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Subject[PATCH 3.16 032/233] ahci: Acer SA5-271 SSD Not Detected Fix
3.16.48-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Sui Chen <suichen6@gmail.com>

commit 8bfd174312629866efa535193d9e563768ff4307 upstream.

(Correction in this resend: fixed function name acer_sa5_271_workaround; fixed
the always-true condition in the function; fixed description.)

On the Acer Switch Alpha 12 (model number: SA5-271), the internal SSD may not
get detected because the port_map and CAP.nr_ports combination causes the driver
to skip the port that is actually connected to the SSD. More specifically,
either all SATA ports are identified as DUMMY, or all ports get ``link down''
and never get up again.

This problem occurs occasionally. When this problem occurs, CAP may hold a
value of 0xC734FF00 or 0xC734FF01 and port_map may hold a value of 0x00 or 0x01.
When this problem does not occur, CAP holds a value of 0xC734FF02 and port_map
may hold a value of 0x07. Overriding the CAP value to 0xC734FF02 and port_map to
0x7 significantly reduces the occurrence of this problem.

Link: https://bugzilla.kernel.org/attachment.cgi?id=253091
Signed-off-by: Sui Chen <suichen6@gmail.com>
Tested-by: Damian Ivanov <damianatorrpm@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/ata/ahci.c | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)

--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -1313,6 +1313,40 @@ static inline void ahci_gtf_filter_worka
{}
#endif

+/*
+ * On the Acer Aspire Switch Alpha 12, sometimes all SATA ports are detected
+ * as DUMMY, or detected but eventually get a "link down" and never get up
+ * again. When this happens, CAP.NP may hold a value of 0x00 or 0x01, and the
+ * port_map may hold a value of 0x00.
+ *
+ * Overriding CAP.NP to 0x02 and the port_map to 0x7 will reveal all 3 ports
+ * and can significantly reduce the occurrence of the problem.
+ *
+ * https://bugzilla.kernel.org/show_bug.cgi?id=189471
+ */
+static void acer_sa5_271_workaround(struct ahci_host_priv *hpriv,
+ struct pci_dev *pdev)
+{
+ static const struct dmi_system_id sysids[] = {
+ {
+ .ident = "Acer Switch Alpha 12",
+ .matches = {
+ DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
+ DMI_MATCH(DMI_PRODUCT_NAME, "Switch SA5-271")
+ },
+ },
+ { }
+ };
+
+ if (dmi_check_system(sysids)) {
+ dev_info(&pdev->dev, "enabling Acer Switch Alpha 12 workaround\n");
+ if ((hpriv->saved_cap & 0xC734FF00) == 0xC734FF00) {
+ hpriv->port_map = 0x7;
+ hpriv->cap = 0xC734FF02;
+ }
+ }
+}
+
static int ahci_init_interrupts(struct pci_dev *pdev, unsigned int n_ports,
struct ahci_host_priv *hpriv)
{
@@ -1565,6 +1599,10 @@ static int ahci_init_one(struct pci_dev
"online status unreliable, applying workaround\n");
}

+
+ /* Acer SA5-271 workaround modifies private_data */
+ acer_sa5_271_workaround(hpriv, pdev);
+
/* CAP.NP sometimes indicate the index of the last enabled
* port, at other times, that of the last possible port, so
* determining the maximum port number requires looking at
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