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Mon, 22 Jun 2020 19:46:18 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface User-Agent: Cyrus-JMAP/3.3.0-dev0-543-gda70334-fm-20200618.004-gda703345 Mime-Version: 1.0 Message-Id: In-Reply-To: <3e3459aa-7179-56e5-3e4d-b25f2ea3b450@amsat.org> References: <20200616075121.12837-1-f4bug@amsat.org> <20200616075121.12837-8-f4bug@amsat.org> <914f089d-e81e-4b01-bd70-4702d8b39724@www.fastmail.com> <1acc89c9-8a5c-4ba5-9201-2f0124cd7969@www.fastmail.com> <3e3459aa-7179-56e5-3e4d-b25f2ea3b450@amsat.org> Date: Tue, 23 Jun 2020 09:15:58 +0930 From: "Andrew Jeffery" To: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= , "Cameron Esfahani via" Subject: =?UTF-8?Q?Re:_[PATCH_7/7]_hw/watchdog/wdt=5Faspeed:_Reduce_timer_precisi?= =?UTF-8?Q?on_to_micro-second?= Content-Type: text/plain;charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=66.111.4.229; envelope-from=andrew@aj.id.au; helo=new3-smtp.messagingengine.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/22 19:46:19 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Peter Maydell , qemu-block@nongnu.org, Corey Minyard , David Hildenbrand , "Michael S. Tsirkin" , Mark Cave-Ayland , Max Reitz , qemu-arm@nongnu.org, Joel Stanley , Paolo Bonzini , =?UTF-8?Q?C=C3=A9dric_Le_Goater?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, 22 Jun 2020, at 18:13, Philippe Mathieu-Daud=C3=A9 wrote: > On 6/22/20 2:21 AM, Andrew Jeffery wrote: > > On Wed, 17 Jun 2020, at 13:11, Philippe Mathieu-Daud=C3=A9 wrote: > >> Hi Andrew, > >> > >> On 6/17/20 3:18 AM, Andrew Jeffery wrote: > >>> On Tue, 16 Jun 2020, at 17:21, Philippe Mathieu-Daud=C3=A9 wrote: > >>>> The current implementation uses nano-second precision, while > >>>> the watchdog can not be more precise than a micro-second. > >>> > >>> What's the basis for this assertion? It's true for the AST2500 and= AST2600, but=20 > >>> the AST2400 can run the watchdog from either a 1MHz clock source o= r the APB=20 > >>> clock (which must be at least 16.5MHz on palmetto). The reset stat= e on the > >>> AST2400 configures the watchdog for the APB clock rate. > >>> > >>> The Linux driver will eventually configure the watchdog for 1MHz m= ode > >>> regardless so perhaps the AST2400 reset state is a bit of a corner= case, but > >>> I feel the assertion should be watered down a bit? > >> > >> What about this description? > >> > >> "The current implementation uses nano-second precision, but > >> is not more precise than micro-second precision. > >> Simplify by using a micro-second based timer. > >> Rename the timer 'timer_us' to have the unit explicit." > >=20 > > So is this a limitation of QEMUTimer? I was establishing that the ha= rdware can=20 > > operate at greater than 1 micro-second precision. >=20 > No, I misread your comment about the AST2400 timer which can run > at more than 1Mhz. >=20 > The QEMUTimer doesn't have a such limitation; this patch > aimed to simplify the code for reviewers, but you proved > it incorrect, so let's disregard it. >=20 > Thanks for your careful review! Ah, great, I was wondering where my misunderstanding was. Thanks for clearing that up. Andrew