linux-kernel - RE: [PATCH 3/3] mmc: sdhci-of-arasan: Add support for ZynqMP Platform Tap Delays Setup

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Date:   Thu, 20 Jun 2019 08:14:02 +0000
From:   Manish Narani <MNARANI@...inx.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
CC:     Michal Simek <michals@...inx.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Rajan Vaja <RAJANV@...inx.com>, Jolly Shah <JOLLYS@...inx.com>,
        Nava kishore Manne <navam@...inx.com>,
        Olof Johansson <olof@...om.net>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH 3/3] mmc: sdhci-of-arasan: Add support for ZynqMP Platform
 Tap Delays Setup

Hi Uffe,


> -----Original Message-----
> From: Ulf Hansson <ulf.hansson@...aro.org>
> Sent: Wednesday, June 19, 2019 7:09 PM
> To: Manish Narani <MNARANI@...inx.com>
> Cc: Michal Simek <michals@...inx.com>; Rob Herring <robh+dt@...nel.org>;
> Mark Rutland <mark.rutland@....com>; Adrian Hunter
> <adrian.hunter@...el.com>; Rajan Vaja <RAJANV@...inx.com>; Jolly Shah
> <JOLLYS@...inx.com>; Nava kishore Manne <navam@...inx.com>; Olof
> Johansson <olof@...om.net>; linux-mmc@...r.kernel.org; DTML
> <devicetree@...r.kernel.org>; Linux Kernel Mailing List <linux-
> kernel@...r.kernel.org>; Linux ARM <linux-arm-kernel@...ts.infradead.org>
> Subject: Re: [PATCH 3/3] mmc: sdhci-of-arasan: Add support for ZynqMP
> Platform Tap Delays Setup
> 
> On Wed, 19 Jun 2019 at 10:40, Manish Narani <MNARANI@...inx.com> wrote:
> >
> > Hi Uffe,
> >
> >
> > > -----Original Message-----
> > > From: Ulf Hansson <ulf.hansson@...aro.org>
> > > Sent: Monday, June 17, 2019 5:51 PM
> > [...]
> > >
> > > The "const struct zynqmp_eemi_ops *eemi_ops; should then be moved into
> > > a clock provider specific struct, which is assigned when calling
> > > sdhci_arasan_register_sdclk. I understand that all the clock data is
> > > folded into struct sdhci_arasan_data today, but I think that should be
> > > moved into a "sub-struct" for the clock specifics.
> > >
> > > Moreover, when registering the clock, we should convert from using
> > > devm_clk_register() into devm_clk_hw_register() as the first one is
> > > now deprecated.
> >
> > Just a query here:
> > When we switch to using devm_clk_hw_register() here, it will register the
> clk_hw and return int.
> > Is there a way we can get the clk (related to the clk_hw registered) from the
> > clock framework?
> > I am asking this because we will need that clk pointer while calling
> clk_set_phase() function.
> 
> I assume devm_clk_get() should work fine?

This clock does not come through ZynqMP Clock framework. We are initializing it in this 'sdhci-of-arasan' driver and getting only the clock name from "clock_output_names" property. So I think devm_clk_get() will not work here for our case.
I have gone through the clock framework and I found one function which may be used to create clock from clock hw, that is ' clk_hw_create_clk()' which can be used from our driver, however this needs change in the clock framework as below :

---
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index aa51756..4dc69ff 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -3420,6 +3420,7 @@ struct clk *clk_hw_create_clk(struct device *dev, struct clk_hw *hw,
 
        return clk;
 }
+EXPORT_SYMBOL_GPL(clk_hw_create_clk);
 
 static int clk_cpy_name(const char **dst_p, const char *src, bool must_exist)
 {
diff --git a/drivers/clk/clk.h b/drivers/clk/clk.h
index d8400d6..2319899 100644
--- a/drivers/clk/clk.h
+++ b/drivers/clk/clk.h
@@ -22,17 +22,9 @@ static inline struct clk_hw *of_clk_get_hw(struct device_node *np,
 struct clk_hw *clk_find_hw(const char *dev_id, const char *con_id);
 
 #ifdef CONFIG_COMMON_CLK
-struct clk *clk_hw_create_clk(struct device *dev, struct clk_hw *hw,
-                             const char *dev_id, const char *con_id);
 void __clk_put(struct clk *clk);
 #else
 /* All these casts to avoid ifdefs in clkdev... */
-static inline struct clk *
-clk_hw_create_clk(struct device *dev, struct clk_hw *hw, const char *dev_id,
-                 const char *con_id)
-{
-       return (struct clk *)hw;
-}
 static struct clk_hw *__clk_get_hw(struct clk *clk)
 {
        return (struct clk_hw *)clk;
diff --git a/include/linux/clk.h b/include/linux/clk.h
index f689fc5..d3f60fe 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -18,6 +18,7 @@
 
 struct device;
 struct clk;
+struct clk_hw;
 struct device_node;
 struct of_phandle_args;
 
@@ -934,4 +935,15 @@ static inline struct clk *of_clk_get_from_provider(struct of_phandle_args *clksp
 }
 #endif
 
+#ifdef CONFIG_COMMON_CLK
+struct clk *clk_hw_create_clk(struct device *dev, struct clk_hw *hw,
+                             const char *dev_id, const char *con_id);
+#else
+static inline struct clk *
+clk_hw_create_clk(struct device *dev, struct clk_hw *hw, const char *dev_id,
+                 const char *con_id)
+{
+       return (struct clk *)hw;
+}
+#endif
 #endif
---

This change should help other drivers (outside 'drivers/clk/') as well for getting the clock created from clk_hw.
Is this fine to do?

Thanks,
Manish