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fa9eb32418
since commit 31964ffebb ("tty: serial: msm: Remove direct access to GSBI")'
serial hangs if earlyprintk are enabled.
This hang is noticed only when the GSBI driver is probed and all the
earlyprintks before gsbi probe are seen on the console.
The reason why it hangs is because GSBI driver disables hclk in its
probe function without realizing that the serial IP might be in use by
a bootconsole. As gsbi driver disables the clock in probe the
bootconsole locks up.
Turning off hclk's could be dangerous if there are system components
like earlyprintk using the hclk.
This patch fixes the issue by delegating the clock management to
probe and remove functions in gsbi rather than disabling the clock in probe.
More detailed problem description can be found here:
http://www.spinics.net/lists/linux-arm-msm/msg10589.html
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>
106 lines
2.6 KiB
C
106 lines
2.6 KiB
C
/*
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* Copyright (c) 2014, The Linux foundation. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License rev 2 and
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* only rev 2 as published by the free Software foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or fITNESS fOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <linux/clk.h>
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#include <linux/err.h>
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#include <linux/io.h>
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#include <linux/module.h>
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#include <linux/of.h>
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#include <linux/of_platform.h>
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#include <linux/platform_device.h>
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#define GSBI_CTRL_REG 0x0000
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#define GSBI_PROTOCOL_SHIFT 4
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struct gsbi_info {
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struct clk *hclk;
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u32 mode;
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u32 crci;
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};
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static int gsbi_probe(struct platform_device *pdev)
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{
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struct device_node *node = pdev->dev.of_node;
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struct resource *res;
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void __iomem *base;
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struct gsbi_info *gsbi;
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gsbi = devm_kzalloc(&pdev->dev, sizeof(*gsbi), GFP_KERNEL);
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if (!gsbi)
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return -ENOMEM;
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res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
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base = devm_ioremap_resource(&pdev->dev, res);
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if (IS_ERR(base))
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return PTR_ERR(base);
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if (of_property_read_u32(node, "qcom,mode", &gsbi->mode)) {
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dev_err(&pdev->dev, "missing mode configuration\n");
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return -EINVAL;
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}
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/* not required, so default to 0 if not present */
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of_property_read_u32(node, "qcom,crci", &gsbi->crci);
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dev_info(&pdev->dev, "GSBI port protocol: %d crci: %d\n",
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gsbi->mode, gsbi->crci);
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gsbi->hclk = devm_clk_get(&pdev->dev, "iface");
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if (IS_ERR(gsbi->hclk))
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return PTR_ERR(gsbi->hclk);
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clk_prepare_enable(gsbi->hclk);
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writel_relaxed((gsbi->mode << GSBI_PROTOCOL_SHIFT) | gsbi->crci,
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base + GSBI_CTRL_REG);
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/* make sure the gsbi control write is not reordered */
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wmb();
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platform_set_drvdata(pdev, gsbi);
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return of_platform_populate(node, NULL, NULL, &pdev->dev);
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}
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static int gsbi_remove(struct platform_device *pdev)
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{
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struct gsbi_info *gsbi = platform_get_drvdata(pdev);
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clk_disable_unprepare(gsbi->hclk);
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return 0;
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}
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static const struct of_device_id gsbi_dt_match[] = {
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{ .compatible = "qcom,gsbi-v1.0.0", },
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{ },
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};
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MODULE_DEVICE_TABLE(of, gsbi_dt_match);
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static struct platform_driver gsbi_driver = {
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.driver = {
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.name = "gsbi",
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.owner = THIS_MODULE,
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.of_match_table = gsbi_dt_match,
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},
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.probe = gsbi_probe,
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.remove = gsbi_remove,
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};
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module_platform_driver(gsbi_driver);
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MODULE_AUTHOR("Andy Gross <agross@codeaurora.org>");
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MODULE_DESCRIPTION("QCOM GSBI driver");
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MODULE_LICENSE("GPL v2");
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