Re: [PATCH v3 15/15] usb: ohci-at91: fix possible hang chainloading barebox

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 16.02.24 14:15, Sascha Hauer wrote:
> On Thu, Feb 15, 2024 at 05:30:09PM +0100, Ahmad Fatoum wrote:
>> barebox, like Linux, will consider disabling parents when disabling a
>> child clock. In the AT91 OHCI driver ported to barebox from Linux, this
>> leads to the USB clock shutdown during device shutdown to propagate up
>> to PLLB, which is also disabled.
>>
>> On probe of the kernel driver, the USB clock rate is set to 48MHz, which
>> propagates up to the PLL, which is powered on again. In barebox, this clock
>> rate propagation does not happen and the PLL is only initially
>> configured in the first stage bootloader.
>>
>> This has the effect that chainloading barebox from within barebox will
>> hang as the first barebox disables PLLB on shutdown and the second
>> barebox never power it on.
>>
>> The proper solution would be to support propagation of clock rate change
>> requests, but till we have that, patch the driver, so only the immediate
>> clock is disabled and not its parents.
>>
>> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
>> ---
>> v3:
>>   - new patch
>> ---
>>  drivers/clk/clk.c            | 12 +++++++++---
>>  drivers/usb/host/ohci-at91.c | 13 +++++++++++--
>>  include/linux/clk.h          | 20 ++++++++++++++++++--
>>  3 files changed, 38 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
>> index d3f5d5e83880..03533b61df0a 100644
>> --- a/drivers/clk/clk.c
>> +++ b/drivers/clk/clk.c
>> @@ -66,7 +66,7 @@ int clk_enable(struct clk *clk)
>>  	return 0;
>>  }
>>  
>> -void clk_disable(struct clk *clk)
>> +void clk_disable_one(struct clk *clk)
>>  {
> 
> I don't like this very much as it screws up the enable counter of the
> clocks.
> 
> Cou could mark the PLL clock as critical or simply not disable the clock
> in the driver.

Ok, I will think about it. I will drop this from v2.

Thanks,
Ahmad

> 
> Sascha
> 
> 

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