tty: pl011: fix initialization order of QDF2400 E44

The work-around for Qualcomm Technologies QDF2400 Erratum 44 hinges on a
global variable defined in the pl011 driver.  The ACPI SPCR parsing code
determines whether the work-around is needed, and if so, it changes the
console name from "pl011" to "qdf2400_e44".  The expectation is that
the pl011 driver will implement the work-around when it sees the console
name.  The global variable qdf2400_e44_present is set when that happens.

The problem is that work-around needs to be enabled when the pl011
driver probes, not when the console name is queried.  However, sbsa_probe()
is called before pl011_console_match().  The work-around appeared to work
previously because the default console on QDF2400 platforms was always
ttyAMA1.  The first time sbsa_probe() is called (for ttyAMA0),
qdf2400_e44_present is still false.  Then pl011_console_match() is called,
and it sets qdf2400_e44_present to true.  All subsequent calls to
sbsa_probe() enable the work-around.

The solution is to move the global variable into spcr.c and let the
pl011 driver query it during probe time.  This works because all QDF2400
platforms require SPCR, so parse_spcr() will always be called.
pl011_console_match still checks for the "qdf2400_e44" console name,
but it doesn't do anything else special.

BugLink: https://launchpad.net/bugs/1709123
Fixes: 5a0722b898f8 ("tty: pl011: use "qdf2400_e44" as the earlycon name for QDF2400 E44")
Tested-by: Jeffrey Hugo <jhugo@codeaurora.org>
Signed-off-by: Timur Tabi <timur@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(backported from commit 37ef38f3f83891a2f413fb872bae7d0f9bb95b27)
Signed-off-by: Manoj Iyer <manoj.iyer@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
index 2051a8ce9c853ff90592bc5e496ef85272ceaba1..4c4099f075c9739d997109ebe8e7f14d2399e5a9 100644 (file)
--- a/drivers/acpi/spcr.c
+++ b/drivers/acpi/spcr.c
@@ -16,6 +16,16 @@
 #include <linux/kernel.h>
 #include <linux/serial_core.h>
 
+/*
+ * Erratum 44 for QDF2432v1 and QDF2400v1 SoCs describes the BUSY bit as
+ * occasionally getting stuck as 1. To avoid the potential for a hang, check
+ * TXFE == 0 instead of BUSY == 1. This may not be suitable for all UART
+ * implementations, so only do so if an affected platform is detected in
+ * parse_spcr().
+ */
+bool qdf2400_e44_present;
+EXPORT_SYMBOL(qdf2400_e44_present);
+
 /*
  * Some Qualcomm Datacenter Technologies SoCs have a defective UART BUSY bit.
  * Detect them by examining the OEM fields in the SPCR header, similiar to PCI
@@ -113,8 +123,29 @@ int __init parse_spcr(bool earlycon)
                goto done;
        }
 
-       if (qdf2400_erratum_44_present(&table->header))
-               uart = "qdf2400_e44";
+       /*
+        * If the E44 erratum is required, then we need to tell the pl011
+        * driver to implement the work-around.
+        *
+        * The global variable is used by the probe function when it
+        * creates the UARTs, whether or not they're used as a console.
+        *
+        * If the user specifies "traditional" earlycon, the qdf2400_e44
+        * console name matches the EARLYCON_DECLARE() statement, and
+        * SPCR is not used.  Parameter "earlycon" is false.
+        *
+        * If the user specifies "SPCR" earlycon, then we need to update
+        * the console name so that it also says "qdf2400_e44".  Parameter
+        * "earlycon" is true.
+        *
+        * For consistency, if we change the console name, then we do it
+        * for everyone, not just earlycon.
+        */
+       if (qdf2400_erratum_44_present(&table->header)) {
+               qdf2400_e44_present = true;
+               if (earlycon)
+                       uart = "qdf2400_e44";
+       }
 
        snprintf(opts, sizeof(opts), "%s,%s,0x%llx,%d", uart, iotype,
                 table->serial_port.address, baud_rate);

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 0875f7d01fa55308430dafb6751545f72acbd899..a0eeea48a48a0c10e55a85b9f1375aaf218d1143 100644 (file)
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -142,15 +142,7 @@ static struct vendor_data vendor_sbsa = {
        .fixed_options          = true,
 };
 
-/*
- * Erratum 44 for QDF2432v1 and QDF2400v1 SoCs describes the BUSY bit as
- * occasionally getting stuck as 1. To avoid the potential for a hang, check
- * TXFE == 0 instead of BUSY == 1. This may not be suitable for all UART
- * implementations, so only do so if an affected platform is detected in
- * parse_spcr().
- */
-static bool qdf2400_e44_present = false;
-
+#ifdef CONFIG_ACPI_SPCR_TABLE
 static struct vendor_data vendor_qdt_qdf2400_e44 = {
        .reg_offset             = pl011_std_offsets,
        .fr_busy                = UART011_FR_TXFE,
@@ -165,6 +157,7 @@ static struct vendor_data vendor_qdt_qdf2400_e44 = {
        .always_enabled         = true,
        .fixed_options          = true,
 };
+#endif
 
 static u16 pl011_st_offsets[REG_ARRAY_SIZE] = {
        [REG_DR] = UART01x_DR,
@@ -2370,12 +2363,14 @@ static int __init pl011_console_match(struct console *co, char *name, int idx,
        resource_size_t addr;
        int i;
 
-       if (strcmp(name, "qdf2400_e44") == 0) {
-               pr_info_once("UART: Working around QDF2400 SoC erratum 44");
-               qdf2400_e44_present = true;
-       } else if (strcmp(name, "pl011") != 0) {
+       /*
+        * Systems affected by the Qualcomm Technologies QDF2400 E44 erratum
+        * have a distinct console name, so make sure we check for that.
+        * The actual implementation of the erratum occurs in the probe
+        * function.
+        */
+       if ((strcmp(name, "qdf2400_e44") != 0) && (strcmp(name, "pl011") != 0))
                return -ENODEV;
-       }
 
        if (uart_parse_earlycon(options, &iotype, &addr, &options))
                return -ENODEV;
@@ -2729,11 +2724,17 @@ static int sbsa_uart_probe(struct platform_device *pdev)
        }
        uap->port.irq   = ret;
 
-       uap->reg_offset = vendor_sbsa.reg_offset;
-       uap->vendor     = qdf2400_e44_present ?
-                                       &vendor_qdt_qdf2400_e44 : &vendor_sbsa;
+#ifdef CONFIG_ACPI_SPCR_TABLE
+       if (qdf2400_e44_present) {
+               dev_info(&pdev->dev, "working around QDF2400 SoC erratum 44\n");
+               uap->vendor = &vendor_qdt_qdf2400_e44;
+       } else
+#endif
+               uap->vendor = &vendor_sbsa;
+
+       uap->reg_offset = uap->vendor->reg_offset;
        uap->fifosize   = 32;
-       uap->port.iotype = vendor_sbsa.access_32b ? UPIO_MEM32 : UPIO_MEM;
+       uap->port.iotype = uap->vendor->access_32b ? UPIO_MEM32 : UPIO_MEM;
        uap->port.ops   = &sbsa_uart_pops;
        uap->fixed_baud = baudrate;
 

diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 120f333684ebe316a7fa9c7970db3ba6ba3971c2..7479785176014eb168f35a9732e604a53d149182 100644 (file)
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1155,6 +1155,7 @@ static inline bool acpi_has_watchdog(void) { return false; }
 #endif
 
 #ifdef CONFIG_ACPI_SPCR_TABLE
+extern bool qdf2400_e44_present;
 int parse_spcr(bool earlycon);
 #else
 static inline int parse_spcr(bool earlycon) { return 0; }