[cadcdev-svn-commits] [SCM] branch master updated. v2.0.0-1412-g34f7e943

[falcovorbis <fal...@us...>]

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- Log -----------------------------------------------------------------
commit 34f7e943d311cd0105eb012571e7fcda41d3370d
Author: Paul Cercueil <pa...@cr...>
Date:   Thu May 30 21:06:02 2024 +0200

    Work around MMU issue with SQs (#598)
    
    * mmu: Add functions mmu_disable() and mmu_restore()
    
    These functions can be used to temporarily disable MMU address
    translation.
    
    Signed-off-by: Paul Cercueil <pa...@cr...>
    
    * sq: Work around MMU issue by... disabling MMU
    
    This change makes it possible to use SQs in a program that uses the MMU,
    by disabling the MMU in sq_lock(), and re-enable it again in
    mmu_restore().
    
    This means that memory-mapped data must not be accessed while the SQ is
    locked. This should be fine, as it wasn't working properly before, so
    it's not a regression.
    
    Signed-off-by: Paul Cercueil <pa...@cr...>
    
    ---------
    
    Signed-off-by: Paul Cercueil <pa...@cr...>

-----------------------------------------------------------------------

Summary of changes:
 kernel/arch/dreamcast/hardware/sq.c      |  9 +++++++++
 kernel/arch/dreamcast/include/arch/mmu.h | 17 +++++++++++++++++
 kernel/arch/dreamcast/kernel/mmu.c       | 12 ++++++++++++
 3 files changed, 38 insertions(+)

diff --git a/kernel/arch/dreamcast/hardware/sq.c b/kernel/arch/dreamcast/hardware/sq.c
index 7f34633a..10ef13bd 100644
--- a/kernel/arch/dreamcast/hardware/sq.c
+++ b/kernel/arch/dreamcast/hardware/sq.c
@@ -8,6 +8,7 @@
 */
 
 #include <arch/cache.h>
+#include <arch/mmu.h>
 #include <dc/sq.h>
 #include <kos/dbglog.h>
 #include <kos/mutex.h>
@@ -40,12 +41,20 @@
 
 static mutex_t sq_mutex = MUTEX_INITIALIZER;
 
+static mmu_token_t mmu_token;
+
 void sq_lock(void *dest) {
     mutex_lock(&sq_mutex);
+
+    /* Disable MMU, because SQs work differently when it's enabled, and we
+     * don't support it. */
+    mmu_token = mmu_disable();
+
     SET_QACR_REGS(dest, dest);
 }
 
 void sq_unlock(void) {
+    mmu_restore(mmu_token);
     mutex_unlock(&sq_mutex);
 }
 
diff --git a/kernel/arch/dreamcast/include/arch/mmu.h b/kernel/arch/dreamcast/include/arch/mmu.h
index ad0c3aca..5b4a6cf8 100644
--- a/kernel/arch/dreamcast/include/arch/mmu.h
+++ b/kernel/arch/dreamcast/include/arch/mmu.h
@@ -195,6 +195,9 @@ typedef struct mmucontext {
     to do so.
 */
 extern mmucontext_t *mmu_cxt_current;
+
+struct mmu_token;
+typedef struct mmu_token *mmu_token_t;
 /** \endcond */
 
 /** \brief   Set the "current" page tables for TLB handling.
@@ -370,6 +373,20 @@ void mmu_shutdown(void);
  */
 void mmu_reset_itlb(void);
 
+/** \brief   Temporarily disable MMU address translation.
+    \ingroup mmu
+
+    \return                 An opaque token to be passed to mmu_restore()
+ */
+mmu_token_t mmu_disable(void);
+
+/** \brief   Restore MMU address translation.
+    \ingroup mmu
+
+    \param  token           The opaque token obtained from mmu_disable()
+ */
+void mmu_restore(mmu_token_t token);
+
 __END_DECLS
 
 #endif  /* __ARCH_MMU_H */
diff --git a/kernel/arch/dreamcast/kernel/mmu.c b/kernel/arch/dreamcast/kernel/mmu.c
index 8d81fdef..466a1561 100644
--- a/kernel/arch/dreamcast/kernel/mmu.c
+++ b/kernel/arch/dreamcast/kernel/mmu.c
@@ -766,3 +766,15 @@ void mmu_shutdown(void) {
     irq_set_handler(EXC_DTLB_PV_WRITE, NULL, NULL);
     irq_set_handler(EXC_INITIAL_PAGE_WRITE, NULL, NULL);
 }
+
+mmu_token_t mmu_disable(void) {
+    mmu_token_t token = (mmu_token_t)*mmucr;
+
+    *mmucr &= ~0x1;
+
+    return token;
+}
+
+void mmu_restore(mmu_token_t token) {
+    *mmucr = (uint32)token;
+}


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