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Groups > linux.kernel > #1174766 > unrolled thread
| Started by | Timur Tabi <timur@codeaurora.org> |
|---|---|
| First post | 2015-06-30 23:30 +0200 |
| Last post | 2015-07-03 17:00 +0200 |
| Articles | 3 — 2 participants |
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[PATCH 4/4] hvc_dcc: disable user-space access to DCC Timur Tabi <timur@codeaurora.org> - 2015-06-30 23:30 +0200
Re: [PATCH 4/4] hvc_dcc: disable user-space access to DCC Stephen Boyd <sboyd@codeaurora.org> - 2015-07-02 02:10 +0200
Re: [PATCH 4/4] hvc_dcc: disable user-space access to DCC Timur Tabi <timur@codeaurora.org> - 2015-07-03 17:00 +0200
| From | Timur Tabi <timur@codeaurora.org> |
|---|---|
| Date | 2015-06-30 23:30 +0200 |
| Subject | [PATCH 4/4] hvc_dcc: disable user-space access to DCC |
| Message-ID | <pHbgm-5xn-5@gated-at.bofh.it> |
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..7843e62 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 ("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 f8b8cf2..5ccafa4 100644
--- a/drivers/tty/hvc/hvc_dcc.c
+++ b/drivers/tty/hvc/hvc_dcc.c
@@ -231,6 +231,8 @@ 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.
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| From | Stephen Boyd <sboyd@codeaurora.org> |
|---|---|
| Date | 2015-07-02 02:10 +0200 |
| Message-ID | <pHAeJ-3Ll-1@gated-at.bofh.it> |
| In reply to | #1174766 |
On 06/30/2015 02:23 PM, Timur Tabi wrote:
> 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>
That's new.
>
> 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);
> +}
Nitpick: We do raw cp14 accesses for other functions in this file, so it
would be nice to be consistent throughout.
> +
> +#endif
> diff --git a/arch/arm64/include/asm/dcc.h b/arch/arm64/include/asm/dcc.h
> index fcb8d7d..7843e62 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 ("mrs %0, mdscr_el1\n"
shouldn't this be volatile?
> + " orr %0, %0, #4096\n" /* Set the TDCC bit */
arm64 has some #defines in debug-monitors.h which we should probably
extend to have this bit as a #define too.
> + " msr mdscr_el1, %0\n"
> + : "=r" (val));
> +}
> +
> #endif
>
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
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| From | Timur Tabi <timur@codeaurora.org> |
|---|---|
| Date | 2015-07-03 17:00 +0200 |
| Message-ID | <pIaBA-1kt-13@gated-at.bofh.it> |
| In reply to | #1175620 |
On Jul 1, 2015, at 8:00 PM, Stephen Boyd wrote:
>>
>> #include <asm/barrier.h>
>> +#include <asm/hardware/cp14.h>
>
> That's new.
And no one else is using it either.
>>
>> +
>> +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);
>> +}
>
> Nitpick: We do raw cp14 accesses for other functions in this file, so it
> would be nice to be consistent throughout.
I agree, but I didn't want to expand the scope of this patch beyond what it's supposed to do.
>>
>> +static inline void __dcc_initialize(void)
>> +{
>> + u32 val;
>> +
>> + /* Disable user-space access to DCC */
>> + asm ("mrs %0, mdscr_el1\n"
>
> shouldn't this be volatile?
Well, I figured it wasn't important exactly why these instructions are executed, since it just disables user-space. I usually get chewed out by someone if I add volatile where it's not needed, so I didn't add it this time.
>
>> + " orr %0, %0, #4096\n" /* Set the TDCC bit */
>
> arm64 has some #defines in debug-monitors.h which we should probably
> extend to have this bit as a #define too.
Hmmm, the only thing I see in debug_monitors.h that seems applicable are the mdscr_write() and mdscr_read() functions, which seem to overlap cp14.h.
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