Subject: Re: [PATCH 3/5] irqchip/irq-mvebu-icu: Move the double SATA ports interrupt hack

From: Miquel Raynal <[email-masked]>
Date: Mon, 25 Feb 2019 16:22:37 +0100

Hi Marc,

Marc Zyngier <[email-masked]> wrote on Sat, 23 Feb 2019 19:19:27
+0000:

> On Fri, 22 Feb 2019 14:53:54 +0000,
> Miquel Raynal <[email-masked]> wrote:
> > 
> > When writing the driver, a hack was introduced to configure both SATA
> > interrupts regardless of the port in use to overcome a limitation in
> > the SATA core. Now that this limitation has been addressed, let's
> > clean this driver section and move the hack into the (historically)
> > responsible SATA driver: ahci_platform.
> > 
> > Signed-off-by: Miquel Raynal <[email-masked]>
> > ---
> >  drivers/ata/ahci_platform.c     | 174 ++++++++++++++++++++++++++++++++
> >  drivers/irqchip/irq-mvebu-icu.c |  18 ----
> >  2 files changed, 174 insertions(+), 18 deletions(-)
> > 
> > diff --git a/drivers/ata/ahci_platform.c b/drivers/ata/ahci_platform.c
> > index cf1e0e18a7a9..4401a137e6d5 100644
> > --- a/drivers/ata/ahci_platform.c
> > +++ b/drivers/ata/ahci_platform.c
> > @@ -17,6 +17,7 @@
> >  #include <linux/pm.h>
> >  #include <linux/device.h>
> >  #include <linux/of_device.h>
> > +#include <linux/of_irq.h>
> >  #include <linux/platform_device.h>
> >  #include <linux/libata.h>
> >  #include <linux/ahci_platform.h>
> > @@ -26,6 +27,9 @@
> >  
> >  #define DRV_NAME "ahci"
> >  
> > +#define ICU_SATA0_ICU_ID 109
> > +#define ICU_SATA1_ICU_ID 107
> > +
> >  static const struct ata_port_info ahci_port_info = {
> >  	.flags		= AHCI_FLAG_COMMON,
> >  	.pio_mask	= ATA_PIO4,
> > @@ -44,6 +48,170 @@ static struct scsi_host_template ahci_platform_sht = {
> >  	AHCI_SHT(DRV_NAME),
> >  };
> >  
> > +/*
> > + * The Armada CP110 SATA unit (on A7k/A8k SoCs) has 2 ports, and a dedicated ICU
> > + * entry per port. In the past, the AHCI SATA driver only supported one
> > + * interrupt per SATA unit. To solve this, the 2 SATA wired interrupts in the
> > + * South-Bridge got configured as 1 GIC interrupt in the North-Bridge,
> > + * regardless of the number of SATA ports actually enabled/in use.
> > + *
> > + * Since then, this limitation has been addressed and the hack described
> > + * above has been removed from the ICU driver. However, for compatibility
> > + * it is needed to support DT with just one interrupt and no SATA ports.
> > + * Instead of hacking everywhere in the ahci/libahci code, this quirk has been
> > + * written to manually create the SATA port sub-nodes if they are missing,
> > + * assign them the right port numbers through the "reg" properties and their
> > + * respective "interrupts".  
> 
> I don't think this write-up, however interesting, is useful here. That's the
> kind of war story that makes perfect sense in a commit log, and not much in
> the actual code. I'd suggest you keep the story short and only explain the
> problem the workaround tries to paper over.
> 

Sure.

> > + */
> > +static int ahci_armada_8k_quirk(struct device *dev)
> > +{
> > +	struct device_node *dn = dev->of_node;
> > +	struct property *interrupt = of_find_property(dn, "interrupts", NULL);  
> 
> It'd make more sense if you checked the interrupt property once you actually
> need it.

Ok.

> 
> > +	struct device_node *ports;
> > +	struct property *regs, *ints;
> > +	int rc, i;
> > +
> > +	if (!(of_device_is_compatible(dn, "marvell,armada-8k-ahci") &&  
> 
> Where is this compat string documented?

This string already exists, but you are right that it should have been
documented in Documentation/devicetree/bindings/ata/ahci-platform.txt.
I will write a patch for that.

> 
> > +	      !of_get_child_count(dn)))
> > +		return 0;
> > +
> > +	if (!of_node_get(dn))
> > +		return -EINVAL;  
> 
> Shouldn't you do that first, before having started to mess with the node?

Ok.

> 
> > +
> > +	/* Verify the main SATA node "interrupts" property validity */
> > +	if (!interrupt) {
> > +		rc = -EINVAL;
> > +		goto put_dn;
> > +	}
> > +
> > +	/* Create the two sub-nodes */
> > +	ports = kzalloc(2 * sizeof(*ports), GFP_KERNEL);
> > +	if (!ports) {
> > +		rc = -ENOMEM;
> > +		goto put_dn;
> > +	}
> > +
> > +	for (i = 0; i < 2; i++) {
> > +		of_node_set_flag(&ports[i], OF_DYNAMIC);  
> 
> Do you really expect all users to now have to select OF_DYNAMIC to be able
> to use their system? I'm not sure that's the right thing to do.

I overlooked that point.

However, I just ran a "make ARCH=arm64 defconfig" and it enables
OF_DYNAMIC, so shall we still consider it as a problem?

Would a "select OF_DYNAMIC if ARM64" under "config MVEBU_AHCI" be
appropriate?

> I'd rather see this workaround be handled at probe time, generating the
> right data structures right away, rather than patching the DT from inside
> the kernel to eventually generate these structures. Also, how does this work
> for non-DT?

My first intention was to allocate a second interrupt at probe time,
but this would have not worked because there is a lot of core code
relying on the number of SATA ports (it has an impact on how the core
deals with interrupts).

Doing what you propose is IMHO too hackish and invasive, it would
impact a lot of core code out of the ahci-platform driver because it is
there that the DT is parsed and the structures are allocated.

Also for non-DT situation, I wonder if that is even possible due to the
fact that most of the libahci_platform code relies on of_ functions,
of_ structures, the number of child nodes, etc.

> 
> > +		of_node_init(&ports[i]);
> > +		ports[i].parent = dn;
> > +	}
> > +
> > +	ports[0].full_name = kstrdup("sata-port@0", GFP_KERNEL);
> > +	ports[1].full_name = kstrdup("sata-port@1", GFP_KERNEL);
> > +	if (!ports[0].full_name || !ports[1].full_name) {
> > +		rc = -ENOMEM;
> > +		goto free_ports_names;
> > +	}
> > +
> > +	/* Create the two "reg" and "interrupts" property for the sub-nodes */
> > +	regs = kzalloc(2 * sizeof(*regs), GFP_KERNEL);
> > +	ints = kzalloc(2 * sizeof(*ints), GFP_KERNEL);
> > +	if (!regs || !ints) {
> > +		rc = -ENOMEM;
> > +		goto free_props;
> > +	}
> > +
> > +	for (i = 0; i < 2; i++) {
> > +		regs[i].name = kstrdup("reg", GFP_KERNEL);
> > +		regs[i].length = sizeof(u32);
> > +		regs[i].value = kmalloc(sizeof(regs[i].length), GFP_KERNEL);
> > +
> > +		ints[i].name = kstrdup("interrupts", GFP_KERNEL);
> > +		ints[i].length = interrupt->length;
> > +		ints[i].value = kmemdup(interrupt->value, interrupt->length,
> > +					GFP_KERNEL);
> > +
> > +		if (!regs[i].name || !regs[i].value ||
> > +		    !ints[i].name || !ints[i].value) {
> > +			rc = -ENOMEM;
> > +			goto free_props_allocs;
> > +		}
> > +	}
> > +
> > +	/* Force the values of the ICU interrupts for both ports.  
> 
> Comment formatting.

Missed that, sorry.

> 
> > +	 * In the past, "interrupts" properties had three values:
> > +	 * 1/ ICU interrupt type, 2/ interrupt ID, 3/ interrupt type  
> 
> I don't understand this comment. From what I can see in the last patch, the
> interrupts property always had 2 cells.

Yes, but the bindings for ICU interrupts have changed in a near past
from 3 to 2 cells, we removed the ICU_NSR entry because now there is a
"parent" (GICP, SEI, REI) which will help knowing the interrupt
"type".

It is backward-backward-compatiblity :-/

> 
> > +	 * Now there are only two:
> > +	 * 1/ interrupt ID, 2/ interrupt type
> > +	 * In both case we want to access the penultimate.
> > +	 */
> > +	for (i = 0; i < 2; i++) {
> > +		u32 *reg, *icu_int;
> > +		u8 *value;
> > +
> > +		reg = regs[i].value;
> > +		*reg = cpu_to_be32(i);
> > +
> > +		value = ints[i].value;
> > +		value = &value[ints[i].length - (2 * sizeof(u32))];
> > +		icu_int = (u32 *)value;
> > +		if (!i)
> > +			*icu_int = cpu_to_be32(ICU_SATA0_ICU_ID);
> > +		else
> > +			*icu_int = cpu_to_be32(ICU_SATA1_ICU_ID);
> > +	}
> > +
> > +	for (i = 0; i < 2; i++) {
> > +		ports[i].properties = &regs[i];
> > +		regs[i].next = &ints[i];
> > +		ints[i].next = NULL;
> > +	}
> > +
> > +	/* Create the two sub-nodes by attaching them */
> > +	rc = of_attach_node(&ports[0]);
> > +	if (rc) {
> > +		dev_err(dev, "Compat: cannot attach port0 (err %d)\n", rc);
> > +		goto free_props_allocs;
> > +	}
> > +
> > +	rc = of_attach_node(&ports[1]);
> > +	if (rc) {
> > +		dev_err(dev, "Compat: cannot attach port1 (err %d)\n", rc);
> > +		goto detach_port0;
> > +	}
> > +
> > +	/* Delete the "interrupts" property from the SATA host node */
> > +	rc = of_remove_property(dn, interrupt);
> > +	if (rc) {
> > +		dev_err(dev, "Compat: cannot delete SATA host interrupt\n");
> > +		goto detach_ports;
> > +	}
> > +
> > +	of_node_put(dn);
> > +
> > +	return 0;
> > +
> > +detach_ports:
> > +	of_detach_node(&ports[1]);
> > +
> > +detach_port0:
> > +	of_detach_node(&ports[0]);
> > +
> > +free_props_allocs:
> > +	for (i = 0; i < 2; i++) {
> > +		kfree(regs[i].name);
> > +		kfree(regs[i].value);
> > +		kfree(ints[i].name);
> > +		kfree(ints[i].value);
> > +	}
> > +
> > +free_props:
> > +	kfree(regs);
> > +	kfree(ints);
> > +
> > +free_ports_names:
> > +	for (i = 0; i < 2; i++)
> > +		kfree(ports[i].full_name);
> > +
> > +	kfree(ports);  
> 
> How about using devm allocations instead, since you're going to fail the
> probe anyway?

Yes, will be cleaner.

> 
> > +
> > +put_dn:
> > +	of_node_put(dn);
> > +
> > +	return rc;
> > +	}
> > +
> >  static int ahci_probe(struct platform_device *pdev)
> >  {
> >  	struct device *dev = &pdev->dev;
> > @@ -51,6 +219,12 @@ static int ahci_probe(struct platform_device *pdev)
> >  	const struct ata_port_info *port;
> >  	int rc;
> >  
> > +	rc = ahci_armada_8k_quirk(dev);
> > +	if (rc) {
> > +		dev_err(dev, "Problem with CP110 backward compatibility\n");
> > +		return rc;
> > +	}
> > +
> >  	hpriv = ahci_platform_get_resources(pdev,
> >  					    AHCI_PLATFORM_GET_RESETS);
> >  	if (IS_ERR(hpriv))
> > diff --git a/drivers/irqchip/irq-mvebu-icu.c b/drivers/irqchip/irq-mvebu-icu.c
> > index 547045d89c4b..f3b43f63fe2e 100644
> > --- a/drivers/irqchip/irq-mvebu-icu.c
> > +++ b/drivers/irqchip/irq-mvebu-icu.c
> > @@ -38,8 +38,6 @@
> >  
> >  /* ICU definitions */
> >  #define ICU_MAX_IRQS		207
> > -#define ICU_SATA0_ICU_ID	109
> > -#define ICU_SATA1_ICU_ID	107
> >  
> >  struct mvebu_icu_subset_data {
> >  	unsigned int icu_group;
> > @@ -111,22 +109,6 @@ static void mvebu_icu_write_msg(struct msi_desc *desc, struct msi_msg *msg)
> >  	}
> >  
> >  	writel_relaxed(icu_int, icu->base + ICU_INT_CFG(d->hwirq));
> > -
> > -	/*
> > -	 * The SATA unit has 2 ports, and a dedicated ICU entry per
> > -	 * port. The ahci sata driver supports only one irq interrupt
> > -	 * per SATA unit. To solve this conflict, we configure the 2
> > -	 * SATA wired interrupts in the south bridge into 1 GIC
> > -	 * interrupt in the north bridge. Even if only a single port
> > -	 * is enabled, if sata node is enabled, both interrupts are
> > -	 * configured (regardless of which port is actually in use).
> > -	 */
> > -	if (d->hwirq == ICU_SATA0_ICU_ID || d->hwirq == ICU_SATA1_ICU_ID) {
> > -		writel_relaxed(icu_int,
> > -			       icu->base + ICU_INT_CFG(ICU_SATA0_ICU_ID));
> > -		writel_relaxed(icu_int,
> > -			       icu->base + ICU_INT_CFG(ICU_SATA1_ICU_ID));
> > -	}
> >  }
> >  
> >  static struct irq_chip mvebu_icu_nsr_chip = {  
> 
> Clearly, this is not much of an irqchip patch. I'd expect you either extract
> the irqchip bit in a separate patch.

I am not sure this is valid as it would break bisectability. I have not
tested if it actually fails though (will do and split the patch
depending on the outcome).

> 
> Overall, I'm not sure this patch can fly as is. The dependency on OF_DYNAMIC
> is not exactly great, and the whole thing is likely to fail anyway, as you
> don't even bother selecting that new dependency. I strongly suggest you
> implement the quirk by generating the right structures at the right time.
> 
> Thanks,
> 
> 	M.
> 

Thanks,
Miquèl

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