lkml.org 
[lkml]   [2013]   [Nov]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] ARM: tegra: properly use FUSE clock
On 11/18/2013 08:43 PM, Thierry Reding wrote:
> * PGP Signed by an unknown key
>
> On Mon, Nov 18, 2013 at 07:40:47PM +0900, Alexandre Courbot wrote:
>> FUSE clock is enabled by most bootloaders, but we cannot expect it to be
>> on in all contexts (e.g. kexec).
>>
>> This patch adds a FUSE clkdev to all Tegra platforms and makes sure
>> it is enabled before touching FUSE registers. tegra_init_fuse() is
>> invoked during very early boot and thus cannot rely on the clock
>> framework ; therefore the FUSE clock is forcibly enabled using a
>> register write in that function, and remains that way until the
>> clock framework can be used.
>>
>> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
>> ---
>> arch/arm/mach-tegra/fuse.c | 41 +++++++++++++++++++++++++++++++++++++++-
>> drivers/clk/tegra/clk-tegra114.c | 1 +
>> drivers/clk/tegra/clk-tegra124.c | 1 +
>> drivers/clk/tegra/clk-tegra20.c | 1 +
>
> Isn't this missing the clock driver changes for Tegra30? Ah... Tegra30
> already has this clock defined. I wonder why only Tegra30 has it. grep
> says that fuse-tegra isn't used by any drivers, which also indicates
> that perhaps we don't need the .dev_id in the first place. We should be
> able to get by with just the .con_id = "fuse".

Will fix that.

> Also are there any reasons to keep this in one single patch? Since none
> of the fuse clocks are used yet, I think the clock changes could be a
> separate patch that can go in through the clock tree. And there isn't
> even a hard runtime dependency, since if the Tegra changes were to go in
> without the clock changes, then the fallback code in this patch should
> still turn the clock on properly. It just might not be turned off again,
> but isn't that something we can live with for a short period of time? I
> think perhaps that could even be improved, see further below.
>
> I've added Mike on Cc, he'll need to either take the patch in through
> his tree or Ack this one, so he needs to see it eventually.

I will split the change into two patches - at first I thought it would
not be worth the trouble, but I overlooked the fact this needed to go
through the clock source tree.

>
>> 4 files changed, 43 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/mach-tegra/fuse.c b/arch/arm/mach-tegra/fuse.c
>> index 9a4e910c3796..3b9191b930b5 100644
>> --- a/arch/arm/mach-tegra/fuse.c
>> +++ b/arch/arm/mach-tegra/fuse.c
>> @@ -22,6 +22,7 @@
>> #include <linux/io.h>
>> #include <linux/export.h>
>> #include <linux/random.h>
>> +#include <linux/clk.h>
>> #include <linux/tegra-soc.h>
>>
>> #include "fuse.h"
>> @@ -54,6 +55,7 @@ int tegra_cpu_speedo_id; /* only exist in Tegra30 and later */
>> int tegra_soc_speedo_id;
>> enum tegra_revision tegra_revision;
>>
>> +static struct clk *fuse_clk;
>> static int tegra_fuse_spare_bit;
>> static void (*tegra_init_speedo_data)(void);
>>
>> @@ -77,6 +79,22 @@ static const char *tegra_revision_name[TEGRA_REVISION_MAX] = {
>> [TEGRA_REVISION_A04] = "A04",
>> };
>>
>> +static void tegra_fuse_enable_clk(void)
>> +{
>> + if (IS_ERR(fuse_clk))
>> + fuse_clk = clk_get_sys("fuse-tegra", "fuse");
>> + if (IS_ERR(fuse_clk))
>> + return;
>
> Perhaps instead of just returning here, this should actually be where
> the code to enable the clock should go.
>
>> + clk_prepare_enable(fuse_clk);
>> +}
>> +
>> +static void tegra_fuse_disable_clk(void)
>> +{
>> + if (IS_ERR(fuse_clk))
>> + return;
>
> And this is where we could disable it again. That way we should get
> equal functionality in both cases.

What Stephen said, basically - but let me address that in the other mail.

Thanks for the review!
Alex.



\
 
 \ /
  Last update: 2013-11-19 06:21    [W:0.059 / U:11.988 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site