Commit 37ef38f3 authored by Timur Tabi's avatar Timur Tabi Committed by Greg Kroah-Hartman
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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.

Fixes: 5a0722b8 ("tty: pl011: use "qdf2400_e44" as the earlycon name for QDF2400 E44")
Tested-by: default avatarJeffrey Hugo <jhugo@codeaurora.org>
Signed-off-by: default avatarTimur Tabi <timur@codeaurora.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 520eccdf

drivers/acpi/spcr.c

+34 −2
Original line number Diff line number Diff line
@@ -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
@@ -147,8 +157,30 @@ int __init parse_spcr(bool earlycon) 
		goto done;

	}



	if (qdf2400_erratum_44_present(&table->header))

	/*

	 * 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";

	}



	if (xgene_8250_erratum_present(table))

		iotype = "mmio32";

drivers/tty/serial/amba-pl011.c

+19 −18
Original line number Diff line number Diff line
@@ -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,
@@ -2375,12 +2368,14 @@ 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;
@@ -2734,11 +2729,17 @@ 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;

include/linux/acpi.h

+1 −0
Original line number Diff line number Diff line
@@ -1209,6 +1209,7 @@ 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; }

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