linux-hardening - [PATCH v5 13/17] firmware: qcom_scm: provide a read-modify-write function

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Date:   Sun, 10 Sep 2023 01:46:14 +0530
From:   Mukesh Ojha <quic_mojha@...cinc.com>
To:     <corbet@....net>, <agross@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <conor+dt@...nel.org>,
        <keescook@...omium.org>, <tony.luck@...el.com>,
        <gpiccoli@...lia.com>, <mathieu.poirier@...aro.org>,
        <catalin.marinas@....com>, <will@...nel.org>,
        <linus.walleij@...aro.org>, <andy.shevchenko@...il.com>,
        <vigneshr@...com>, <nm@...com>, <matthias.bgg@...il.com>,
        <kgene@...nel.org>, <alim.akhtar@...sung.com>,
        <bmasney@...hat.com>, <quic_tsoni@...cinc.com>
CC:     <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-hardening@...r.kernel.org>,
        <linux-remoteproc@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-gpio@...r.kernel.org>, <linux-mediatek@...ts.infradead.org>,
        <linux-samsung-soc@...r.kernel.org>, <kernel@...cinc.com>,
        <quic_mojha@...cinc.com>
Subject: [PATCH v5 13/17] 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            | 20 ++++++++++++++++++++
 include/linux/firmware/qcom/qcom_scm.h |  2 ++
 2 files changed, 22 insertions(+)

diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
index fde33acd46b7..5ea8fc4fd4e8 100644
--- a/drivers/firmware/qcom_scm.c
+++ b/drivers/firmware/qcom_scm.c
@@ -78,6 +78,7 @@ static const char * const qcom_scm_convention_names[] = {
 };
 
 static struct qcom_scm *__scm;
+static DEFINE_SPINLOCK(lock);
 
 static int qcom_scm_clk_enable(void)
 {
@@ -407,6 +408,25 @@ 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;
+
+	spin_lock(&lock);
+	ret = qcom_scm_io_readl(addr, &old);
+	if (ret)
+		goto unlock;
+
+	new = (old & ~mask) | (val & mask);
+
+	ret = qcom_scm_io_writel(addr, new);
+unlock:
+	spin_unlock(&lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(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 250ea4efb7cb..ca41e4eb33ad 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