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Re: [PATCH 3/3] hw/dma/xilinx_axidma.c: Switch to transaction-based ptim


From: Philippe Mathieu-Daudé
Subject: Re: [PATCH 3/3] hw/dma/xilinx_axidma.c: Switch to transaction-based ptimer API
Date: Thu, 17 Oct 2019 17:25:47 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1

On 10/17/19 5:06 PM, Peter Maydell wrote:
On Thu, 17 Oct 2019 at 16:01, Philippe Mathieu-Daudé <address@hidden> wrote:

Hi Peter,

On 10/17/19 3:21 PM, Peter Maydell wrote:
Switch the xilinx_axidma code away from bottom-half based ptimers to
the new transaction-based ptimer API.  This just requires adding
begin/commit calls around the various places that modify the ptimer
state, and using the new ptimer_init() function to create the timer.

Signed-off-by: Peter Maydell <address@hidden>
---
   hw/dma/xilinx_axidma.c | 9 +++++----
   1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/hw/dma/xilinx_axidma.c b/hw/dma/xilinx_axidma.c
index e035d1f7504..fb3a978e282 100644
--- a/hw/dma/xilinx_axidma.c
+++ b/hw/dma/xilinx_axidma.c
@@ -31,7 +31,6 @@
   #include "hw/ptimer.h"
   #include "hw/qdev-properties.h"
   #include "qemu/log.h"
-#include "qemu/main-loop.h"
   #include "qemu/module.h"

   #include "hw/stream.h"
@@ -104,7 +103,6 @@ enum {
   };

   struct Stream {
-    QEMUBH *bh;
       ptimer_state *ptimer;
       qemu_irq irq;

@@ -242,6 +240,7 @@ static void stream_complete(struct Stream *s)
       unsigned int comp_delay;

       /* Start the delayed timer.  */
+    ptimer_transaction_begin(s->ptimer);
       comp_delay = s->regs[R_DMACR] >> 24;
       if (comp_delay) {
           ptimer_stop(s->ptimer);
@@ -255,6 +254,7 @@ static void stream_complete(struct Stream *s)
           s->regs[R_DMASR] |= DMASR_IOC_IRQ;
           stream_reload_complete_cnt(s);
       }
+    ptimer_transaction_commit(s->ptimer);

I'd restrict the transaction here within the if() statement:

-- >8 --
@@ -244,9 +244,11 @@ static void stream_complete(struct Stream *s)
       /* Start the delayed timer.  */
       comp_delay = s->regs[R_DMACR] >> 24;
       if (comp_delay) {
+        ptimer_transaction_begin(s->ptimer);
           ptimer_stop(s->ptimer);
           ptimer_set_count(s->ptimer, comp_delay);
           ptimer_run(s->ptimer, 1);
+        ptimer_transaction_commit(s->ptimer);
       }

       s->complete_cnt--;

The timer_hit callback function itself writes to
s->complete_cnt, so we don't want to allow it to
be called (via the commit()) before stream_complete()
is done with changing that state.

Indeed we have timer_hit() -> stream_reload_complete_cnt() which uses s->complete_cnt.

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>



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