Date:   Thu, 16 Jun 2022 00:11:34 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>
Cc:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Hans de Goede <hdegoede@...hat.com>,
        Jens Axboe <axboe@...nel.dk>, Hannes Reinecke <hare@...e.de>,
        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 v4 16/23] ata: ahci: Introduce firmware-specific caps
 initialization

On Tue, Jun 14, 2022 at 05:42:35PM +0900, Damien Le Moal wrote:
> On 6/10/22 17:17, Serge Semin wrote:
> > There are systems with no BIOS or comprehensive embedded firmware which
> > could be able to properly initialize the SATA AHCI controller
> > platform-specific capabilities. In that case a good alternative to having
> > a clever bootloader is to create a device tree node with the properties
> > well describing all the AHCI-related platform specifics. All the settings
> > which are normally detected and marked as available in the HBA and its
> > ports capabilities fields [1] could be defined in the platform DTB by
> > means of a set of the dedicated properties. Such approach perfectly fits
> > to the DTB-philosophy - to provide hardware/platform description.
> > 
> > So here we suggest to extend the SATA AHCI device tree bindings with two
> > additional DT-properties:
> > 1) "hba-cap" - HBA platform generic capabilities like:
> >    - SSS - Staggered Spin-up support.
> >    - SMPS - Mechanical Presence Switch support.
> > 2) "hba-port-cap" - HBA platform port capabilities like:
> >    - HPCP - Hot Plug Capable Port.
> >    - MPSP - Mechanical Presence Switch Attached to Port.
> >    - CPD - Cold Presence Detection.
> >    - ESP - External SATA Port.
> >    - FBSCP - FIS-based Switching Capable Port.
> > All of these capabilities require to have a corresponding hardware
> > configuration. Thus it's ok to have them defined in DTB.
> > 
> > Even though the driver currently takes into account the state of the ESP
> > and FBSCP flags state only, there is nothing wrong with having all of them
> > supported by the generic AHCI library in order to have a complete OF-based
> > platform-capabilities initialization procedure. These properties will be
> > parsed in the ahci_platform_get_resources() method and their values will
> > be stored in the saved_* fields of the ahci_host_priv structure, which in
> > its turn then will be used to restore the H.CAP, H.PI and P#.CMD
> > capability fields on device init and after HBA reset.
> > 
> > Please note this modification concerns the HW-init HBA and its ports flags
> > only, which are by specification [1] are supposed to be initialized by the
> > BIOS/platform firmware/expansion ROM and which are normally declared in
> > the one-time-writable-after-reset register fields. Even though these flags
> > aren't supposed to be cleared after HBA reset some AHCI instances may
> > violate that rule so we still need to perform the fields resetting after
> > each reset. Luckily the corresponding functionality has already been
> > partly implemented in the framework of the ahci_save_initial_config() and
> > ahci_restore_initial_config() methods.
> > 
> > [1] Serial ATA AHCI 1.3.1 Specification, p. 103
> > 
> > Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> > 
> > ---
> > 
> > Changelog v4:
> > - Convert the boolean properties to the bitfield DT-properties. (@Rob)
> > ---
> >  drivers/ata/ahci.h             |  1 +
> >  drivers/ata/libahci.c          | 51 ++++++++++++++++++++++++++++------
> >  drivers/ata/libahci_platform.c | 41 +++++++++++++++++++++++++--
> >  3 files changed, 82 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
> > index 8b9826533ae5..0de221055961 100644
> > --- a/drivers/ata/ahci.h
> > +++ b/drivers/ata/ahci.h
> > @@ -337,6 +337,7 @@ struct ahci_host_priv {
> >  	u32			saved_cap;	/* saved initial cap */
> >  	u32			saved_cap2;	/* saved initial cap2 */
> >  	u32			saved_port_map;	/* saved initial port_map */
> > +	u32			saved_port_cap[AHCI_MAX_PORTS]; /* saved port_cap */
> >  	u32 			em_loc; /* enclosure management location */
> >  	u32			em_buf_sz;	/* EM buffer size in byte */
> >  	u32			em_msg_type;	/* EM message type */
> > diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
> > index 1ffaa5f5f21a..954386a2b500 100644
> > --- a/drivers/ata/libahci.c
> > +++ b/drivers/ata/libahci.c
> > @@ -16,6 +16,7 @@
> >   * http://www.intel.com/technology/serialata/pdf/rev1_1.pdf
> >   */
> >  
> > +#include <linux/bitops.h>
> >  #include <linux/kernel.h>
> >  #include <linux/gfp.h>
> >  #include <linux/module.h>
> > @@ -443,16 +444,28 @@ static ssize_t ahci_show_em_supported(struct device *dev,
> >  void ahci_save_initial_config(struct device *dev, struct ahci_host_priv *hpriv)
> >  {
> >  	void __iomem *mmio = hpriv->mmio;
> > -	u32 cap, cap2, vers, port_map;
> > +	void __iomem *port_mmio;
> > +	unsigned long port_map;
> > +	u32 cap, cap2, vers;
> >  	int i;
> >  
> >  	/* make sure AHCI mode is enabled before accessing CAP */
> >  	ahci_enable_ahci(mmio);
> >  
> > -	/* Values prefixed with saved_ are written back to host after
> > -	 * reset.  Values without are used for driver operation.
> > +	/*
> > +	 * Values prefixed with saved_ are written back to the HBA and ports
> > +	 * registers after reset. Values without are used for driver operation.
> > +	 */
> > +
> > +	/*
> > +	 * Override HW-init HBA capability fields with the platform-specific
> > +	 * values. The rest of the HBA capabilities are defined as Read-only
> > +	 * and can't be modified in CSR anyway.
> >  	 */
> > -	hpriv->saved_cap = cap = readl(mmio + HOST_CAP);
> > +	cap = readl(mmio + HOST_CAP);
> > +	if (hpriv->saved_cap)
> > +		cap = (cap & ~(HOST_CAP_SSS | HOST_CAP_MPS)) | hpriv->saved_cap;
> > +	hpriv->saved_cap = cap;
> >  
> >  	/* CAP2 register is only defined for AHCI 1.2 and later */
> >  	vers = readl(mmio + HOST_VERSION);
> > @@ -519,7 +532,7 @@ void ahci_save_initial_config(struct device *dev, struct ahci_host_priv *hpriv)
> >  	/* 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",
> > +		dev_info(dev, "forcing port_map 0x%lx -> 0x%x\n",
> 

> This change is not necessary.

It is. The port_map type has been changed.

> 
> >  			 port_map, hpriv->saved_port_map);
> >  		port_map = hpriv->saved_port_map;
> >  	} else {
> > @@ -527,7 +540,7 @@ void ahci_save_initial_config(struct device *dev, struct ahci_host_priv *hpriv)
> >  	}
> >  
> >  	if (hpriv->mask_port_map) {
> > -		dev_warn(dev, "masking port_map 0x%x -> 0x%x\n",
> > +		dev_warn(dev, "masking port_map 0x%lx -> 0x%lx\n",
> 
> Same.

ditto

> 
> >  			port_map,
> >  			port_map & hpriv->mask_port_map);
> >  		port_map &= hpriv->mask_port_map;
> > @@ -546,7 +559,7 @@ void ahci_save_initial_config(struct device *dev, struct ahci_host_priv *hpriv)
> >  		 */
> >  		if (map_ports > ahci_nr_ports(cap)) {
> >  			dev_warn(dev,
> > -				 "implemented port map (0x%x) contains more ports than nr_ports (%u), using nr_ports\n",
> > +				 "implemented port map (0x%lx) contains more ports than nr_ports (%u), using nr_ports\n",
> 
> Same.

ditto.

> 
> >  				 port_map, ahci_nr_ports(cap));
> >  			port_map = 0;
> >  		}
> > @@ -555,12 +568,26 @@ void ahci_save_initial_config(struct device *dev, struct ahci_host_priv *hpriv)
> >  	/* fabricate port_map from cap.nr_ports for < AHCI 1.3 */
> >  	if (!port_map && vers < 0x10300) {
> >  		port_map = (1 << ahci_nr_ports(cap)) - 1;
> > -		dev_warn(dev, "forcing PORTS_IMPL to 0x%x\n", port_map);
> > +		dev_warn(dev, "forcing PORTS_IMPL to 0x%lx\n", port_map);
> 
> And again not needed.

and ditto.

> 
> >  
> >  		/* write the fixed up value to the PI register */
> >  		hpriv->saved_port_map = port_map;
> >  	}
> >  
> > +	/*
> > +	 * Preserve the ports capabilities defined by the platform. Note there
> > +	 * is no need in storing the rest of the P#.CMD fields since they are
> > +	 * volatile.
> > +	 */
> > +	for_each_set_bit(i, &port_map, AHCI_MAX_PORTS) {
> > +		if (hpriv->saved_port_cap[i])
> > +			continue;
> > +
> > +		port_mmio = __ahci_port_base(hpriv, i);
> > +		hpriv->saved_port_cap[i] =
> > +			readl(port_mmio + PORT_CMD) & PORT_CMD_CAP;
> > +	}
> > +
> >  	/* record values to use during operation */
> >  	hpriv->cap = cap;
> >  	hpriv->cap2 = cap2;
> > @@ -590,13 +617,21 @@ EXPORT_SYMBOL_GPL(ahci_save_initial_config);
> >  static void ahci_restore_initial_config(struct ata_host *host)
> >  {
> >  	struct ahci_host_priv *hpriv = host->private_data;
> > +	unsigned long port_map = hpriv->port_map;
> >  	void __iomem *mmio = hpriv->mmio;
> > +	void __iomem *port_mmio;
> > +	int i;
> >  
> >  	writel(hpriv->saved_cap, mmio + HOST_CAP);
> >  	if (hpriv->saved_cap2)
> >  		writel(hpriv->saved_cap2, mmio + HOST_CAP2);
> >  	writel(hpriv->saved_port_map, mmio + HOST_PORTS_IMPL);
> >  	(void) readl(mmio + HOST_PORTS_IMPL);	/* flush */
> > +
> > +	for_each_set_bit(i, &port_map, AHCI_MAX_PORTS) {
> > +		port_mmio = __ahci_port_base(hpriv, i);
> > +		writel(hpriv->saved_port_cap[i], port_mmio + PORT_CMD);
> > +	}
> >  }
> >  
> >  static unsigned ahci_scr_offset(struct ata_port *ap, unsigned int sc_reg)
> > diff --git a/drivers/ata/libahci_platform.c b/drivers/ata/libahci_platform.c
> > index efe640603f3f..8b542a8bc487 100644
> > --- a/drivers/ata/libahci_platform.c
> > +++ b/drivers/ata/libahci_platform.c
> > @@ -23,6 +23,7 @@
> >  #include <linux/pm_runtime.h>
> >  #include <linux/of_platform.h>
> >  #include <linux/reset.h>
> > +
> 
> white line change.

Ok. I'll drop it.

-Sergey

> 
> >  #include "ahci.h"
> >  
> >  static void ahci_host_stop(struct ata_host *host);
> > @@ -383,6 +384,34 @@ static int ahci_platform_get_regulator(struct ahci_host_priv *hpriv, u32 port,
> >  	return rc;
> >  }
> >  
> > +static int ahci_platform_get_firmware(struct ahci_host_priv *hpriv,
> > +				      struct device *dev)
> > +{
> > +	struct device_node *child;
> > +	u32 port;
> > +
> > +	if (!of_property_read_u32(dev->of_node, "hba-cap", &hpriv->saved_cap))
> > +		hpriv->saved_cap &= (HOST_CAP_SSS | HOST_CAP_MPS);
> > +
> > +	of_property_read_u32(dev->of_node,
> > +			     "ports-implemented", &hpriv->saved_port_map);
> > +
> > +	for_each_child_of_node(dev->of_node, child) {
> > +		if (!of_device_is_available(child))
> > +			continue;
> > +
> > +		if (of_property_read_u32(child, "reg", &port)) {
> > +			of_node_put(child);
> > +			return -EINVAL;
> > +		}
> > +
> > +		if (!of_property_read_u32(child, "hba-port-cap", &hpriv->saved_port_cap[port]))
> > +			hpriv->saved_port_cap[port] &= PORT_CMD_CAP;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> >  /**
> >   * ahci_platform_get_resources - Get platform resources
> >   * @pdev: platform device to get resources for
> > @@ -523,9 +552,6 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
> >  		goto err_out;
> >  	}
> >  
> > -	of_property_read_u32(dev->of_node,
> > -			     "ports-implemented", &hpriv->saved_port_map);
> > -
> >  	if (child_nodes) {
> >  		for_each_child_of_node(dev->of_node, child) {
> >  			u32 port;
> > @@ -590,6 +616,15 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
> >  		if (rc == -EPROBE_DEFER)
> >  			goto err_out;
> >  	}
> > +
> > +	/*
> > +	 * Retrieve firmware-specific flags which then will be used to set
> > +	 * the HW-init fields of HBA and its ports
> > +	 */
> > +	rc = ahci_platform_get_firmware(hpriv, dev);
> > +	if (rc)
> > +		goto err_out;
> > +
> >  	pm_runtime_enable(dev);
> >  	pm_runtime_get_sync(dev);
> >  	hpriv->got_runtime_pm = true;
> 
> 
> -- 
> Damien Le Moal
> Western Digital Research

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