Christopher Covington wrote:
The Qualcomm Datacenter Technologies QDF2400 family of SoCs contains a
custom (non-PrimeCell) implementation of the SBSA UART. Occasionally the
BUSY bit in the Flag Register gets stuck as 1, erratum 44 for both 2432v1
and 2400v1 SoCs. Checking that the Transmit FIFO Empty (TXFE) bit is 0,
instead of checking that the BUSY bit is 1, works around the issue. To
facilitate this substitution when UART AMBA Port (UAP) data is available,
introduce vendor-specific inversion of Feature Register bits. For the
earlycon case, implement alternative putc and early_write functions.
Similar to what how ARMv8 ACPI PCI quirks are detected during MCFG parsing,
check the OEM fields of the Serial Port Console Redirection (SPCR) ACPI
table to determine if the current platform is known to be affected by the
erratum.
Please break this up into paragraphs.
+ if (!memcmp(table->header.oem_id, "QCOM ", ACPI_OEM_ID_SIZE))
+ if (!memcmp(table->header.oem_table_id, "QDF2432 ",
+ ACPI_OEM_TABLE_ID_SIZE) ||
+ (!memcmp(table->header.oem_table_id,
+ "QDF2400 ", ACPI_OEM_TABLE_ID_SIZE) &&
+ table->header.oem_revision == 0))
+ uart = "qdf2400_e44";
+
Hey, you just wrote this
And it looks crazy
But here's my function
So call it, maybe?
static bool needs_qdf2400_e44(struct acpi_table_header *h)
{
const char *id;
/* The erratum only applies to Qualcomm Technologies SOCs */
if (memcmp(h->oem_id, "QCOM ", ACPI_OEM_ID_SIZE))
return False;
id = h->oem_table_id;
if (!memcmp(id, "QDF2432 ", ACPI_OEM_TABLE_ID_SIZE))
return True;
if (!memcmp(id, "QDF2000 ", ACPI_OEM_TABLE_ID_SIZE) &&
h->oem_revision == 0)
return True;
return False;
}
...
if (needs_qdf2400_e44(&table->header))
uart = "qdf2400_e44";
+/*
+ * 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 = false;
Please rename this to needs_qdf2400_e44
static u16 pl011_st_offsets[REG_ARRAY_SIZE] = {
[REG_DR] = UART01x_DR,
[REG_ST_DMAWM] = ST_UART011_DMAWM,
@@ -1518,7 +1543,8 @@ static unsigned int pl011_tx_empty(struct uart_port *port)
{
struct uart_amba_port *uap =
container_of(port, struct uart_amba_port, port);
- unsigned int status = pl011_read(uap, REG_FR);
+ /* Allow feature register bits to be inverted to work around errata */
Blank line above the comment, please.
+ unsigned int status = pl011_read(uap, REG_FR) ^ uap->vendor->inv_fr;
return status & (uap->vendor->fr_busy | UART01x_FR_TXFF) ?
0 : TIOCSER_TEMT;
}
@@ -2215,10 +2241,12 @@ pl011_console_write(struct console *co, const char *s,
unsigned int count)
uart_console_write(&uap->port, s, count, pl011_console_putchar);
/*
- * Finally, wait for transmitter to become empty
- * and restore the TCR
+ * Finally, wait for transmitter to become empty and restore the
+ * TCR. Allow feature register bits to be inverted to work around
+ * errata.
*/
- while (pl011_read(uap, REG_FR) & uap->vendor->fr_busy)
+ while ((pl011_read(uap, REG_FR) ^ uap->vendor->inv_fr)
+ & uap->vendor->fr_busy)
cpu_relax();
if (!uap->vendor->always_enabled)
pl011_write(old_cr, uap, REG_CR);
@@ -2340,8 +2368,13 @@ static int __init pl011_console_match(struct console
*co, char *name, int idx,
resource_size_t addr;
int i;
- if (strcmp(name, "pl011") != 0)
+ if (strcmp(name, "qdf2400_e44") == 0) {
+ if (!qdf2400_e44)
+ pr_info("UART: Working around QDF2400 SoC erratum 44");
Just use pr_once(), and you can skip the "if (!qdf2400_e44)". Although I don't
understand why you need to do that. pl011_console_match() should only be called
once anyway, right?
+ qdf2400_e44 = true;
+ } else if (strcmp(name, "pl011") != 0) {
return -ENODEV;
+ }
if (uart_parse_earlycon(options, &iotype, &addr, &options))
return -ENODEV;
@@ -2383,6 +2416,25 @@ static struct console amba_console = {
#define AMBA_CONSOLE (&amba_console)
+static void qdf2400_e44_putc(struct uart_port *port, int c)
+{
+ while (readl(port->membase + UART01x_FR) & UART01x_FR_TXFF)
+ cpu_relax();
+ if (port->iotype == UPIO_MEM32)
+ writel(c, port->membase + UART01x_DR);
+ else
+ writeb(c, port->membase + UART01x_DR);
I think you can ignore the UPIO_MEM32 test and always use writel(), even on the
QDF2400.
--
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the
Code Aurora Forum, hosted by The Linux Foundation.
