linux-hardening - [PATCH v4 19/21] firmware: scm: Modify only the download bits in TCSR register

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Date:   Wed, 28 Jun 2023 18:04:46 +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>
CC:     <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-hardening@...r.kernel.org>,
        <linux-remoteproc@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-gpio@...r.kernel.org>,
        "Mukesh Ojha" <quic_mojha@...cinc.com>
Subject: [PATCH v4 19/21] firmware: scm: Modify only the download bits in TCSR register

CrashDump collection is based on the DLOAD bit of TCSR register.
To retain other bits, we read the register and modify only the
DLOAD bit as the other bits have their own significance.

Co-developed-by: Poovendhan Selvaraj <quic_poovendh@...cinc.com>
Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
---
 drivers/firmware/qcom_scm.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
index 104d86e49b97..a9ff77d16c42 100644
--- a/drivers/firmware/qcom_scm.c
+++ b/drivers/firmware/qcom_scm.c
@@ -30,6 +30,11 @@ module_param(download_mode, bool, 0);
 #define SCM_HAS_IFACE_CLK	BIT(1)
 #define SCM_HAS_BUS_CLK		BIT(2)
 
+#define QCOM_DOWNLOAD_FULLDUMP		 0x1
+#define QCOM_DOWNLOAD_NODUMP		 0x0
+#define QCOM_DOWNLOAD_MODE_SHIFT	   4
+#define QCOM_DOWNLOAD_MODE_MASK		0x30
+
 struct qcom_scm {
 	struct device *dev;
 	struct clk *core_clk;
@@ -440,6 +445,7 @@ static int __qcom_scm_set_dload_mode(struct device *dev, bool enable)
 static void qcom_scm_set_download_mode(bool enable)
 {
 	bool avail;
+	int val;
 	int ret = 0;
 
 	avail = __qcom_scm_is_call_available(__scm->dev,
@@ -448,8 +454,10 @@ static void qcom_scm_set_download_mode(bool enable)
 	if (avail) {
 		ret = __qcom_scm_set_dload_mode(__scm->dev, enable);
 	} else if (__scm->dload_mode_addr) {
-		ret = qcom_scm_io_writel(__scm->dload_mode_addr,
-				enable ? QCOM_SCM_BOOT_SET_DLOAD_MODE : 0);
+		val = (enable ? QCOM_DOWNLOAD_FULLDUMP : QCOM_DOWNLOAD_NODUMP);
+		val <<= QCOM_DOWNLOAD_MODE_SHIFT;
+		ret = qcom_scm_io_update_field(__scm->dload_mode_addr,
+				QCOM_DOWNLOAD_MODE_MASK, val);
 	} else {
 		dev_err(__scm->dev,
 			"No available mechanism for setting download mode\n");
-- 
2.7.4