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Tue, 2 Apr 2024 18:00:27 +0300 (MSK) Received: from localhost (100.64.160.123) by p-i-exch-sc-m02.sberdevices.ru (172.16.192.103) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.40; Tue, 2 Apr 2024 18:00:27 +0300 Date: Tue, 2 Apr 2024 18:00:27 +0300 From: Dmitry Rokosov To: Jerome Brunet CC: , , , , , , , , , , , , , Subject: Re: [PATCH v1 2/6] clk: meson: a1: pll: support 'syspll' general-purpose PLL for CPU clock Message-ID: <20240402150027.fptfvov74zwed6vb@CAB-WSD-L081021> References: <20240329205904.25002-1-ddrokosov@salutedevices.com> <20240329205904.25002-3-ddrokosov@salutedevices.com> <1j4jckjftk.fsf@starbuckisacylon.baylibre.com> <20240402121546.qrrc7r5un75464pb@CAB-WSD-L081021> <1jmsqbj0md.fsf@starbuckisacylon.baylibre.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1jmsqbj0md.fsf@starbuckisacylon.baylibre.com> User-Agent: NeoMutt/20220415 X-Originating-IP: [100.64.160.123] X-ClientProxiedBy: p-i-exch-sc-m02.sberdevices.ru (172.16.192.103) To p-i-exch-sc-m02.sberdevices.ru (172.16.192.103) X-KSMG-Rule-ID: 10 X-KSMG-Message-Action: clean X-KSMG-AntiSpam-Lua-Profiles: 184537 [Apr 02 2024] X-KSMG-AntiSpam-Version: 6.1.0.4 X-KSMG-AntiSpam-Envelope-From: ddrokosov@salutedevices.com X-KSMG-AntiSpam-Rate: 0 X-KSMG-AntiSpam-Status: not_detected X-KSMG-AntiSpam-Method: none X-KSMG-AntiSpam-Auth: dkim=none X-KSMG-AntiSpam-Info: LuaCore: 14 0.3.14 5a0c43d8a1c3c0e5b0916cc02a90d4b950c01f96, {Track_E25351}, {Tracking_from_domain_doesnt_match_to}, smtp.sberdevices.ru:5.0.1,7.1.1;d41d8cd98f00b204e9800998ecf8427e.com:7.1.1;salutedevices.com:7.1.1;127.0.0.199:7.1.2;100.64.160.123:7.1.2, FromAlignment: s, ApMailHostAddress: 100.64.160.123 X-MS-Exchange-Organization-SCL: -1 X-KSMG-AntiSpam-Interceptor-Info: scan successful X-KSMG-AntiPhishing: Clean X-KSMG-LinksScanning: Clean X-KSMG-AntiVirus: Kaspersky Secure Mail Gateway, version 2.0.1.6960, bases: 2024/04/02 07:07:00 #24571916 X-KSMG-AntiVirus-Status: Clean, skipped X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240402_080035_612822_77135ADF X-CRM114-Status: GOOD ( 37.39 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Apr 02, 2024 at 04:27:17PM +0200, Jerome Brunet wrote: > > On Tue 02 Apr 2024 at 15:15, Dmitry Rokosov wrote: > > > On Tue, Apr 02, 2024 at 11:00:42AM +0200, Jerome Brunet wrote: > >> > >> On Fri 29 Mar 2024 at 23:58, Dmitry Rokosov wrote: > >> > >> > The 'syspll' PLL, also known as the system PLL, is a general and > >> > essential PLL responsible for generating the CPU clock frequency. > >> > With its wide-ranging capabilities, it is designed to accommodate > >> > frequencies within the range of 768MHz to 1536MHz. > >> > > >> > Signed-off-by: Dmitry Rokosov > >> > --- > >> > drivers/clk/meson/a1-pll.c | 78 ++++++++++++++++++++++++++++++++++++++ > >> > drivers/clk/meson/a1-pll.h | 6 +++ > >> > 2 files changed, 84 insertions(+) > >> > > >> > diff --git a/drivers/clk/meson/a1-pll.c b/drivers/clk/meson/a1-pll.c > >> > index 60b2e53e7e51..02fd2d325cc6 100644 > >> > --- a/drivers/clk/meson/a1-pll.c > >> > +++ b/drivers/clk/meson/a1-pll.c > >> > @@ -138,6 +138,81 @@ static struct clk_regmap hifi_pll = { > >> > }, > >> > }; > >> > > >> > +static const struct pll_mult_range sys_pll_mult_range = { > >> > + .min = 32, > >> > + .max = 64, > >> > +}; > >> > + > >> > +/* > >> > + * We assume that the sys_pll_clk has already been set up by the low-level > >> > + * bootloaders as the main CPU PLL source. Therefore, it is not necessary to > >> > + * run the initialization sequence. > >> > + */ > >> > >> I see no reason to make such assumption. > >> This clock is no read-only, it apparently is able to re-lock so assuming > >> anything from the bootloader is just asking from trouble > >> > > > > Indeed, I have implemented the following initialization sequence. I have > > dumped the bootloader setup and included it in the definition of my > > sys_pll. However, I have encountered an issue with the enable bit. If I > > leave the enable bit switched on by default, there is a possibility that > > the bootloader selects a fixed CPU clock while the sys_pll should be > > switched off. On the other hand, if I keep the enable bit switched off > > by default, the bootloader might configure the CPU clock to use sys_pll, > > resulting in the execution halting when the initialization sequence is > > run. This situation has led me to assume that we should place our trust > > in the bootloader setup. > > > > If you believe it is necessary to include the initialization sequence, I > > can prepare it with the sys_pll enabled by default. > > I just noted your initial comment is misleading. > > You could submit a patch to apply the init sequence only if the PLL is > not already enabled. Maybe even condition that to flag in the pll data > to avoid applying it to the other platforms for now. > Ah, I see. Okay, no problem, I will prepare such patch to common meson clk-pll. [...] -- Thank you, Dmitry _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel