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Sun, 21 Jun 2020 20:22:19 -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: <1acc89c9-8a5c-4ba5-9201-2f0124cd7969@www.fastmail.com> In-Reply-To: References: <20200616075121.12837-1-f4bug@amsat.org> <20200616075121.12837-8-f4bug@amsat.org> <914f089d-e81e-4b01-bd70-4702d8b39724@www.fastmail.com> Date: Mon, 22 Jun 2020 09:51:59 +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=64.147.123.17; envelope-from=andrew@aj.id.au; helo=wnew3-smtp.messagingengine.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/21 20:22:22 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, 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 , "Michael S. Tsirkin" , David Hildenbrand , 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 Wed, 17 Jun 2020, at 13:11, Philippe Mathieu-Daud=C3=A9 wrote: > Hi Andrew, >=20 > 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. > >=20 > > What's the basis for this assertion? It's true for the AST2500 and A= ST2600, but=20 > > the AST2400 can run the watchdog from either a 1MHz clock source or = the APB=20 > > clock (which must be at least 16.5MHz on palmetto). The reset state = on the > > AST2400 configures the watchdog for the APB clock rate. > >=20 > > The Linux driver will eventually configure the watchdog for 1MHz mod= e > > regardless so perhaps the AST2400 reset state is a bit of a corner c= ase, but > > I feel the assertion should be watered down a bit? >=20 > What about this description? >=20 > "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." So is this a limitation of QEMUTimer? I was establishing that the hardwa= re can=20 operate at greater than 1 micro-second precision. Andrew