	/*
 	 * The memory controller might not be initialized by the firmware
@@ -155,7 +255,11 @@ static void bluefield_edac_check(struct mem_ctl_info *mci)
 	if (mci->edac_cap == EDAC_FLAG_NONE)
 		return;
 
-	ecc_count = readl(priv->emi_base + MLXBF_ECC_CNT);
+	err = edac_readl(priv->emi_base + MLXBF_ECC_CNT, &ecc_count,
+			 priv->svc_sreg_support, priv->sreg_tbl_edac);
+	if (err)
+		dev_err(priv->dev, "ECC count read failed.\n");
+
 	single_error_count = FIELD_GET(MLXBF_ECC_CNT__SERR_CNT, ecc_count);
 	double_error_count = FIELD_GET(MLXBF_ECC_CNT__DERR_CNT, ecc_count);
 
@@ -172,15 +276,19 @@ static void bluefield_edac_check(struct mem_ctl_info *mci)
 	}
 
 	/* Write to clear reported errors. */
-	if (ecc_count)
-		writel(ecc_error, priv->emi_base + MLXBF_ECC_ERR);
+	if (ecc_count) {
+		err = edac_writel(priv->emi_base + MLXBF_ECC_ERR, ecc_error,
+				  priv->svc_sreg_support, priv->sreg_tbl_edac);
+		if (err)
+			dev_err(priv->dev, "ECC Error write failed.\n");
+	}
 }
 
 /* Initialize the DIMMs information for the given memory controller. */
 static void bluefield_edac_init_dimms(struct mem_ctl_info *mci)
 {
 	struct bluefield_edac_priv *priv = mci->pvt_info;
-	int mem_ctrl_idx = mci->mc_idx;
+	u64 mem_ctrl_idx = mci->mc_idx;
 	struct dimm_info *dimm;
 	u64 smc_info, smc_arg;
 	int is_empty = 1, i;
@@ -189,7 +297,7 @@ static void bluefield_edac_init_dimms(struct mem_ctl_info *mci)
 		dimm = mci->dimms[i];
 
 		smc_arg = mem_ctrl_idx << 16 | i;
-		smc_info = smc_call1(MLNX_SIP_GET_DIMM_INFO, smc_arg);
+		smc_info = smc_call1(MLXBF_SIP_GET_DIMM_INFO, smc_arg);
 
 		if (!FIELD_GET(MLXBF_DIMM_INFO__SIZE_GB, smc_info)) {
 			dimm->mtype = MEM_EMPTY;
@@ -244,6 +352,7 @@ static int bluefield_edac_mc_probe(struct platform_device *pdev)
 	struct bluefield_edac_priv *priv;
 	struct device *dev = &pdev->dev;
 	struct edac_mc_layer layers[1];
+	struct arm_smccc_res res;
 	struct mem_ctl_info *mci;
 	struct resource *emi_res;
 	unsigned int mc_idx, dimm_count;
@@ -280,12 +389,40 @@ static int bluefield_edac_mc_probe(struct platform_device *pdev)
 
 	priv = mci->pvt_info;
 
+	/*
+	 * ACPI indicates whether we use SMCs to access registers or not.
+	 * If sreg_tbl_perf is not present, just assume we're not using SMCs.
+	 */
+	if (device_property_read_u32(dev,
+				     "sec_reg_block", &priv->sreg_tbl_edac)) {
+		priv->svc_sreg_support = false;
+	} else {
+		/*
+		 * Check service version to see if we actually do support the
+		 * needed SMCs. If we have the calls we need, mark support for
+		 * them in the pmc struct.
+		 */
+		arm_smccc_smc(MLXBF_SIP_SVC_VERSION, 0, 0, 0, 0, 0, 0, 0, &res);
+		if (res.a0 == MLXBF_SVC_REQ_MAJOR &&
+		    res.a1 >= MLXBF_SVC_REQ_MINOR) {
+			priv->svc_sreg_support = true;
+		} else {
+			dev_err(dev, "Required SMCs are not supported.\n");
+			ret = -EINVAL;
+			goto err;
+		}
+	}
+
 	priv->dimm_per_mc = dimm_count;
-	priv->emi_base = devm_ioremap_resource(dev, emi_res);
-	if (IS_ERR(priv->emi_base)) {
-		dev_err(dev, "failed to map EMI IO resource\n");
-		ret = PTR_ERR(priv->emi_base);
-		goto err;
+	if (!priv->svc_sreg_support) {
+		priv->emi_base = devm_ioremap_resource(dev, emi_res);
+		if (IS_ERR(priv->emi_base)) {
+			dev_err(dev, "failed to map EMI IO resource\n");
+			ret = PTR_ERR(priv->emi_base);
+			goto err;
+		}
+	} else {
+		priv->emi_base = (void __iomem *)emi_res->start;
 	}
 
 	mci->pdev = dev;
@@ -320,7 +457,6 @@ static int bluefield_edac_mc_probe(struct platform_device *pdev)
 	edac_mc_free(mci);
 
 	return ret;
-
 }
 
 static int bluefield_edac_mc_remove(struct platform_device *pdev)
-- 
2.30.1

Re: [PATCH v1] EDAC/bluefield_edac: Use ARM SMC for EMI access

[Borislav Petkov]

On Wed, Aug 30, 2023 at 06:56:14AM -0400, Shravan Kumar Ramani wrote:
> Add secure read/write calls (arm_smccc_smc) to bluefield_edac.
> The ACPI table entry decides whether SMC is need for accessing

SMC? Self-Modifying Code?

> the registers in the External Memory Interface block. If not,
> the registers may be mapped and accessed directly.

I'm sure there's a human readable explanation for the above.

> v0 -> v1
> Updated commit message

I still have no clue what those secure calls are.

I'm sure there's some ARM documentation which you use in order to
explain why those are needed.

> +static int edac_readl(void __iomem *addr, uint32_t *result,

No "edac_" previxes to driver-local functions. They belong to the EDAC
subsystem.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH v1] EDAC/bluefield_edac: Use ARM SMC for EMI access

[Shravan Ramani]

>> Add secure read/write calls (arm_smccc_smc) to bluefield_edac.
>> The ACPI table entry decides whether SMC is need for accessing
>
> SMC? Self-Modifying Code?

SMC stands for Secure Monitor Call. ARM documentation can be found
here: https://developer.arm.com/documentation/den0028/latest/

SMC is needed by the driver to access certain HW blocks/registers which
can be accessed only from secure state. Whether a certain block requires
these secure calls or not is encoded in the ACPI table entry and passed
on to the driver.

>
>> +static int edac_readl(void __iomem *addr, uint32_t *result,
>
> No "edac_" previxes to driver-local functions. They belong to the EDAC
> subsystem.

Ack, will change the prefixes in v2.

Thanks,
Shravan

Re: [PATCH v1] EDAC/bluefield_edac: Use ARM SMC for EMI access

[Borislav Petkov]

On Thu, Aug 31, 2023 at 04:31:23AM +0000, Shravan Ramani wrote:
> SMC is needed by the driver to access certain HW blocks/registers which
> can be accessed only from secure state. Whether a certain block requires
> these secure calls or not is encoded in the ACPI table entry and passed
> on to the driver.

This sounds like a good start towards explaining why this patch is
needed. Here's an example commit message structure:

1. Prepare the context for the explanation briefly.

2. Explain the problem at hand.

3. "It happens because of <...>"

4. "Fix it by doing X"

5. "(Potentially do Y)."

For more detailed info, see
Documentation/process/submitting-patches.rst, Section "2) Describe your
changes".

Do not talk about what your patch does - that should (hopefully) be
visible from the diff itself. Rather, talk about *why* you're doing what
you're doing.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette