Message-ID: <8682b057-fc62-4491-90f9-204736fb88b4@solid-run.com>
Date: Wed, 27 Nov 2024 11:52:10 +0000
From: Josua Mayer <josua@...id-run.com>
To: Damien Le Moal <dlemoal@...nel.org>, Niklas Cassel <cassel@...nel.org>,
	Hans de Goede <hdegoede@...hat.com>
CC: Jon Nettleton <jon@...id-run.com>, Mikhail Anikin
	<mikhail.anikin@...id-run.com>, Yazan Shhady <yazan.shhady@...id-run.com>,
	Rabeeh Khoury <rabeeh@...id-run.com>, "linux-ide@...r.kernel.org"
	<linux-ide@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] ata: libahci_platform: support non-consecutive port
 numbers

Am 25.11.24 um 02:12 schrieb Damien Le Moal:

> On 11/22/24 12:05 AM, Josua Mayer wrote:
>> So far ahci_platform relied on number of child nodes in firmware to
>> allocate arrays and expected port numbers to start from 0 without holes.
>> This number of ports is then set in private structure for use when
>> configuring phys and regulators.
>>
>> Some platforms may not use every port of an ahci controller.
>> E.g. SolidRUN CN9130 Clearfog uses only port 1 but not port 0, leading
>> to the following errors during boot:
>> [    1.719476] ahci f2540000.sata: invalid port number 1
>> [    1.724562] ahci f2540000.sata: No port enabled
>>
>> Remove from ahci_host_priv the property nports which only makes sense
>> when enabled ports are consecutive. It is replaced with AHCI_MAX_PORTS
>> and checks for hpriv->mask_port_map, which indicates each port that is
>> enabled.
>>
>> Update ahci_host_priv properties target_pwrs and phys from dynamically
>> allocated arrays to statically allocated to size AHCI_MAX_PORTS.
>>
>> Update ahci_platform_get_resources to ignore holes in the port numbers
>> and enable ports defined in firmware by their reg property only.
>>
>> When firmware does not define children it is assumed that there is
>> exactly one port, using index 0.
>>
>> I marked this RFC because it was only tested with Linux v6.1, Marvell
>> fork, CN9130 Clearfog Pro which has only port number 1 in device-tree.
>> Further I am not completely sure if it has severe side-effects on
>> other platforms.
>> I plan to submit it again after testing on v6.13-rc1, but do welcome
>> feedback in the meantime, particularly whether this idea of supporting
>> non-consecutive ports is acceptable.
>>
>> Signed-off-by: Josua Mayer <josua@...id-run.com>
> [...]
>
>
>> @@ -539,41 +544,7 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
>>  		hpriv->f_rsts = flags & AHCI_PLATFORM_RST_TRIGGER;
>>  	}
>>  
>> -	/*
>> -	 * Too many sub-nodes most likely means having something wrong with
>> -	 * the firmware.
>> -	 */
>>  	child_nodes = of_get_child_count(dev->of_node);
>> -	if (child_nodes > AHCI_MAX_PORTS) {
>> -		rc = -EINVAL;
>> -		goto err_out;
>> -	}
> Why remove this check ? Your platform may not need ti, but it is still valid
> for others.
The check is superfluous, since the following loop will print a warning
and ignore any child with port number greater than AHCI_MAX_PORTS.
The check merely protected against dynamically allocating greater than
AHCI_MAX_PORTS.
>
>> -
>> -	/*
>> -	 * If no sub-node was found, we still need to set nports to
>> -	 * one in order to be able to use the
>> -	 * ahci_platform_[en|dis]able_[phys|regulators] functions.
>> -	 */
>> -	if (child_nodes)
>> -		hpriv->nports = child_nodes;
>> -	else
>> -		hpriv->nports = 1;
> Same here.
This is already handled in else case of if (child_nodes)
>
>> -
>> -	hpriv->phys = devm_kcalloc(dev, hpriv->nports, sizeof(*hpriv->phys), GFP_KERNEL);
>> -	if (!hpriv->phys) {
>> -		rc = -ENOMEM;
>> -		goto err_out;
>> -	}
>> -	/*
>> -	 * We cannot use devm_ here, since ahci_platform_put_resources() uses
>> -	 * target_pwrs after devm_ have freed memory
>> -	 */
>> -	hpriv->target_pwrs = kcalloc(hpriv->nports, sizeof(*hpriv->target_pwrs), GFP_KERNEL);
>> -	if (!hpriv->target_pwrs) {
>> -		rc = -ENOMEM;
>> -		goto err_out;
>> -	}
> And for platforms that actually have a valid nports with no ID holes, the above
> is OK and uses less memory...
The port number is being used as index into the target_pwrs and phys arrays,
which is why those arrays must allocate at least to the highest port id.
A better way to save memory is by cleaning out this semantic,
e.g. by dynamically allocating a structure of id, phy and supply for each port.
>
> Why not simply adding code that checks the ID of the child nodes ? If there are
> no ID holes, then nothing need to change. If there are holes, then
> hpriv->nports can be set to the highest ID + 1 and you can set
> hpriv->mask_port_map as you go.
This would make the already complex function more complex and less readable.
I prefer to reduce corner cases rather than adding extras.
> With just that, you should get everything
> working with far less changes than you have here.
>
>>  	if (child_nodes) {
>>  		for_each_child_of_node_scoped(dev->of_node, child) {
>>  			u32 port;
>> @@ -587,7 +558,7 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
>>  				goto err_out;
>>  			}
>>  
>> -			if (port >= hpriv->nports) {
>> +			if (port >= AHCI_MAX_PORTS) {
>>  				dev_warn(dev, "invalid port number %d\n", port);
>>  				continue;
>>  			}
>> @@ -625,6 +596,8 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
>>  		 * If no sub-node was found, keep this for device tree
>>  		 * compatibility
>>  		 */
>> +		hpriv->mask_port_map |= BIT(0);
>> +
>>  		rc = ahci_platform_get_phy(hpriv, 0, dev, dev->of_node);
>>  		if (rc)
>>  			goto err_out;
>>
>> ---
>> base-commit: adc218676eef25575469234709c2d87185ca223a
>> change-id: 20241121-ahci-nonconsecutive-ports-a8911b3255a7
>>
>> Best regards,
>

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