linux-kernel - Re: [PATCH v3 08/23] ata: libahci_platform: Add function returning a clock-handle by id

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Date:   Fri, 13 May 2022 11:32:09 +0200
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Serge Semin <fancer.lancer@...il.com>,
        Hannes Reinecke <hare@...e.de>
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 v3 08/23] ata: libahci_platform: Add function returning a
 clock-handle by id

On 2022/05/12 16:26, Serge Semin wrote:
> On Thu, May 12, 2022 at 08:32:37AM +0200, Hannes Reinecke wrote:
>> On 5/12/22 01:17, Serge Semin wrote:
>>> Since all the clocks are retrieved by the method
>>> ahci_platform_get_resources() there is no need for the LLD (glue) drivers
>>> to be looking for some particular of them in the kernel clocks table
>>> again. Instead we suggest to add a simple method returning a
>>> device-specific clock with passed connection ID if it is managed to be
>>> found. Otherwise the function will return NULL. Thus the glue-drivers
>>> won't need to either manually touching the hpriv->clks array or calling
>>> clk_get()-friends. The AHCI platform drivers will be able to use the new
>>> function right after the ahci_platform_get_resources() method invocation
>>> and up to the device removal.
>>>
>>> Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
>>>
>>> ---
>>>
>>> Changelog v2:
>>> - Fix some grammar mistakes in the method description.
>>> ---
>>>   drivers/ata/libahci_platform.c | 27 +++++++++++++++++++++++++++
>>>   include/linux/ahci_platform.h  |  3 +++
>>>   2 files changed, 30 insertions(+)
>>>
>>> diff --git a/drivers/ata/libahci_platform.c b/drivers/ata/libahci_platform.c
>>> index 3cff86c225fd..7ff6626fd569 100644
>>> --- a/drivers/ata/libahci_platform.c
>>> +++ b/drivers/ata/libahci_platform.c
>>> @@ -94,6 +94,33 @@ void ahci_platform_disable_phys(struct ahci_host_priv *hpriv)
>>>   }
>>>   EXPORT_SYMBOL_GPL(ahci_platform_disable_phys);
>>> +/**
>>> + * ahci_platform_find_clk - Find platform clock
>>> + * @hpriv: host private area to store config values
>>> + * @con_id: clock connection ID
>>> + *
>>> + * This function returns a pointer to the clock descriptor of the clock with
>>> + * the passed ID.
>>> + *
>>> + * RETURNS:
>>> + * Pointer to the clock descriptor on success otherwise NULL
>>> + */
>>> +struct clk *ahci_platform_find_clk(struct ahci_host_priv *hpriv, const char *con_id)
>>> +{
>>> +	struct clk *clk = NULL;
>>> +	int i;
>>> +
>>> +	for (i = 0; i < hpriv->n_clks; i++) {
>>> +		if (!strcmp(hpriv->clks[i].id, con_id)) {
>>> +			clk = hpriv->clks[i].clk;
>>> +			break;
>>> +		}
>>> +	}
>>> +
>>> +	return clk;
>>> +}
>>> +EXPORT_SYMBOL_GPL(ahci_platform_find_clk);
>>> +
>>>   /**
>>>    * ahci_platform_enable_clks - Enable platform clocks
>>>    * @hpriv: host private area to store config values
>>> diff --git a/include/linux/ahci_platform.h b/include/linux/ahci_platform.h
>>> index 49e5383d4222..fd964e6a68d6 100644
>>> --- a/include/linux/ahci_platform.h
>>> +++ b/include/linux/ahci_platform.h
>>> @@ -13,6 +13,7 @@
>>>   #include <linux/compiler.h>
>>> +struct clk;
>>>   struct device;
>>>   struct ata_port_info;
>>>   struct ahci_host_priv;
>>> @@ -21,6 +22,8 @@ struct scsi_host_template;
>>>   int ahci_platform_enable_phys(struct ahci_host_priv *hpriv);
>>>   void ahci_platform_disable_phys(struct ahci_host_priv *hpriv);
>>> +struct clk *
>>> +ahci_platform_find_clk(struct ahci_host_priv *hpriv, const char *con_id);
>>>   int ahci_platform_enable_clks(struct ahci_host_priv *hpriv);
>>>   void ahci_platform_disable_clks(struct ahci_host_priv *hpriv);
>>>   int ahci_platform_enable_regulators(struct ahci_host_priv *hpriv);
>>
> 
>> Where is this function being used?
> 
> It will be used in the DWC AHCI SATA driver and can be utilized in the
> rest of the drivers to simplify the available clocks access.
> BTW Damien asked the same question in v1. My response was the same.

Please squash this patch together with the patch introducing the first use of
this function.

> 
> -Sergey
> 
>>
>> Cheers,
>>
>> Hannes
>> -- 
>> Dr. Hannes Reinecke		           Kernel Storage Architect
>> hare@...e.de			                  +49 911 74053 688
>> SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
>> HRB 36809 (AG Nürnberg), GF: Felix Imendörffer


-- 
Damien Le Moal
Western Digital Research