Re: [PATCH 05/21] ata: libahci_platform: Convert to using devm bulk clocks API

Serge Semin
2022-04-09T05:02:31Z

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@baikalelectronics.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@ru.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