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serial: 8250_mtk: Simplify clock sequencing and runtime PM
The 8250_mtk driver's runtime PM support has some issues:
- The bus clock is enabled (through runtime PM callback) later than a
register write
- runtime PM resume callback directly called in probe, but no
pm_runtime_set_active() call is present
- UART PM function calls the callbacks directly, _and_ calls runtime
PM API
- runtime PM callbacks try to do reference counting, adding yet another
count between runtime PM and clocks
This fragile setup worked in a way, but broke recently with runtime PM
support added to the serial core. The system would hang when the UART
console was probed and brought up.
Tony provided some potential fixes [1][2], though they were still a bit
complicated. The 8250_dw driver, which the 8250_mtk driver might have
been based on, has a similar structure but simpler runtime PM usage.
Simplify clock sequencing and runtime PM support in the 8250_mtk driver.
Specifically, the clock is acquired enabled and assumed to be active,
unless toggled through runtime PM suspend/resume. Reference counting is
removed and left to the runtime PM core. The serial pm function now
only calls the runtime PM API.
[1] https://lore.kernel.org/linux-serial/20230602092701.GP14287@atomide.com/
[2] https://lore.kernel.org/linux-serial/20230605061511.GW14287@atomide.com/
Fixes: 84a9582fd2
("serial: core: Start managing serial controllers to enable runtime PM")
Suggested-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Tony Lindgren <tony@atomide.com>
Message-ID: <20230606091747.2031168-1-wenst@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
643662d12b
commit
b6c7ff2693
1 changed files with 10 additions and 40 deletions
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@ -431,12 +431,7 @@ static int __maybe_unused mtk8250_runtime_suspend(struct device *dev)
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while
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(serial_in(up, MTK_UART_DEBUG0));
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if (data->clk_count == 0U) {
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dev_dbg(dev, "%s clock count is 0\n", __func__);
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} else {
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clk_disable_unprepare(data->bus_clk);
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data->clk_count--;
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}
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clk_disable_unprepare(data->bus_clk);
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return 0;
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}
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@ -444,19 +439,8 @@ static int __maybe_unused mtk8250_runtime_suspend(struct device *dev)
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static int __maybe_unused mtk8250_runtime_resume(struct device *dev)
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{
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struct mtk8250_data *data = dev_get_drvdata(dev);
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int err;
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if (data->clk_count > 0U) {
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dev_dbg(dev, "%s clock count is %d\n", __func__,
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data->clk_count);
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} else {
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err = clk_prepare_enable(data->bus_clk);
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if (err) {
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dev_warn(dev, "Can't enable bus clock\n");
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return err;
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}
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data->clk_count++;
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}
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clk_prepare_enable(data->bus_clk);
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return 0;
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}
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@ -465,14 +449,12 @@ static void
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mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
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{
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if (!state)
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if (!mtk8250_runtime_resume(port->dev))
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pm_runtime_get_sync(port->dev);
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pm_runtime_get_sync(port->dev);
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serial8250_do_pm(port, state, old);
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if (state)
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if (!pm_runtime_put_sync_suspend(port->dev))
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mtk8250_runtime_suspend(port->dev);
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pm_runtime_put_sync_suspend(port->dev);
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}
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#ifdef CONFIG_SERIAL_8250_DMA
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@ -504,7 +486,7 @@ static int mtk8250_probe_of(struct platform_device *pdev, struct uart_port *p,
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return 0;
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}
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data->bus_clk = devm_clk_get(&pdev->dev, "bus");
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data->bus_clk = devm_clk_get_enabled(&pdev->dev, "bus");
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if (IS_ERR(data->bus_clk))
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return PTR_ERR(data->bus_clk);
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@ -587,25 +569,16 @@ static int mtk8250_probe(struct platform_device *pdev)
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platform_set_drvdata(pdev, data);
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pm_runtime_enable(&pdev->dev);
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err = mtk8250_runtime_resume(&pdev->dev);
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if (err)
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goto err_pm_disable;
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data->line = serial8250_register_8250_port(&uart);
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if (data->line < 0) {
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err = data->line;
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goto err_pm_disable;
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}
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if (data->line < 0)
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return data->line;
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data->rx_wakeup_irq = platform_get_irq_optional(pdev, 1);
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pm_runtime_set_active(&pdev->dev);
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pm_runtime_enable(&pdev->dev);
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return 0;
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err_pm_disable:
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pm_runtime_disable(&pdev->dev);
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return err;
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}
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static int mtk8250_remove(struct platform_device *pdev)
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@ -619,9 +592,6 @@ static int mtk8250_remove(struct platform_device *pdev)
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pm_runtime_disable(&pdev->dev);
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pm_runtime_put_noidle(&pdev->dev);
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if (!pm_runtime_status_suspended(&pdev->dev))
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mtk8250_runtime_suspend(&pdev->dev);
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return 0;
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}
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