From: timur@codeaurora•org (Timur Tabi)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 3/3] [v2] hvc_dcc: disable user-space access to DCC
Date: Fri, 7 Aug 2015 19:16:35 -0500 [thread overview]
Message-ID: <1438992995-22610-3-git-send-email-timur@codeaurora.org> (raw)
In-Reply-To: <1438992995-22610-1-git-send-email-timur@codeaurora.org>
If the DCC driver loads, then disable user-space access to the DCC so that
we don't have two entities trying to access the DCC at the same time.
Signed-off-by: Timur Tabi <timur@codeaurora•org>
---
arch/arm/include/asm/dcc.h | 15 +++++++++++++++
arch/arm64/include/asm/dcc.h | 11 +++++++++++
drivers/tty/hvc/hvc_dcc.c | 2 ++
3 files changed, 28 insertions(+)
diff --git a/arch/arm/include/asm/dcc.h b/arch/arm/include/asm/dcc.h
index b74899d..c50056b 100644
--- a/arch/arm/include/asm/dcc.h
+++ b/arch/arm/include/asm/dcc.h
@@ -9,8 +9,11 @@
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
+#ifndef __ASM_DCC_H
+#define __ASM_DCC_H
#include <asm/barrier.h>
+#include <asm/hardware/cp14.h>
static inline u32 __dcc_getstatus(void)
{
@@ -39,3 +42,15 @@ static inline void __dcc_putchar(char c)
: "r" (c));
isb();
}
+
+static inline void __dcc_initialize(void)
+{
+ u32 val;
+
+ /* Disable user-space access to DCC */
+ val = MRC14(0, c0, c1, 0);
+ val |= 1 << 12; /* DSCR[Comms] */
+ MCR14(val, 0, c0, c1, 0);
+}
+
+#endif
diff --git a/arch/arm64/include/asm/dcc.h b/arch/arm64/include/asm/dcc.h
index fcb8d7d..a6496f2 100644
--- a/arch/arm64/include/asm/dcc.h
+++ b/arch/arm64/include/asm/dcc.h
@@ -49,4 +49,15 @@ static inline void __dcc_putchar(char c)
isb();
}
+static inline void __dcc_initialize(void)
+{
+ u32 val;
+
+ /* Disable user-space access to DCC */
+ asm volatile ("mrs %0, mdscr_el1\n"
+ " orr %0, %0, #4096\n" /* Set the TDCC bit */
+ " msr mdscr_el1, %0\n"
+ : "=r" (val));
+}
+
#endif
diff --git a/drivers/tty/hvc/hvc_dcc.c b/drivers/tty/hvc/hvc_dcc.c
index 47654ea..e260acb 100644
--- a/drivers/tty/hvc/hvc_dcc.c
+++ b/drivers/tty/hvc/hvc_dcc.c
@@ -76,6 +76,8 @@ static int __init hvc_dcc_console_init(void)
if (!hvc_dcc_check())
return -ENODEV;
+ __dcc_initialize();
+
/* Returns -1 if error */
ret = hvc_instantiate(0, 0, &hvc_dcc_get_put_ops);
--
Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.
next prev parent reply other threads:[~2015-08-08 0:16 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-08 0:16 [PATCH 1/3] [v2] hvc_dcc: don't ignore errors during initialization Timur Tabi
2015-08-08 0:16 ` [PATCH 2/3] [v4] ARM64: TTY: hvc_dcc: Add support for ARM64 dcc Timur Tabi
2015-08-10 9:40 ` Will Deacon
2015-08-17 23:56 ` Timur Tabi
2015-08-18 8:21 ` Dave Martin
2015-08-18 19:07 ` Timur Tabi
2015-08-19 10:14 ` Dave Martin
2015-08-19 16:16 ` Timur Tabi
2015-08-19 16:37 ` Dave Martin
2015-08-24 23:51 ` sboyd at codeaurora.org
2015-09-02 11:10 ` Dave Martin
2015-08-08 0:16 ` Timur Tabi [this message]
2015-08-10 9:47 ` [PATCH 3/3] [v2] hvc_dcc: disable user-space access to DCC Will Deacon
2015-08-17 22:45 ` Timur Tabi
2015-08-10 9:48 ` [PATCH 1/3] [v2] hvc_dcc: don't ignore errors during initialization Will Deacon
2015-08-19 22:51 ` Timur Tabi
-- strict thread matches above, loose matches on Subject: below --
2015-08-19 23:02 [PATCH 1/3] [v3] " Timur Tabi
2015-08-19 23:02 ` [PATCH 3/3] [v2] hvc_dcc: disable user-space access to DCC Timur Tabi
2015-08-20 10:46 ` Will Deacon
2015-08-20 13:02 ` Catalin Marinas
2015-08-20 15:22 ` Timur Tabi
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