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![Viresh Kumar](/assets/img/avatar_default.png)
During cpufreq driver's registration, if the ->init() callback for all the CPUs fail then there is not much point in keeping the driver around as it will only account for more of unnecessary noise, for example cpufreq core will try to suspend/resume the driver which never got registered properly. The removal of such a driver is avoided if the driver carries the CPUFREQ_STICKY flag. This was added way back [1] in 2004 and perhaps no one should ever need it now. A lot of drivers do set this flag, probably because they just copied it from other drivers. This was added earlier for some platforms [2] because their cpufreq drivers were getting registered before the CPUs were registered with subsys framework. And hence they used to fail. The same isn't true anymore though. The current code flow in the kernel is: start_kernel() -> kernel_init() -> kernel_init_freeable() -> do_basic_setup() -> driver_init() -> cpu_dev_init() -> subsys_system_register() //For CPUs -> do_initcalls() -> cpufreq_register_driver() Clearly, the CPUs will always get registered with subsys framework before any cpufreq driver can get probed. Remove the flag and update the relevant drivers. Link: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/include/linux/cpufreq.h?id=7cc9f0d9a1ab04cedc60d64fd8dcf7df224a3b4d # [1] Link: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/arch/arm/mach-sa1100/cpu-sa1100.c?id=f59d3bbe35f6268d729f51be82af8325d62f20f5 # [2] Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
247 lines
5.9 KiB
C
247 lines
5.9 KiB
C
/*
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* drivers/cpufreq/spear-cpufreq.c
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*
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* CPU Frequency Scaling for SPEAr platform
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*
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* Copyright (C) 2012 ST Microelectronics
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* Deepak Sikri <deepak.sikri@st.com>
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*
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* This file is licensed under the terms of the GNU General Public
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* License version 2. This program is licensed "as is" without any
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* warranty of any kind, whether express or implied.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/clk.h>
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#include <linux/cpufreq.h>
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#include <linux/err.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/of_device.h>
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#include <linux/platform_device.h>
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#include <linux/slab.h>
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#include <linux/types.h>
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/* SPEAr CPUFreq driver data structure */
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static struct {
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struct clk *clk;
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unsigned int transition_latency;
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struct cpufreq_frequency_table *freq_tbl;
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u32 cnt;
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} spear_cpufreq;
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static struct clk *spear1340_cpu_get_possible_parent(unsigned long newfreq)
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{
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struct clk *sys_pclk;
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int pclk;
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/*
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* In SPEAr1340, cpu clk's parent sys clk can take input from
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* following sources
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*/
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const char *sys_clk_src[] = {
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"sys_syn_clk",
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"pll1_clk",
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"pll2_clk",
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"pll3_clk",
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};
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/*
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* As sys clk can have multiple source with their own range
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* limitation so we choose possible sources accordingly
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*/
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if (newfreq <= 300000000)
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pclk = 0; /* src is sys_syn_clk */
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else if (newfreq > 300000000 && newfreq <= 500000000)
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pclk = 3; /* src is pll3_clk */
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else if (newfreq == 600000000)
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pclk = 1; /* src is pll1_clk */
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else
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return ERR_PTR(-EINVAL);
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/* Get parent to sys clock */
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sys_pclk = clk_get(NULL, sys_clk_src[pclk]);
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if (IS_ERR(sys_pclk))
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pr_err("Failed to get %s clock\n", sys_clk_src[pclk]);
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return sys_pclk;
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}
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/*
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* In SPEAr1340, we cannot use newfreq directly because we need to actually
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* access a source clock (clk) which might not be ancestor of cpu at present.
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* Hence in SPEAr1340 we would operate on source clock directly before switching
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* cpu clock to it.
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*/
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static int spear1340_set_cpu_rate(struct clk *sys_pclk, unsigned long newfreq)
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{
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struct clk *sys_clk;
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int ret = 0;
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sys_clk = clk_get_parent(spear_cpufreq.clk);
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if (IS_ERR(sys_clk)) {
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pr_err("failed to get cpu's parent (sys) clock\n");
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return PTR_ERR(sys_clk);
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}
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/* Set the rate of the source clock before changing the parent */
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ret = clk_set_rate(sys_pclk, newfreq);
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if (ret) {
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pr_err("Failed to set sys clk rate to %lu\n", newfreq);
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return ret;
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}
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ret = clk_set_parent(sys_clk, sys_pclk);
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if (ret) {
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pr_err("Failed to set sys clk parent\n");
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return ret;
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}
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return 0;
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}
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static int spear_cpufreq_target(struct cpufreq_policy *policy,
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unsigned int index)
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{
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long newfreq;
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struct clk *srcclk;
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int ret, mult = 1;
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newfreq = spear_cpufreq.freq_tbl[index].frequency * 1000;
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if (of_machine_is_compatible("st,spear1340")) {
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/*
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* SPEAr1340 is special in the sense that due to the possibility
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* of multiple clock sources for cpu clk's parent we can have
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* different clock source for different frequency of cpu clk.
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* Hence we need to choose one from amongst these possible clock
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* sources.
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*/
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srcclk = spear1340_cpu_get_possible_parent(newfreq);
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if (IS_ERR(srcclk)) {
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pr_err("Failed to get src clk\n");
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return PTR_ERR(srcclk);
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}
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/* SPEAr1340: src clk is always 2 * intended cpu clk */
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mult = 2;
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} else {
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/*
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* src clock to be altered is ancestor of cpu clock. Hence we
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* can directly work on cpu clk
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*/
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srcclk = spear_cpufreq.clk;
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}
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newfreq = clk_round_rate(srcclk, newfreq * mult);
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if (newfreq <= 0) {
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pr_err("clk_round_rate failed for cpu src clock\n");
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return newfreq;
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}
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if (mult == 2)
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ret = spear1340_set_cpu_rate(srcclk, newfreq);
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else
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ret = clk_set_rate(spear_cpufreq.clk, newfreq);
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if (ret)
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pr_err("CPU Freq: cpu clk_set_rate failed: %d\n", ret);
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return ret;
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}
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static int spear_cpufreq_init(struct cpufreq_policy *policy)
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{
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policy->clk = spear_cpufreq.clk;
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cpufreq_generic_init(policy, spear_cpufreq.freq_tbl,
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spear_cpufreq.transition_latency);
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return 0;
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}
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static struct cpufreq_driver spear_cpufreq_driver = {
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.name = "cpufreq-spear",
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.flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK,
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.verify = cpufreq_generic_frequency_table_verify,
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.target_index = spear_cpufreq_target,
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.get = cpufreq_generic_get,
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.init = spear_cpufreq_init,
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.attr = cpufreq_generic_attr,
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};
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static int spear_cpufreq_probe(struct platform_device *pdev)
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{
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struct device_node *np;
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const struct property *prop;
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struct cpufreq_frequency_table *freq_tbl;
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const __be32 *val;
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int cnt, i, ret;
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np = of_cpu_device_node_get(0);
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if (!np) {
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pr_err("No cpu node found\n");
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return -ENODEV;
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}
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if (of_property_read_u32(np, "clock-latency",
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&spear_cpufreq.transition_latency))
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spear_cpufreq.transition_latency = CPUFREQ_ETERNAL;
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prop = of_find_property(np, "cpufreq_tbl", NULL);
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if (!prop || !prop->value) {
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pr_err("Invalid cpufreq_tbl\n");
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ret = -ENODEV;
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goto out_put_node;
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}
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cnt = prop->length / sizeof(u32);
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val = prop->value;
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freq_tbl = kcalloc(cnt + 1, sizeof(*freq_tbl), GFP_KERNEL);
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if (!freq_tbl) {
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ret = -ENOMEM;
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goto out_put_node;
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}
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for (i = 0; i < cnt; i++)
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freq_tbl[i].frequency = be32_to_cpup(val++);
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freq_tbl[i].frequency = CPUFREQ_TABLE_END;
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spear_cpufreq.freq_tbl = freq_tbl;
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of_node_put(np);
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spear_cpufreq.clk = clk_get(NULL, "cpu_clk");
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if (IS_ERR(spear_cpufreq.clk)) {
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pr_err("Unable to get CPU clock\n");
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ret = PTR_ERR(spear_cpufreq.clk);
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goto out_put_mem;
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}
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ret = cpufreq_register_driver(&spear_cpufreq_driver);
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if (!ret)
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return 0;
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pr_err("failed register driver: %d\n", ret);
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clk_put(spear_cpufreq.clk);
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out_put_mem:
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kfree(freq_tbl);
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return ret;
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out_put_node:
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of_node_put(np);
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return ret;
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}
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static struct platform_driver spear_cpufreq_platdrv = {
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.driver = {
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.name = "spear-cpufreq",
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},
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.probe = spear_cpufreq_probe,
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};
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module_platform_driver(spear_cpufreq_platdrv);
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MODULE_AUTHOR("Deepak Sikri <deepak.sikri@st.com>");
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MODULE_DESCRIPTION("SPEAr CPUFreq driver");
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MODULE_LICENSE("GPL");
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