Re: [PATCH v2 2/3] nvmem: qfprom: sc7280: Handle the additional power-domains vote

On 7/29/2021 9:37 PM, Doug Anderson wrote:

Hi,

On Thu, Jul 29, 2021 at 5:01 AM Rajendra Nayak [off-list ref] wrote:

quoted

On sc7280, to reliably blow fuses, we need an additional vote
on max performance state of 'MX' power-domain.
Add support for power-domain performance state voting in the
driver.

Signed-off-by: Rajendra Nayak <redacted>
---
  drivers/nvmem/qfprom.c | 26 ++++++++++++++++++++++++++
  1 file changed, 26 insertions(+)

diff --git a/drivers/nvmem/qfprom.c b/drivers/nvmem/qfprom.c
index 81fbad5..b5f27df 100644
--- a/drivers/nvmem/qfprom.c
+++ b/drivers/nvmem/qfprom.c

@@ -12,6 +12,8 @@
  #include <linux/mod_devicetable.h>
  #include <linux/nvmem-provider.h>
  #include <linux/platform_device.h>
+#include <linux/pm_domain.h>
+#include <linux/pm_runtime.h>
  #include <linux/property.h>
  #include <linux/regulator/consumer.h>

@@ -139,6 +141,9 @@ static void qfprom_disable_fuse_blowing(const struct qfprom_priv *priv,
  {
         int ret;

+       dev_pm_genpd_set_performance_state(priv->dev, 0);
+       pm_runtime_put(priv->dev);

To me it feels as if this should be at the end of the function rather
than the beginning. I guess it doesn't matter (?), but it feels wrong
that we have writes to the register space after we're don't a
pm_runtime_put().

Right, I was confused with this too when I saw that the other resources
(regulator/clocks) were also turned off before we write into the
register space. And then looking into the driver I realized its perhaps because
the resources are needed only for the 'raw' writes and the 'conf'
read/writes can happen regardless. I'll just fix that up and put the register
writes before we really turn off any resources to avoid confusion.

quoted

@@ -420,6 +440,12 @@ static int qfprom_probe(struct platform_device *pdev)
                         econfig.reg_write = qfprom_reg_write;
         }

+       ret = devm_add_action_or_reset(dev, qfprom_runtime_disable, dev);
+       if (ret)
+               return ret;
+
+       pm_runtime_enable(dev);
+

Swap the order of the two. IOW first pm_runtime_enable(), then
devm_add_action_or_reset(). Specifically the "_or_reset" means that if
you fail to add the action (AKA devm_add_action() fails to allocate
the tiny amount of memory it needs) it will actually _call_ the
action. 

Ah, I didn't know that, thanks, I'll fix the order up and repost.

That means that in your code if the memory allocation fails
you'll call pm_runtime_disable() without the corresponding
pm_runtime_enable().


Other than those two issues this looks good to me. Feel free to add my
Reviewed-by when you fix them.

Thanks.

-Doug

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