Re: [PATCH 1/4] clk: tegra: Enable fuse clock on Tegra124

[Stephen Warren <swarren@wwwdotorg.org>]

On 10/2/19 5:04 AM, Thierry Reding wrote:
> On Tue, Oct 01, 2019 at 03:13:43PM -0600, Stephen Warren wrote:
>> From: Stephen Warren <swarren@nvidia.com>
>>
>> For a little over a year, U-Boot has configured the flow controller to
>> perform automatic RAM re-repair on off->on power transitions of the CPU
>> rail1]. This is mandatory for correct operation of Tegra124. However, RAM
>> re-repair relies on certain clocks, which the kernel must enable and
>> leave running. The fuse clock is one of those clocks. Enable this clock
>> so that LP1 power mode (system suspend) operates correctly.
>>
>> [1] 3cc7942a4ae5 ARM: tegra: implement RAM repair
>>
>> Reported-by: Jonathan Hunter <jonathanh@nvidia.com>
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Stephen Warren <swarren@nvidia.com>
>> ---
>>   drivers/clk/tegra/clk-tegra124.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/clk/tegra/clk-tegra124.c b/drivers/clk/tegra/clk-tegra124.c
>> index 0224fdc4766f..f53f6315c646 100644
>> --- a/drivers/clk/tegra/clk-tegra124.c
>> +++ b/drivers/clk/tegra/clk-tegra124.c
>> @@ -1291,6 +1291,7 @@ static struct tegra_clk_init_table common_init_table[] __initdata = {
>>   };
>>   
>>   static struct tegra_clk_init_table tegra124_init_table[] __initdata = {
>> +	{ TEGRA124_CLK_FUSE, -1, 0, 1 },
> 
> I think the correct way to do this these days is to mark the clock as
> CRITICAL. Not sure if there's an easy way to do that given that the
> clock init table doesn't allow storing flags.
> 
> Do you have any good ideas on how to achieve this with the critical flag
> instead of forcing the refcount to 1?
> 
> Perhaps something like the below would work?
 > ...

The following works for me; does this seem like a reasonable approach? 
It does set the critical flag for all SoCs, including any that don't 
require RAM re-repair. I'm not sure which do; I know it's more than just 
Tegra124, but I'm not sure how far back/forward the requirement goes.

> diff --git a/drivers/clk/tegra/clk-tegra-periph.c b/drivers/clk/tegra/clk-tegra-periph.c
> index 1ed85f120a1b..76dd91eebd13 100644
> --- a/drivers/clk/tegra/clk-tegra-periph.c
> +++ b/drivers/clk/tegra/clk-tegra-periph.c
> @@ -785,7 +785,7 @@ static struct tegra_periph_init_data gate_clks[] = {
>         GATE("ahbdma", "hclk", 33, 0, tegra_clk_ahbdma, 0),
>         GATE("apbdma", "pclk", 34, 0, tegra_clk_apbdma, 0),
>         GATE("kbc", "clk_32k", 36, TEGRA_PERIPH_ON_APB | TEGRA_PERIPH_NO_RESET, tegra_clk_kbc, 0),
> -       GATE("fuse", "clk_m", 39, TEGRA_PERIPH_ON_APB, tegra_clk_fuse, 0),
> +       GATE("fuse", "clk_m", 39, TEGRA_PERIPH_ON_APB, tegra_clk_fuse, CLK_IS_CRITICAL),
>         GATE("fuse_burn", "clk_m", 39, TEGRA_PERIPH_ON_APB, tegra_clk_fuse_burn, 0),
>         GATE("kfuse", "clk_m", 40, TEGRA_PERIPH_ON_APB, tegra_clk_kfuse, 0),
>         GATE("apbif", "clk_m", 107, TEGRA_PERIPH_ON_APB, tegra_clk_apbif, 0),

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