Re: Failure booting DragonBoard APQ8060 after mach-qcom introduction

[Srinivas Kandagatla <srinivas.kandagatla@linaro.org>]

Hi Linus,


On 11/08/14 13:49, Linus Walleye wrote:
> On Mon, Aug 11, 2014 at 1:42 PM, Linus Walleij <linus.walleij@linaro.org> wrote:
>> On Mon, Aug 11, 2014 at 1:21 PM, Linus Walleij <linus.walleij@linaro.org> wrote:
>>
>>> The symptom is that not even earlyprints come up if I put some
>>> printascii() in start_kernel.
>>
>> Bah that was me not realizing that the defaults for DEBUG_UART_PHYS
>> and DEBUG_UART_VIRT has to be set up properly... now I get the
>> earlyprints.
>>
>> It seems to hang in the gsbi driver probe, off to debug.
>
> It appears that this oneliner gets the kernel booting again:
>
> diff --git a/drivers/soc/qcom/qcom_gsbi.c b/drivers/soc/qcom/qcom_gsbi.c
> index 447458e696a9..1759a3c9140a 100644
> --- a/drivers/soc/qcom/qcom_gsbi.c
> +++ b/drivers/soc/qcom/qcom_gsbi.c
> @@ -57,7 +57,7 @@ static int gsbi_probe(struct platform_device *pdev)
>          /* make sure the gsbi control write is not reordered */
>          wmb();
>
> -       clk_disable_unprepare(hclk);
> +       //clk_disable_unprepare(hclk);
>
>          return of_platform_populate(pdev->dev.of_node, NULL, NULL, &pdev->dev);
>   }
>
> The kernel hangs during disable/unprepare of the hclk for the GSBI.
> Turning off hclk's could be dangerous if there are vital system
> components using the hclk which does not yet have a reference
> taken in the kernel, due to missing drivers or similar.
>

There is a patch to fix this 
http://www.spinics.net/lists/linux-arm-msm/msg09633.html

> Any ideas?

IMO, hclk is also used by the serial IP, disabling the clock while its 
being used by early printk would result in hang, I think that's what you 
are seeing.

--srini
>
> Yours,
> Linus Walleij
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