ahci: add "em_buffer" attribute for AHCI hosts

Add "em_buffer" attribute for SATA AHCI hosts to provide a way for
userland to access AHCI EM (enclosure management) buffer directly if the
host supports EM.

AHCI driver should support SGPIO EM messages. However the SATA/AHCI
specs did not define the SGPIO message format filled in EM buffer.
Different HW vendors may have different definitions. The mainly purpose
of this attribute is to solve this issue by allowing HW vendors to
provide userland drivers and tools for their SGPIO initiators.

Signed-off-by: Harry Zhang <harry.zhang@amd.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

2 files changed, 111 insertions, 3 deletions

diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
index 5edce4447d8..7113c572447 100644
--- a/drivers/ata/ahci.h
+++ b/drivers/ata/ahci.h
@@ -224,9 +224,12 @@ enum {
         EM_MAX_RETRY                    = 5,
 
         /* em_ctl bits */
-        EM_CTL_RST                      = (1 << 9), /* Reset */
-        EM_CTL_TM                       = (1 << 8), /* Transmit Message */
-        EM_CTL_ALHD                     = (1 << 26), /* Activity LED */
+        EM_CTL_RST              = (1 << 9), /* Reset */
+        EM_CTL_TM               = (1 << 8), /* Transmit Message */
+        EM_CTL_MR               = (1 << 0), /* Message Recieved */
+        EM_CTL_ALHD             = (1 << 26), /* Activity LED */
+        EM_CTL_XMT              = (1 << 25), /* Transmit Only */
+        EM_CTL_SMB              = (1 << 24), /* Single Message Buffer */
 
         /* em message type */
         EM_MSG_TYPE_LED         = (1 << 0), /* LED */
@@ -288,6 +291,7 @@ struct ahci_host_priv {
         u32                     saved_cap2;     /* saved initial cap2 */
         u32                     saved_port_map; /* saved initial port_map */
         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 817bcd023cc..1984a6e89e8 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -108,11 +108,18 @@ static ssize_t ahci_show_host_version(struct device *dev,
                                       struct device_attribute *attr, char *buf);
 static ssize_t ahci_show_port_cmd(struct device *dev,
                                   struct device_attribute *attr, char *buf);
+static ssize_t ahci_read_em_buffer(struct device *dev,
+                                   struct device_attribute *attr, char *buf);
+static ssize_t ahci_store_em_buffer(struct device *dev,
+                                    struct device_attribute *attr,
+                                    const char *buf, size_t size);
 
 static DEVICE_ATTR(ahci_host_caps, S_IRUGO, ahci_show_host_caps, NULL);
 static DEVICE_ATTR(ahci_host_cap2, S_IRUGO, ahci_show_host_cap2, NULL);
 static DEVICE_ATTR(ahci_host_version, S_IRUGO, ahci_show_host_version, NULL);
 static DEVICE_ATTR(ahci_port_cmd, S_IRUGO, ahci_show_port_cmd, NULL);
+static DEVICE_ATTR(em_buffer, S_IWUSR | S_IRUGO,
+                   ahci_read_em_buffer, ahci_store_em_buffer);
 
 static struct device_attribute *ahci_shost_attrs[] = {
         &dev_attr_link_power_management_policy,
@@ -122,6 +129,7 @@ static struct device_attribute *ahci_shost_attrs[] = {
         &dev_attr_ahci_host_cap2,
         &dev_attr_ahci_host_version,
         &dev_attr_ahci_port_cmd,
+        &dev_attr_em_buffer,
         NULL
 };
 
@@ -252,6 +260,101 @@ static ssize_t ahci_show_port_cmd(struct device *dev,
         return sprintf(buf, "%x\n", readl(port_mmio + PORT_CMD));
 }
 
+static ssize_t ahci_read_em_buffer(struct device *dev,
+                                   struct device_attribute *attr, char *buf)
+{
+        struct Scsi_Host *shost = class_to_shost(dev);
+        struct ata_port *ap = ata_shost_to_port(shost);
+        struct ahci_host_priv *hpriv = ap->host->private_data;
+        void __iomem *mmio = hpriv->mmio;
+        void __iomem *em_mmio = mmio + hpriv->em_loc;
+        u32 em_ctl, msg;
+        unsigned long flags;
+        size_t count;
+        int i;
+
+        spin_lock_irqsave(ap->lock, flags);
+
+        em_ctl = readl(mmio + HOST_EM_CTL);
+        if (!(ap->flags & ATA_FLAG_EM) || em_ctl & EM_CTL_XMT ||
+            !(hpriv->em_msg_type & EM_MSG_TYPE_SGPIO)) {
+                spin_unlock_irqrestore(ap->lock, flags);
+                return -EINVAL;
+        }
+
+        if (!(em_ctl & EM_CTL_MR)) {
+                spin_unlock_irqrestore(ap->lock, flags);
+                return -EAGAIN;
+        }
+
+        if (!(em_ctl & EM_CTL_SMB))
+                em_mmio += hpriv->em_buf_sz;
+
+        count = hpriv->em_buf_sz;
+
+        /* the count should not be larger than PAGE_SIZE */
+        if (count > PAGE_SIZE) {
+                if (printk_ratelimit())
+                        ata_port_printk(ap, KERN_WARNING,
+                                        "EM read buffer size too large: "
+                                        "buffer size %u, page size %lu\n",
+                                        hpriv->em_buf_sz, PAGE_SIZE);
+                count = PAGE_SIZE;
+        }
+
+        for (i = 0; i < count; i += 4) {
+                msg = readl(em_mmio + i);
+                buf[i] = msg & 0xff;
+                buf[i + 1] = (msg >> 8) & 0xff;
+                buf[i + 2] = (msg >> 16) & 0xff;
+                buf[i + 3] = (msg >> 24) & 0xff;
+        }
+
+        spin_unlock_irqrestore(ap->lock, flags);
+
+        return i;
+}
+
+static ssize_t ahci_store_em_buffer(struct device *dev,
+                                    struct device_attribute *attr,
+                                    const char *buf, size_t size)
+{
+        struct Scsi_Host *shost = class_to_shost(dev);
+        struct ata_port *ap = ata_shost_to_port(shost);
+        struct ahci_host_priv *hpriv = ap->host->private_data;
+        void __iomem *mmio = hpriv->mmio;
+        void __iomem *em_mmio = mmio + hpriv->em_loc;
+        u32 em_ctl, msg;
+        unsigned long flags;
+        int i;
+
+        /* check size validity */
+        if (!(ap->flags & ATA_FLAG_EM) ||
+            !(hpriv->em_msg_type & EM_MSG_TYPE_SGPIO) ||
+            size % 4 || size > hpriv->em_buf_sz)
+                return -EINVAL;
+
+        spin_lock_irqsave(ap->lock, flags);
+
+        em_ctl = readl(mmio + HOST_EM_CTL);
+        if (em_ctl & EM_CTL_TM) {
+                spin_unlock_irqrestore(ap->lock, flags);
+                return -EBUSY;
+        }
+
+        for (i = 0; i < size; i += 4) {
+                msg = buf[i] | buf[i + 1] << 8 |
+                      buf[i + 2] << 16 | buf[i + 3] << 24;
+                writel(msg, em_mmio + i);
+        }
+
+        writel(em_ctl | EM_CTL_TM, mmio + HOST_EM_CTL);
+
+        spin_unlock_irqrestore(ap->lock, flags);
+
+        return size;
+}
+
 /**
  *      ahci_save_initial_config - Save and fixup initial config values
  *      @dev: target AHCI device
@@ -2099,6 +2202,7 @@ void ahci_set_em_messages(struct ahci_host_priv *hpriv,
         if (messages) {
                 /* store em_loc */
                 hpriv->em_loc = ((em_loc >> 16) * 4);
+                hpriv->em_buf_sz = ((em_loc & 0xff) * 4);
                 hpriv->em_msg_type = messages;
                 pi->flags |= ATA_FLAG_EM;
                 if (!(em_ctl & EM_CTL_ALHD))