linux-hardening - [PATCH v3 14/18] firmware: qcom_scm: provide a read-modify-write function

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Message-ID: <1683133352-10046-15-git-send-email-quic_mojha@quicinc.com>
Date:   Wed, 3 May 2023 22:32:28 +0530
From:   Mukesh Ojha <quic_mojha@...cinc.com>
To:     <agross@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>, <corbet@....net>,
        <keescook@...omium.org>, <tony.luck@...el.com>,
        <gpiccoli@...lia.com>, <catalin.marinas@....com>,
        <will@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <robh+dt@...nel.org>, <linus.walleij@...aro.org>,
        <linux-gpio@...r.kernel.org>, <srinivas.kandagatla@...aro.org>
CC:     <linux-arm-msm@...r.kernel.org>,
        <linux-remoteproc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-hardening@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-doc@...r.kernel.org>, "Mukesh Ojha" <quic_mojha@...cinc.com>
Subject: [PATCH v3 14/18] firmware: qcom_scm: provide a read-modify-write function

It was realized by Srinivas K. that there is a need of
read-modify-write scm exported function so that it can
be used by multiple clients.

Let's introduce qcom_scm_io_update_field() which masks
out the bits and write the passed value to that
bit-offset. Subsequent patch will use this function.

Suggested-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
---
 drivers/firmware/qcom_scm.c            | 15 +++++++++++++++
 include/linux/firmware/qcom/qcom_scm.h |  2 ++
 2 files changed, 17 insertions(+)

diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
index fde33acd..003cbcb 100644
--- a/drivers/firmware/qcom_scm.c
+++ b/drivers/firmware/qcom_scm.c
@@ -407,6 +407,21 @@ int qcom_scm_set_remote_state(u32 state, u32 id)
 }
 EXPORT_SYMBOL(qcom_scm_set_remote_state);
 
+int qcom_scm_io_update_field(phys_addr_t addr, unsigned int mask, unsigned int val)
+{
+	unsigned int old, new;
+	int ret;
+
+	ret = qcom_scm_io_readl(addr, &old);
+	if (ret)
+		return ret;
+
+	new = (old & ~mask) | val << (ffs(mask) - 1);
+
+	return qcom_scm_io_writel(addr, new);
+}
+EXPORT_SYMBOL(qcom_scm_io_update_field);
+
 static int __qcom_scm_set_dload_mode(struct device *dev, bool enable)
 {
 	struct qcom_scm_desc desc = {
diff --git a/include/linux/firmware/qcom/qcom_scm.h b/include/linux/firmware/qcom/qcom_scm.h
index 250ea4e..ca41e4e 100644
--- a/include/linux/firmware/qcom/qcom_scm.h
+++ b/include/linux/firmware/qcom/qcom_scm.h
@@ -84,6 +84,8 @@ extern bool qcom_scm_pas_supported(u32 peripheral);
 
 extern int qcom_scm_io_readl(phys_addr_t addr, unsigned int *val);
 extern int qcom_scm_io_writel(phys_addr_t addr, unsigned int val);
+extern int qcom_scm_io_update_field(phys_addr_t addr, unsigned int mask,
+				    unsigned int val);
 
 extern bool qcom_scm_restore_sec_cfg_available(void);
 extern int qcom_scm_restore_sec_cfg(u32 device_id, u32 spare);
-- 
2.7.4