Message-ID: <20220409045952.3h4jkzkgziea4ysh@mobilestation>
Date:   Sat, 9 Apr 2022 07:59:52 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>
Cc:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Hans de Goede <hdegoede@...hat.com>,
        Jens Axboe <axboe@...nel.dk>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Rob Herring <robh+dt@...nel.org>, linux-ide@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 05/21] ata: libahci_platform: Convert to using devm bulk
 clocks API

On Thu, Mar 24, 2022 at 10:29:01AM +0900, Damien Le Moal wrote:
> On 3/24/22 09:16, Serge Semin wrote:
> > In order to simplify the clock-related code there is a way to convert the
> > current fixed clocks array into using the common bulk clocks kernel API
> > with dynamic set of the clock handlers and device-managed clock-resource
> > tracking. It's a bit tricky due to the complication coming from the
> > requirement to support the platforms (da850, spear13xx) with the
> > non-OF-based clock source, but still doable.
> > 
> > Before this modification there are two methods have been used to get the
> > clocks connected to an AHCI device: clk_get() - to get the very first
> > clock in the list and of_clk_get() - to get the rest of them. Basically
> > the platforms with non-OF-based clocks definition could specify only a
> > single reference clock source. The platforms with OF-hw clocks have been
> > luckier and could setup up to AHCI_MAX_CLKS clocks. Such semantic can be
> > retained with using devm_clk_bulk_get_all() to retrieve the clocks defined
> > via the DT firmware and devm_clk_get_optional() otherwise. In both cases
> > using the device-managed version of the methods will cause the automatic
> > resources deallocation on the AHCI device removal event. The only
> > complicated part in the suggested approach is the explicit allocation and
> > initialization of the clk_bulk_data structure instance for the non-OF
> > reference clocks. It's required in order to use the Bulk Clocks API for
> > the both denoted cases of the clocks definition.
> > 
> > Note aside with the clock-related code reduction and natural
> > simplification, there are several bonuses the suggested modification
> > provides. First of all the limitation of having no greater than
> > AHCI_MAX_CLKS clocks is now removed, since the devm_clk_bulk_get_all()
> > method will allocate as many reference clocks data descriptors as there
> > are clocks specified for the device. Secondly the clock names are
> > auto-detected. So the glue drivers can make sure that the required clocks
> > are specified just by checking the clock IDs in the clk_bulk_data array.
> > Thirdly using the handy Bulk Clocks kernel API improves the
> > clocks-handling code readability. And the last but not least this
> > modification implements a true optional clocks support to the
> > ahci_platform_get_resources() method. Indeed the previous clocks getting
> > procedure just stopped getting the clocks on any errors (aside from
> > non-critical -EPROBE_DEFER) in a way so the callee wasn't even informed
> > about abnormal loop termination. The new implementation lacks of such
> > problem. The ahci_platform_get_resources() will return an error code if
> > the corresponding clocks getting method ends execution abnormally.
> > 
> > Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> > ---
> >  drivers/ata/ahci.h             |  4 +-
> >  drivers/ata/libahci_platform.c | 82 +++++++++++++++-------------------
> >  2 files changed, 37 insertions(+), 49 deletions(-)
> > 
> > diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
> > index eeac5482f1d1..1564c691094a 100644
> > --- a/drivers/ata/ahci.h
> > +++ b/drivers/ata/ahci.h
> > @@ -38,7 +38,6 @@
> >  
> >  enum {
> >  	AHCI_MAX_PORTS		= 32,
> > -	AHCI_MAX_CLKS		= 5,
> >  	AHCI_MAX_SG		= 168, /* hardware max is 64K */
> >  	AHCI_DMA_BOUNDARY	= 0xffffffff,
> >  	AHCI_MAX_CMDS		= 32,
> > @@ -341,7 +340,8 @@ struct ahci_host_priv {
> >  	u32			em_msg_type;	/* EM message type */
> >  	u32			remapped_nvme;	/* NVMe remapped device count */
> >  	bool			got_runtime_pm; /* Did we do pm_runtime_get? */
> > -	struct clk		*clks[AHCI_MAX_CLKS]; /* Optional */
> > +	unsigned int		n_clks;
> > +	struct clk_bulk_data	*clks;		/* Optional */
> >  	struct reset_control	*rsts;		/* Optional */
> >  	struct regulator	**target_pwrs;	/* Optional */
> >  	struct regulator	*ahci_regulator;/* Optional */
> > diff --git a/drivers/ata/libahci_platform.c b/drivers/ata/libahci_platform.c
> > index 8eabbb5f208c..d805ddc3a024 100644
> > --- a/drivers/ata/libahci_platform.c
> > +++ b/drivers/ata/libahci_platform.c
> > @@ -8,6 +8,7 @@
> >   *   Anton Vorontsov <avorontsov@...mvista.com>
> >   */
> >  
> > +#include <linux/clk-provider.h>
> >  #include <linux/clk.h>
> >  #include <linux/kernel.h>
> >  #include <linux/gfp.h>
> > @@ -97,28 +98,14 @@ EXPORT_SYMBOL_GPL(ahci_platform_disable_phys);
> >   * ahci_platform_enable_clks - Enable platform clocks
> >   * @hpriv: host private area to store config values
> >   *
> > - * This function enables all the clks found in hpriv->clks, starting at
> > - * index 0. If any clk fails to enable it disables all the clks already
> > - * enabled in reverse order, and then returns an error.
> > + * This function enables all the clks found for the AHCI device.
> >   *
> >   * RETURNS:
> >   * 0 on success otherwise a negative error code
> >   */
> >  int ahci_platform_enable_clks(struct ahci_host_priv *hpriv)
> >  {
> > -	int c, rc;
> > -
> > -	for (c = 0; c < AHCI_MAX_CLKS && hpriv->clks[c]; c++) {
> > -		rc = clk_prepare_enable(hpriv->clks[c]);
> > -		if (rc)
> > -			goto disable_unprepare_clk;
> > -	}
> > -	return 0;
> > -
> > -disable_unprepare_clk:
> > -	while (--c >= 0)
> > -		clk_disable_unprepare(hpriv->clks[c]);
> > -	return rc;
> > +	return clk_bulk_prepare_enable(hpriv->n_clks, hpriv->clks);
> >  }
> >  EXPORT_SYMBOL_GPL(ahci_platform_enable_clks);
> >  
> > @@ -126,16 +113,13 @@ EXPORT_SYMBOL_GPL(ahci_platform_enable_clks);
> >   * ahci_platform_disable_clks - Disable platform clocks
> >   * @hpriv: host private area to store config values
> >   *
> > - * This function disables all the clks found in hpriv->clks, in reverse
> > - * order of ahci_platform_enable_clks (starting at the end of the array).
> > + * This function disables all the clocks enabled before
> > + * (bulk-clocks-disable function is supposed to do that in reverse
> > + * from the enabling procedure order).
> >   */
> >  void ahci_platform_disable_clks(struct ahci_host_priv *hpriv)
> >  {
> > -	int c;
> > -
> > -	for (c = AHCI_MAX_CLKS - 1; c >= 0; c--)
> > -		if (hpriv->clks[c])
> > -			clk_disable_unprepare(hpriv->clks[c]);
> > +	clk_bulk_disable_unprepare(hpriv->n_clks, hpriv->clks);
> >  }
> >  EXPORT_SYMBOL_GPL(ahci_platform_disable_clks);
> >  
> > @@ -292,8 +276,6 @@ static void ahci_platform_put_resources(struct device *dev, void *res)
> >  		pm_runtime_disable(dev);
> >  	}
> >  
> > -	for (c = 0; c < AHCI_MAX_CLKS && hpriv->clks[c]; c++)
> > -		clk_put(hpriv->clks[c]);
> >  	/*
> >  	 * The regulators are tied to child node device and not to the
> >  	 * SATA device itself. So we can't use devm for automatically
> > @@ -374,8 +356,8 @@ static int ahci_platform_get_regulator(struct ahci_host_priv *hpriv, u32 port,
> >   * 1) mmio registers (IORESOURCE_MEM 0, mandatory)
> >   * 2) regulator for controlling the targets power (optional)
> >   *    regulator for controlling the AHCI controller (optional)
> > - * 3) 0 - AHCI_MAX_CLKS clocks, as specified in the devs devicetree node,
> > - *    or for non devicetree enabled platforms a single clock
> > + * 3) all clocks specified in the devicetree node, or a single
> > + *    clock for non-OF platforms (optional)
> >   * 4) resets, if flags has AHCI_PLATFORM_GET_RESETS (optional)
> >   * 5) phys (optional)
> >   *
> > @@ -385,11 +367,10 @@ static int ahci_platform_get_regulator(struct ahci_host_priv *hpriv, u32 port,
> >  struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
> >  						   unsigned int flags)
> >  {
> > +	int enabled_ports = 0, rc = 0, child_nodes;
> >  	struct device *dev = &pdev->dev;
> >  	struct ahci_host_priv *hpriv;
> > -	struct clk *clk;
> >  	struct device_node *child;
> > -	int i, enabled_ports = 0, rc = 0, child_nodes;
> >  	u32 mask_port_map = 0;
> >  
> >  	if (!devres_open_group(dev, NULL, GFP_KERNEL))
> > @@ -413,25 +394,32 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
> >  		}
> >  	}
> >  
> > -	for (i = 0; i < AHCI_MAX_CLKS; i++) {
> > -		/*
> > -		 * For now we must use clk_get(dev, NULL) for the first clock,
> > -		 * because some platforms (da850, spear13xx) are not yet
> > -		 * converted to use devicetree for clocks.  For new platforms
> > -		 * this is equivalent to of_clk_get(dev->of_node, 0).
> > -		 */
> > -		if (i == 0)
> > -			clk = clk_get(dev, NULL);
> > -		else
> > -			clk = of_clk_get(dev->of_node, i);
> > -
> > -		if (IS_ERR(clk)) {
> > -			rc = PTR_ERR(clk);
> > -			if (rc == -EPROBE_DEFER)
> > -				goto err_out;
> > -			break;
> > +	/*
> > +	 * Bulk clock get procedure can fail to find any clock due to running
> > +	 * an a non-OF platform or due to the clocks being defined in bypass
> > +	 * from the DT firmware (like da850, spear13xx). In that case we
> > +	 * fallback to getting a single clock source right from the dev clocks
> > +	 * list.
> > +	 */
> > +	rc = devm_clk_bulk_get_all(dev, &hpriv->clks);
> 

> I would move the error check first here to make things more readable:

Agreed. Good note.

> 
> 	rc = devm_clk_bulk_get_all(dev, &hpriv->clks);
> 	if (rc < 0)
> 		goto err_out;
> 
> 	if (rc) {
> 		/* Got clocks in bulk */
> 		hpriv->n_clks = rc;
> 	} else {
> 		/*
> 		 * No clock bulk found: fallback to manually getting
> 		 * the optional clock.
> 		 */
> 		hpriv->clks = devm_kzalloc(dev, sizeof(*hpriv->clks),
> 					   GFP_KERNEL);
> 		...
> 	}
> 
> And it may be cleaner to move this entire code hunk into a helper,
> something like ahci_platform_get_clks() ?

I'd rather keep the code embedded seeing it won't be used anywhere
than here and in order to keep the ahci_platform_get_resources()
function more-or-less coherent.  Otherwise moving just a part of the
function would be a half-measure since the methods like
ahci_platform_get_regs(), ahci_platform_get_regulators(), etc could be
also unpinned.

-Sergey

> 
> > +	if (rc > 0) {
> > +		hpriv->n_clks = rc;
> > +	} else if (!rc) {
> > +		hpriv->clks = devm_kzalloc(dev, sizeof(*hpriv->clks), GFP_KERNEL);
> > +		if (!hpriv->clks) {
> > +			rc = -ENOMEM;
> > +			goto err_out;
> >  		}
> > -		hpriv->clks[i] = clk;
> > +		hpriv->clks->clk = devm_clk_get_optional(dev, NULL);
> > +		if (IS_ERR(hpriv->clks->clk)) {
> > +			rc = PTR_ERR(hpriv->clks->clk);
> > +			goto err_out;
> > +		} else if (hpriv->clks->clk) {
> > +			hpriv->clks->id = __clk_get_name(hpriv->clks->clk);
> > +			hpriv->n_clks = 1;
> > +		}
> > +	} else {
> > +		goto err_out;
> >  	}
> >  
> >  	hpriv->ahci_regulator = devm_regulator_get(dev, "ahci");
> 
> 
> -- 
> Damien Le Moal
> Western Digital Research

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