linux-kernel - [PATCH v2 2/4] firmware: scm: Modify only the DLOAD bit in TCSR register for download mode

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Date:   Wed, 1 Mar 2023 15:25:53 +0530
From:   Mukesh Ojha <quic_mojha@...cinc.com>
To:     <agross@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>
CC:     <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "Mukesh Ojha" <quic_mojha@...cinc.com>
Subject: [PATCH v2 2/4] firmware: scm: Modify only the DLOAD bit in TCSR register for download mode

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.

Originally-by: Poovendhan Selvaraj <quic_poovendh@...cinc.com>
Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
---
Changes in v2:
 - Addressed comment made by Bjorn.
 - Added download mask from patch 3 to this.

 drivers/firmware/qcom_scm.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
index 51eb853..c9f1fad 100644
--- a/drivers/firmware/qcom_scm.c
+++ b/drivers/firmware/qcom_scm.c
@@ -27,6 +27,8 @@ module_param(download_mode, bool, 0);
 #define SCM_HAS_IFACE_CLK	BIT(1)
 #define SCM_HAS_BUS_CLK		BIT(2)
 
+#define QCOM_DOWNLOAD_MODE_MASK 0x30
+
 struct qcom_scm {
 	struct device *dev;
 	struct clk *core_clk;
@@ -419,6 +421,7 @@ static void qcom_scm_set_download_mode(bool enable)
 {
 	bool avail;
 	int ret = 0;
+	u32 val;
 
 	avail = __qcom_scm_is_call_available(__scm->dev,
 					     QCOM_SCM_SVC_BOOT,
@@ -426,8 +429,18 @@ 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);
+		ret = qcom_scm_io_readl(__scm->dload_mode_addr, &val);
+		if (ret) {
+			dev_err(__scm->dev,
+				"failed to read dload mode address value: %d\n", ret);
+			return;
+		}
+
+		val &= ~QCOM_DOWNLOAD_MODE_MASK;
+		if (enable)
+			val |= QCOM_SCM_BOOT_SET_DLOAD_MODE;
+
+		ret = qcom_scm_io_writel(__scm->dload_mode_addr, val);
 	} else {
 		dev_err(__scm->dev,
 			"No available mechanism for setting download mode\n");
-- 
2.7.4