On Thu, Nov 01, 2018 at 02:52:29AM +0100, Marcel Ziswiler wrote:
> From: Marcel Ziswiler <marcel.ziswiler@xxxxxxxxxxx>
>
> As UARTB and VFIR share their clock enable bit it is rather unwise for
> the kernel to turn off the VFIR one should that be unused (and
> potentially vice versa but so far there anyway is no VFIR driver).
>
> Without this patch trying to use UARTB with the regular 8250 driver
> will freeze as soon as ttyS1 is accessed after boot. Luckily, using the
> high-speed Tegra serial driver won't exhibit the issue as clocks are
> dynamically enabled/disabled on every access.
>
> This has been reproduced both on Apalis T30 as well as Apalis TK1 but
> may be an issue on all Tegra UARTB's which share the clock enable with
> VFIR.
>
Ah.. the correct fix for this is to initialize the enable_refcnt based on the
hw state. This is done in 9619dba8325fce098bbc9ee2911d1b0150fec0c9 for
periph gate clocks, but obviously also applies to normal periph clocks.
Peter.
> Reported-by: Kory Swain <kory.swain@xxxxxxxxxxxxxxxx>
> Signed-off-by: Marcel Ziswiler <marcel.ziswiler@xxxxxxxxxxx>
>
> ---
>
> drivers/clk/tegra/clk-tegra-periph.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/clk/tegra/clk-tegra-periph.c b/drivers/clk/tegra/clk-tegra-periph.c
> index cc5275ec2c01..116c74340fb7 100644
> --- a/drivers/clk/tegra/clk-tegra-periph.c
> +++ b/drivers/clk/tegra/clk-tegra-periph.c
> @@ -668,7 +668,7 @@ static struct tegra_periph_init_data periph_clks[] = {
> MUX("hda", mux_pllp_pllc_clkm, CLK_SOURCE_HDA, 125, TEGRA_PERIPH_ON_APB, tegra_clk_hda_8),
> MUX("hda2codec_2x", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_HDA2CODEC_2X, 111, TEGRA_PERIPH_ON_APB, tegra_clk_hda2codec_2x),
> MUX8("hda2codec_2x", mux_pllp_pllc_plla_clkm, CLK_SOURCE_HDA2CODEC_2X, 111, TEGRA_PERIPH_ON_APB, tegra_clk_hda2codec_2x_8),
> - MUX("vfir", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_VFIR, 7, TEGRA_PERIPH_ON_APB, tegra_clk_vfir),
> + MUX_FLAGS("vfir", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_VFIR, 7, TEGRA_PERIPH_ON_APB, tegra_clk_vfir, CLK_IGNORE_UNUSED),
> MUX("sdmmc1", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_SDMMC1, 14, TEGRA_PERIPH_ON_APB, tegra_clk_sdmmc1),
> MUX("sdmmc2", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_SDMMC2, 9, TEGRA_PERIPH_ON_APB, tegra_clk_sdmmc2),
> MUX("sdmmc3", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_SDMMC3, 69, TEGRA_PERIPH_ON_APB, tegra_clk_sdmmc3),
> --
> 2.14.5
>
