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    Subject[PATCH 5.5 018/119] drm/exynos: dsi: fix workaround for the legacy clock name
    Date
    From: Marek Szyprowski <m.szyprowski@samsung.com>

    [ Upstream commit c0fd99d659ba5582e09625c7a985d63fc2ca74b5 ]

    Writing to the built-in strings arrays doesn't work if driver is loaded
    as kernel module. This is also considered as a bad pattern. Fix this by
    adding a call to clk_get() with legacy clock name. This fixes following
    kernel oops if driver is loaded as module:

    Unable to handle kernel paging request at virtual address bf047978
    pgd = (ptrval)
    [bf047978] *pgd=59344811, *pte=5903c6df, *ppte=5903c65f
    Internal error: Oops: 80f [#1] SMP ARM
    Modules linked in: mc exynosdrm(+) analogix_dp rtc_s3c exynos_ppmu i2c_gpio
    CPU: 1 PID: 212 Comm: systemd-udevd Not tainted 5.6.0-rc2-next-20200219 #326
    videodev: Linux video capture interface: v2.00
    Hardware name: Samsung Exynos (Flattened Device Tree)
    PC is at exynos_dsi_probe+0x1f0/0x384 [exynosdrm]
    LR is at exynos_dsi_probe+0x1dc/0x384 [exynosdrm]
    ...
    Process systemd-udevd (pid: 212, stack limit = 0x(ptrval))
    ...
    [<bf03cf14>] (exynos_dsi_probe [exynosdrm]) from [<c09b1ca0>] (platform_drv_probe+0x6c/0xa4)
    [<c09b1ca0>] (platform_drv_probe) from [<c09afcb8>] (really_probe+0x210/0x350)
    [<c09afcb8>] (really_probe) from [<c09aff74>] (driver_probe_device+0x60/0x1a0)
    [<c09aff74>] (driver_probe_device) from [<c09b0254>] (device_driver_attach+0x58/0x60)
    [<c09b0254>] (device_driver_attach) from [<c09b02dc>] (__driver_attach+0x80/0xbc)
    [<c09b02dc>] (__driver_attach) from [<c09ade00>] (bus_for_each_dev+0x68/0xb4)
    [<c09ade00>] (bus_for_each_dev) from [<c09aefd8>] (bus_add_driver+0x130/0x1e8)
    [<c09aefd8>] (bus_add_driver) from [<c09b0d64>] (driver_register+0x78/0x110)
    [<c09b0d64>] (driver_register) from [<bf038558>] (exynos_drm_init+0xe8/0x11c [exynosdrm])
    [<bf038558>] (exynos_drm_init [exynosdrm]) from [<c0302fa8>] (do_one_initcall+0x50/0x220)
    [<c0302fa8>] (do_one_initcall) from [<c03dd02c>] (do_init_module+0x60/0x210)
    [<c03dd02c>] (do_init_module) from [<c03dbf44>] (load_module+0x1c0c/0x2310)
    [<c03dbf44>] (load_module) from [<c03dc85c>] (sys_finit_module+0xac/0xbc)
    [<c03dc85c>] (sys_finit_module) from [<c0301000>] (ret_fast_syscall+0x0/0x54)
    Exception stack(0xd979bfa8 to 0xd979bff0)
    ...
    ---[ end trace db16efe05faab470 ]---

    Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
    Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
    Signed-off-by: Inki Dae <inki.dae@samsung.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/gpu/drm/exynos/exynos_drm_dsi.c | 7 ++++---
    1 file changed, 4 insertions(+), 3 deletions(-)

    diff --git a/drivers/gpu/drm/exynos/exynos_drm_dsi.c b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
    index 8d880012b5876..0f6497670e29d 100644
    --- a/drivers/gpu/drm/exynos/exynos_drm_dsi.c
    +++ b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
    @@ -1766,9 +1766,10 @@ static int exynos_dsi_probe(struct platform_device *pdev)
    dsi->clks[i] = devm_clk_get(dev, clk_names[i]);
    if (IS_ERR(dsi->clks[i])) {
    if (strcmp(clk_names[i], "sclk_mipi") == 0) {
    - strcpy(clk_names[i], OLD_SCLK_MIPI_CLK_NAME);
    - i--;
    - continue;
    + dsi->clks[i] = devm_clk_get(dev,
    + OLD_SCLK_MIPI_CLK_NAME);
    + if (!IS_ERR(dsi->clks[i]))
    + continue;
    }

    dev_info(dev, "failed to get the clock: %s\n",
    --
    2.20.1


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