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[122.58.176.92]) by smtp.gmail.com with ESMTPSA id b26sm25598576pfe.91.2018.11.23.18.03.57 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 23 Nov 2018 18:04:03 -0800 (PST) Subject: Re: [RFC PATCH v2 07/14] m68k: atari: Convert to clocksource API To: Andreas Schwab , Linus Walleij References: Cc: fthain@telegraphics.com.au, Geert Uytterhoeven , Arnd Bergmann , schivers@csc.com.au, Thomas Gleixner , Daniel Lezcano , John Stultz , linux-m68k@lists.linux-m68k.org, "linux-kernel@vger.kernel.org" From: Michael Schmitz Message-ID: <9035c015-85ef-6d14-d12c-f1d5002ee49a@gmail.com> Date: Sat, 24 Nov 2018 15:03:54 +1300 User-Agent: Mozilla/5.0 (X11; Linux ppc; rv:45.0) Gecko/20100101 Icedove/45.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=iso-8859-15; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 20.11.2018 um 23:02 schrieb Andreas Schwab: > On Nov 20 2018, Linus Walleij wrote: > >> Yes you already see the same as I see: this chip MK68901 has >> no less than four timers. I bet the kernel is just using one of them, >> out of habit. > > Note that not all timers can be used freely. Some of them are hardwired > to generate the clock for the serial interfaces. Timer A is used by the DMA sound driver - no workaround possible there. Timer B is used by the framebuffer driver, but it's used only once to reprogram the screen base address at driver init. This one could potentially be used after framebuffer init to improve the clocksource accuracy. Timer D is already used to generate timer interrupts used to poll the ROM port network card / USB adapters. This timer is initialized early in the boot process, which prevents using the MFP UART as serial console (something that I hadn't properly considered before). I'll send a patch for that. I'll also consider using timer B or timer C interrupts instead to poll ROM port hardware. There are no serial drivers anymore that could use the MFP UART hardware, so that point is somewhat moot at present. Cheers, Michael > Andreas. >