Re: [PATCH 12/21] ata: libahci: Discard redundant force_port_map parameter

[Serge Semin]

On Thu, Mar 24, 2022 at 11:05:58AM +0900, Damien Le Moal wrote:
> On 3/24/22 09:16, Serge Semin wrote:
> > Currently there are four port-map-related fields declared in the
> > ahci_host_priv structure and used to setup the HBA ports mapping. First
> > the ports-mapping is read from the PI register and immediately stored in
> > the saved_port_map field. If forced_port_map is initialized with non-zero
> > value then its value will have greater priority over the value read from
> > PI, thus it will override the saved_port_map field. That value will be then
> > masked by a non-zero mask_port_map field and after some sanity checks it
> > will be stored in the ahci_host_priv.port_map field as a final port
> > mapping.
> > 
> > As you can see the logic is a bit too complicated for such a simple task.
> > We can freely get rid from at least one of the fields with no change to
> > the implemented semantic. The force_port_map field can be replaced with
> > taking non-zero saved_port_map value into account. So if saved_port_map is
> > pre-initialized by the glue-driver/platform-specific code then it will
> 

> glue-driver == LLDD (low level device driver), for the entire series please.

Why? It's a normal term and well known amongst developers. I've used it
in a plenty of my patches before and none of them has been questioned in that
part so far.

-Sergey

> 
> > have greater priority over the value read from PI register and will be
> > used as actual HBA ports mapping later on. Thus the ports map forcing task
> > will be just transferred from the force_port_map to saved_port_map field.
> > 
> > This modification will perfectly fit into the feature of having OF-based
> > initialization of the HW-init HBA CSR fields we are about to introduce in
> > the next commit.
> > 
> > Signed-off-by: Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx>
> > ---
> >  drivers/ata/ahci.c             |  2 +-
> >  drivers/ata/ahci.h             |  1 -
> >  drivers/ata/libahci.c          | 10 ++++++----
> >  drivers/ata/libahci_platform.c |  2 +-
> >  4 files changed, 8 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
> > index ab5811ef5a53..8ce0d166cc8d 100644
> > --- a/drivers/ata/ahci.c
> > +++ b/drivers/ata/ahci.c
> > @@ -654,7 +654,7 @@ static void ahci_pci_save_initial_config(struct pci_dev *pdev,
> >  {
> >  	if (pdev->vendor == PCI_VENDOR_ID_JMICRON && pdev->device == 0x2361) {
> >  		dev_info(&pdev->dev, "JMB361 has only one port\n");
> > -		hpriv->force_port_map = 1;
> > +		hpriv->saved_port_map = 1;
> >  	}
> >  
> >  	/*
> > diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
> > index 04690b4168a3..519d148ecaea 100644
> > --- a/drivers/ata/ahci.h
> > +++ b/drivers/ata/ahci.h
> > @@ -329,7 +329,6 @@ struct ahci_port_priv {
> >  struct ahci_host_priv {
> >  	/* Input fields */
> >  	unsigned int		flags;		/* AHCI_HFLAG_* */
> > -	u32			force_port_map;	/* force port map */
> >  	u32			mask_port_map;	/* mask out particular bits */
> >  
> >  	void __iomem *		mmio;		/* bus-independent mem map */
> > diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
> > index 0ed484e04fd6..011175e82174 100644
> > --- a/drivers/ata/libahci.c
> > +++ b/drivers/ata/libahci.c
> > @@ -453,7 +453,6 @@ void ahci_save_initial_config(struct device *dev, struct ahci_host_priv *hpriv)
> >  	 * reset.  Values without are used for driver operation.
> >  	 */
> >  	hpriv->saved_cap = cap = readl(mmio + HOST_CAP);
> > -	hpriv->saved_port_map = port_map = readl(mmio + HOST_PORTS_IMPL);
> >  
> >  	/* CAP2 register is only defined for AHCI 1.2 and later */
> >  	vers = readl(mmio + HOST_VERSION);
> > @@ -517,10 +516,13 @@ void ahci_save_initial_config(struct device *dev, struct ahci_host_priv *hpriv)
> >  		cap &= ~HOST_CAP_SXS;
> >  	}
> >  
> > -	if (hpriv->force_port_map && port_map != hpriv->force_port_map) {
> > +	/* Override the HBA ports mapping if the platform needs it */
> > +	port_map = readl(mmio + HOST_PORTS_IMPL);
> > +	if (hpriv->saved_port_map && port_map != hpriv->saved_port_map) {
> >  		dev_info(dev, "forcing port_map 0x%x -> 0x%x\n",
> > -			 port_map, hpriv->force_port_map);
> > -		port_map = hpriv->force_port_map;
> > +			 port_map, hpriv->saved_port_map);
> > +		port_map = hpriv->saved_port_map;
> > +	} else {
> >  		hpriv->saved_port_map = port_map;
> >  	}
> >  
> > diff --git a/drivers/ata/libahci_platform.c b/drivers/ata/libahci_platform.c
> > index febad33aa43c..5cbc2c42164d 100644
> > --- a/drivers/ata/libahci_platform.c
> > +++ b/drivers/ata/libahci_platform.c
> > @@ -539,7 +539,7 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
> >  	}
> >  
> >  	of_property_read_u32(dev->of_node,
> > -			     "ports-implemented", &hpriv->force_port_map);
> > +			     "ports-implemented", &hpriv->saved_port_map);
> >  
> >  	if (child_nodes) {
> >  		for_each_child_of_node(dev->of_node, child) {
> 
> 
> -- 
> Damien Le Moal
> Western Digital Research