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[91.78.208.152]) by smtp.googlemail.com with ESMTPSA id w5sm3843660ljj.47.2020.04.09.12.16.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 09 Apr 2020 12:16:47 -0700 (PDT) Subject: Re: [PATCH v6 09/14] memory: tegra: Add EMC scaling support code for Tegra210 To: Thierry Reding , Rob Herring Cc: Jon Hunter , Michael Turquette , Stephen Boyd , Joseph Lo , linux-tegra@vger.kernel.org, devicetree@vger.kernel.org, linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20200409175238.3586487-1-thierry.reding@gmail.com> <20200409175238.3586487-10-thierry.reding@gmail.com> From: Dmitry Osipenko Message-ID: Date: Thu, 9 Apr 2020 22:16:46 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200409175238.3586487-10-thierry.reding@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org 09.04.2020 20:52, Thierry Reding пишет: ... > +static int tegra210_emc_set_rate(struct device *dev, > + const struct tegra210_clk_emc_config *config) > +{ > + struct tegra210_emc *emc = dev_get_drvdata(dev); > + struct tegra210_emc_timing *timing = NULL; > + unsigned long rate = config->rate; > + s64 last_change_delay; > + unsigned long flags; > + unsigned int i; > + > + if (rate == emc->last->rate * 1000UL) > + return 0; Couldn't all the rates be expressed in Hz? Then you won't need all these multiplications by 1000. > + for (i = 0; i < emc->num_timings; i++) { > + if (emc->timings[i].rate * 1000UL == rate) { > + timing = &emc->timings[i]; > + break; > + } > + } > + > + if (!timing) > + return -EINVAL; > + > + if (rate > 204000000 && !timing->trained) > + return -EINVAL; > + > + emc->next = timing; > + last_change_delay = ktime_us_delta(ktime_get(), emc->clkchange_time); > + > + /* XXX use non-busy-looping sleep? */ > + if ((last_change_delay >= 0) && > + (last_change_delay < emc->clkchange_delay)) > + udelay(emc->clkchange_delay - (int)last_change_delay); > + > + spin_lock_irqsave(&emc->lock, flags); > + tegra210_emc_set_clock(emc, config->value); > + emc->clkchange_time = ktime_get(); > + emc->last = timing; > + spin_unlock_irqrestore(&emc->lock, flags); > + > + return 0; > +} I'd suggest to check how much time invocation of ktime_get() takes, at least it came to a surprise to me in a case of the tegra-cpuidle driver. It may be well over the emc->clkchange_delay. ... > +static int tegra210_emc_probe(struct platform_device *pdev) > +{ ... > + emc->clkchange_delay = 100; > + emc->training_interval = 100; Not sure why these aren't a constant with the code.. ?