[v3] Reinvent BQL-free PIO/MMIO

[PATCH v3 04/10] hpet: move out main counter read into a separate block

Igor Mammedov posted 10 patches 3 months, 1 week ago

Diff against v1 v2 v4
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Maintainers: Richard Henderson <richard.henderson@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, Igor Mammedov <imammedo@redhat.com>, Ani Sinha <anisinha@redhat.com>, Eduardo Habkost <eduardo@habkost.net>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, "Philippe Mathieu-Daudé" <philmd@linaro.org>, Yanan Wang <wangyanan55@huawei.com>, Zhao Liu <zhao1.liu@intel.com>, Peter Xu <peterx@redhat.com>, David Hildenbrand <david@redhat.com>, Peter Maydell <peter.maydell@linaro.org>, Alexander Graf <agraf@csgraf.de>, Mads Ynddal <mads@ynddal.dk>, Michael Rolnik <mrolnik@gmail.com>, Helge Deller <deller@gmx.de>, Cameron Esfahani <dirty@apple.com>, Roman Bolshakov <rbolshakov@ddn.com>, Phil Dennis-Jordan <phil@philjordan.eu>, Marcelo Tosatti <mtosatti@redhat.com>, Reinoud Zandijk <reinoud@netbsd.org>, Sunil Muthuswamy <sunilmut@microsoft.com>, Song Gao <gaosong@loongson.cn>, Laurent Vivier <laurent@vivier.eu>, "Edgar E. Iglesias" <edgar.iglesias@gmail.com>, Aurelien Jarno <aurelien@aurel32.net>, Jiaxun Yang <jiaxun.yang@flygoat.com>, Aleksandar Rikalo <arikalo@gmail.com>, Huacai Chen <chenhuacai@kernel.org>, Stafford Horne <shorne@gmail.com>, Nicholas Piggin <npiggin@gmail.com>, Chinmay Rath <rathc@linux.ibm.com>, Harsh Prateek Bora <harshpb@linux.ibm.com>, Yoshinori Sato <yoshinori.sato@nifty.com>, Ilya Leoshkevich <iii@linux.ibm.com>, Thomas Huth <thuth@redhat.com>, Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>, Artyom Tarasenko <atar4qemu@gmail.com>

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[PATCH v3 04/10] hpet: move out main counter read into a separate block

Posted by Igor Mammedov 3 months, 1 week ago

Follow up patche will switch main counter read to
lock-less mode. As preparation for that move relevant
branch into a separate top level block to make followup
patch cleaner/simplier by reducing contextual noise
when lock-less read is introduced.

no functional changes.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
v3:
  * drop 'addr <= 0xff' as addr == HPET_COUNTER is sufficient
     Peter Xu <peterx@redhat.com>
---
 hw/timer/hpet.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/hw/timer/hpet.c b/hw/timer/hpet.c
index ab5aa59ae4..c776afc0f2 100644
--- a/hw/timer/hpet.c
+++ b/hw/timer/hpet.c
@@ -431,6 +431,16 @@ static uint64_t hpet_ram_read(void *opaque, hwaddr addr,
     addr &= ~4;
 
     QEMU_LOCK_GUARD(&s->lock);
+    if (addr == HPET_COUNTER) {
+        if (hpet_enabled(s)) {
+            cur_tick = hpet_get_ticks(s);
+        } else {
+            cur_tick = s->hpet_counter;
+        }
+        trace_hpet_ram_read_reading_counter(addr & 4, cur_tick);
+        return cur_tick >> shift;
+    }
+
     /*address range of all global regs*/
     if (addr <= 0xff) {
         switch (addr) {
@@ -438,14 +448,6 @@ static uint64_t hpet_ram_read(void *opaque, hwaddr addr,
             return s->capability >> shift;
         case HPET_CFG:
             return s->config >> shift;
-        case HPET_COUNTER:
-            if (hpet_enabled(s)) {
-                cur_tick = hpet_get_ticks(s);
-            } else {
-                cur_tick = s->hpet_counter;
-            }
-            trace_hpet_ram_read_reading_counter(addr & 4, cur_tick);
-            return cur_tick >> shift;
         case HPET_STATUS:
             return s->isr >> shift;
         default:
-- 
2.47.1

Re: [PATCH v3 04/10] hpet: move out main counter read into a separate block

Posted by Peter Xu 3 months ago

On Fri, Aug 08, 2025 at 02:01:31PM +0200, Igor Mammedov wrote:
> Follow up patche will switch main counter read to
> lock-less mode. As preparation for that move relevant
> branch into a separate top level block to make followup
> patch cleaner/simplier by reducing contextual noise
> when lock-less read is introduced.
> 
> no functional changes.
> 
> Signed-off-by: Igor Mammedov <imammedo@redhat.com>

Reviewed-by: Peter Xu <peterx@redhat.com>

-- 
Peter Xu