Hi Ulf,
On 2017-03-13 14:31, Ulf Hansson wrote:
On 25 January 2017 at 12:53, Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> wrote:
Add runtime pm support for all clock controller units (CMU), which belongs
to power domains and require special handling during on/off operations.
Typically special values has to be written to MUX registers to change
internal clocks parents to OSC clock before turning power off. During such
operation all clocks, which enters CMU has to be enabled to let MUX to
stabilize. Also for each CMU there is one special parent clock, which has
to be enabled all the time when any access to CMU registers is done.
This patch solves most of the mysterious external abort and freeze issues
caused by a lack of proper parent CMU clock enabled or incorrect turn off
procedure.
Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
---
Thanks for your review!
[...]
--- a/drivers/clk/samsung/clk-exynos5433.c
+++ b/drivers/clk/samsung/clk-exynos5433.c
@@ -9,9 +9,14 @@
* Common Clock Framework support for Exynos5443 SoC.
*/
+#include <linux/clk.h>
#include <linux/clk-provider.h>
#include <linux/of.h>
#include <linux/of_address.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/slab.h>
#include <dt-bindings/clock/exynos5433.h>
[...]
+struct exynos5433_cmu_data {
+ struct samsung_clk_provider ctx;
+
+ struct samsung_clk_reg_dump *clk_save;
+ unsigned int nr_clk_save;
+ const struct samsung_clk_reg_dump *clk_suspend;
+ unsigned int nr_clk_suspend;
+
+ struct clk *clk;
+ struct clk **pclks;
+ int nr_pclks;
+};
+
+static int exynos5433_cmu_suspend(struct device *dev)
+{
+ struct exynos5433_cmu_data *data = dev_get_drvdata(dev);
+ int i;
+
+ samsung_clk_save(data->ctx.reg_base, data->clk_save,
+ data->nr_clk_save);
+
+ for (i = 0; i < data->nr_pclks; i++)
+ clk_enable(data->pclks[i]);
+
+ samsung_clk_restore(data->ctx.reg_base, data->clk_suspend,
+ data->nr_clk_suspend);
+
+ for (i = 0; i < data->nr_pclks; i++)
+ clk_disable(data->pclks[i]);
+
+ clk_disable(data->clk);
+
+ return 0;
+}
+
+static int exynos5433_cmu_resume(struct device *dev)
+{
+ struct exynos5433_cmu_data *data = dev_get_drvdata(dev);
+ int i;
+
+ clk_enable(data->clk);
+
+ for (i = 0; i < data->nr_pclks; i++)
+ clk_enable(data->pclks[i]);
+
+ samsung_clk_restore(data->ctx.reg_base, data->clk_save,
+ data->nr_clk_save);
+
+ for (i = 0; i < data->nr_pclks; i++)
+ clk_disable(data->pclks[i]);
+
+ return 0;
+}
+
+static int __init exynos5433_cmu_probe(struct platform_device *pdev)
+{
+ const struct samsung_cmu_info *info;
+ struct exynos5433_cmu_data *data;
+ struct samsung_clk_provider *ctx;
+ struct device *dev = &pdev->dev;
+ struct resource *res;
+ void __iomem *reg_base;
+ struct clk **clk_table;
+ int i;
+
+ info = of_device_get_match_data(dev);
+
+ data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+ ctx = &data->ctx;
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ reg_base = devm_ioremap_resource(dev, res);
+ if (!reg_base) {
+ dev_err(dev, "failed to map registers\n");
+ return -ENOMEM;
+ }
+
+ clk_table = devm_kcalloc(dev, info->nr_clk_ids, sizeof(struct clk *),
+ GFP_KERNEL);
+ if (!clk_table)
+ return -ENOMEM;
+
+ for (i = 0; i < info->nr_clk_ids; ++i)
+ clk_table[i] = ERR_PTR(-ENOENT);
+
+ ctx->clk_data.clks = clk_table;
+ ctx->clk_data.clk_num = info->nr_clk_ids;
+ ctx->reg_base = reg_base;
+ ctx->dev = dev;
+ spin_lock_init(&ctx->lock);
+
+ data->clk_save = samsung_clk_alloc_reg_dump(info->clk_regs,
+ info->nr_clk_regs);
+ data->nr_clk_save = info->nr_clk_regs;
+ data->clk_suspend = info->suspend_regs;
+ data->nr_clk_suspend = info->nr_suspend_regs;
+ data->nr_pclks = of_count_phandle_with_args(dev->of_node, "clocks",
+ "#clock-cells");
+ if (data->nr_pclks > 0) {
+ data->pclks = devm_kcalloc(dev, sizeof(struct clk *),
+ data->nr_pclks, GFP_KERNEL);
+
+ for (i = 0; i < data->nr_pclks; i++) {
+ struct clk *clk = of_clk_get(dev->of_node, i);
+
+ if (IS_ERR(clk))
+ return PTR_ERR(clk);
+ data->pclks[i] = clk;
+ }
+ }
+
+ /*
+ * Prepare all parent clocks here to avoid potential deadlock caused
+ * by global clock "prepare lock" grabbed by runtime pm callbacks
+ * from pm workers.
+ */
I don't understand why this potentially could cause a deadlock. Can
you please elaborate.
This deadlock was caused by using pm_runtime_put() in the clk core, but
after switching to pm_runtime_put_sync() it's gone. While tracking this
issue I also found another possible deadlock related to device_links.
I will send a separate patch for it.
To me, I think you should be fine doing clk_prepare_enable() and
clk_disable_unprepare() from exynos5433_cmu_suspend|resume(), but I
may be missing something.
+ for (i = 0; i < data->nr_pclks; i++)
+ clk_prepare(data->pclks[i]);
+
+ if (info->clk_name)
+ data->clk = clk_get(dev, info->clk_name);
+ clk_prepare_enable(data->clk);
+
+ platform_set_drvdata(pdev, data);
+
+ /*
+ * Enable runtime pm here, so clock core with use runtime pm for all
+ * registered clocks. Additionally call pm_runtime_get_sync to ensure
+ * that clock core will not runtime suspend our clock controller in
+ * the middle of clock registration (clock core might call runtime pm
+ * on newly registered clocks, for example to recalculate clock rate).
+ */
Instead of the rather confusing comment about the call to
pm_runtime_get_sync(), let's instead state that we increase the
runtime PM usage count during the clock registration, to avoid the
clock core from runtime suspending the device.
In other words, before calling pm_runtime_set_active(), add a call
pm_runtime_get_noresume() and then remove the latter call to
pm_runtime_get_sync().
Thanks for the hint!
+ pm_runtime_set_active(dev);
+ pm_runtime_enable(dev);
+ pm_runtime_get_sync(dev);
+
+ if (info->pll_clks)
+ samsung_clk_register_pll(ctx, info->pll_clks, info->nr_pll_clks,
+ reg_base);
+ if (info->mux_clks)
+ samsung_clk_register_mux(ctx, info->mux_clks,
+ info->nr_mux_clks);
+ if (info->div_clks)
+ samsung_clk_register_div(ctx, info->div_clks,
+ info->nr_div_clks);
+ if (info->gate_clks)
+ samsung_clk_register_gate(ctx, info->gate_clks,
+ info->nr_gate_clks);
+ if (info->fixed_clks)
+ samsung_clk_register_fixed_rate(ctx, info->fixed_clks,
+ info->nr_fixed_clks);
+ if (info->fixed_factor_clks)
+ samsung_clk_register_fixed_factor(ctx, info->fixed_factor_clks,
+ info->nr_fixed_factor_clks);
+
+ samsung_clk_of_add_provider(dev->of_node, ctx);
+ pm_runtime_put(dev);
+
+ return 0;
+}
[...]
Kind regards
Uffe
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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