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SubjectRe: [PATCH v2 1/2] acpi, spcr: Make SPCR avialable to other architectures
From
Date
[Sorry everyone for the late response, I went away on vacation and pushed this
off until I returned.]

On 12/13/2017 07:45 AM, Lorenzo Pieralisi wrote:
> [+Mark, Graeme]
>
> In $SUBJECT, s/avialable/available
>
> On Mon, Dec 11, 2017 at 10:50:58AM -0500, Prarit Bhargava wrote:
>> Other architectures can use SPCR to setup an early console or console
>> but the current code is ARM64 specific.
>
> I see nothing ARM64 specific in current code (apart from some
> ACPICA macros with an ARM tag in them) please explain to me
> what's preventing you to reuse current code on x86.

Ah, I didn't notice that. I thought the ACPICA macros were ARM specific. I'll
rework this patchset with that in mind.

>
>> Change the name of parse_spcr() to acpi_parse_spcr(). Add a weak
>> function acpi_arch_setup_console() that can be used for arch-specific
>> setup. Move flags into ACPI code. Update the Documention on the use of
>> the SPCR.
>>
>> [v2]: Don't return an error in the baud_rate check of acpi_parse_spcr().
>> Keep ACPI_SPCR_TABLE selected for ARM64. Fix 8-bit port access width
>> mmio value. Move baud rate check earlier.
>
> This does not belong in the commit log.

Yes, but some maintainers like to see what changed between v1 & v2.

>
>> Signed-off-by: Prarit Bhargava <prarit@redhat.com>
>> Cc: linux-doc@vger.kernel.org
>> Cc: linux-kernel@vger.kernel.org
>> Cc: linux-arm-kernel@lists.infradead.org
>> Cc: linux-pm@vger.kernel.org
>> Cc: linux-acpi@vger.kernel.org
>> Cc: linux-serial@vger.kernel.org
>> Cc: Bhupesh Sharma <bhsharma@redhat.com>
>> Cc: Lv Zheng <lv.zheng@intel.com>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: "H. Peter Anvin" <hpa@zytor.com>
>> Cc: x86@kernel.org
>> Cc: Jonathan Corbet <corbet@lwn.net>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Cc: Will Deacon <will.deacon@arm.com>
>> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
>> Cc: Timur Tabi <timur@codeaurora.org>
>> ---
>> Documentation/admin-guide/kernel-parameters.txt | 6 +-
>> arch/arm64/kernel/acpi.c | 128 ++++++++++++++++-
>> drivers/acpi/Kconfig | 7 +-
>> drivers/acpi/spcr.c | 175 ++++++------------------
>> drivers/tty/serial/earlycon.c | 15 +-
>> include/linux/acpi.h | 11 +-
>> include/linux/serial_core.h | 2 -
>> 7 files changed, 184 insertions(+), 160 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index 6571fbfdb2a1..0d173289c67e 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -914,9 +914,9 @@
>>
>> earlycon= [KNL] Output early console device and options.
>>
>> - When used with no options, the early console is
>> - determined by the stdout-path property in device
>> - tree's chosen node.
>> + [ARM64] The early console is determined by the
>> + stdout-path property in device tree's chosen node,
>> + or determined by the ACPI SPCR table.
>>
>> cdns,<addr>[,options]
>> Start an early, polled-mode console on a Cadence
>> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
>> index b3162715ed78..b3e33bbdf3b7 100644
>> --- a/arch/arm64/kernel/acpi.c
>> +++ b/arch/arm64/kernel/acpi.c
>> @@ -25,7 +25,6 @@
>> #include <linux/memblock.h>
>> #include <linux/of_fdt.h>
>> #include <linux/smp.h>
>> -#include <linux/serial_core.h>
>>
>> #include <asm/cputype.h>
>> #include <asm/cpu_ops.h>
>> @@ -177,6 +176,128 @@ static int __init acpi_fadt_sanity_check(void)
>> return ret;
>> }
>>
>> +/*
>> + * 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
>> + * acpi_parse_spcr().
>> + */
>> +bool qdf2400_e44_present;
>> +EXPORT_SYMBOL(qdf2400_e44_present);
>
> My eyes, this is horrible but it is not introduced by this patch. It
> would have been much better if:
>
> drivers/tty/serial/amba-pl011.c
>
> parsed the SPCR table (again) to detect it instead of relying on this
> horrible exported flag.

It looks like Timur & you had a discussion and the current consensus is to keep
the code the same.

>
>> +
>> +/*
>> + * Some Qualcomm Datacenter Technologies SoCs have a defective UART BUSY bit.
>> + * Detect them by examining the OEM fields in the SPCR header, similar to PCI
>> + * quirk detection in pci_mcfg.c.
>> + */
>> +static bool qdf2400_erratum_44_present(struct acpi_table_header *h)
>> +{
>> + if (memcmp(h->oem_id, "QCOM ", ACPI_OEM_ID_SIZE))
>> + return false;
>> +
>> + if (!memcmp(h->oem_table_id, "QDF2432 ", ACPI_OEM_TABLE_ID_SIZE))
>> + return true;
>> +
>> + if (!memcmp(h->oem_table_id, "QDF2400 ", ACPI_OEM_TABLE_ID_SIZE) &&
>> + h->oem_revision == 1)
>> + return true;
>> +
>> + return false;
>> +}
>> +
>> +/*
>> + * APM X-Gene v1 and v2 UART hardware is an 16550 like device but has its
>> + * register aligned to 32-bit. In addition, the BIOS also encoded the
>> + * access width to be 8 bits. This function detects this errata condition.
>> + */
>> +static bool xgene_8250_erratum_present(struct acpi_table_spcr *tb)
>> +{
>> + bool xgene_8250 = false;
>> +
>> + if (tb->interface_type != ACPI_DBG2_16550_COMPATIBLE)
>> + return false;
>> +
>> + if (memcmp(tb->header.oem_id, "APMC0D", ACPI_OEM_ID_SIZE) &&
>> + memcmp(tb->header.oem_id, "HPE ", ACPI_OEM_ID_SIZE))
>> + return false;
>> +
>> + if (!memcmp(tb->header.oem_table_id, "XGENESPC",
>> + ACPI_OEM_TABLE_ID_SIZE) && tb->header.oem_revision == 0)
>> + xgene_8250 = true;
>> +
>> + if (!memcmp(tb->header.oem_table_id, "ProLiant",
>> + ACPI_OEM_TABLE_ID_SIZE) && tb->header.oem_revision == 1)
>> + xgene_8250 = true;
>> +
>> + return xgene_8250;
>> +}
>> +
>> +int acpi_arch_setup_console(struct acpi_table_spcr *table,
>> + char *opts, char *uart, char *iotype,
>> + int baud_rate, bool earlycon)
>> +{
>> + if (table->header.revision < 2) {
>> + pr_err("wrong table version\n");
>> + return -ENOENT;
>> + }
>> +
>> + switch (table->interface_type) {
>> + case ACPI_DBG2_ARM_SBSA_32BIT:
>> + snprintf(iotype, ACPI_SPCR_BUF_SIZE, "mmio32");
>> + /* fall through */
>> + case ACPI_DBG2_ARM_PL011:
>> + case ACPI_DBG2_ARM_SBSA_GENERIC:
>> + case ACPI_DBG2_BCM2835:
>> + snprintf(uart, ACPI_SPCR_BUF_SIZE, "pl011");
>> + break;
>> + default:
>> + if (strlen(uart) == 0)
>> + return -ENOENT;
>> + }
>> +
>> + /*
>> + * 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)
>> + snprintf(uart, ACPI_SPCR_BUF_SIZE, "qdf2400_e44");
>> + }
>> +
>> + if (xgene_8250_erratum_present(table)) {
>> + snprintf(iotype, ACPI_SPCR_BUF_SIZE, "mmio32");
>> +
>> + /* for xgene v1 and v2 we don't know the clock rate of the
>> + * UART so don't attempt to change to the baud rate state
>> + * in the table because driver cannot calculate the dividers
>> + */
>> + snprintf(opts, ACPI_SPCR_OPTS_SIZE, "%s,%s,0x%llx", uart,
>> + iotype, table->serial_port.address);
>> + } else {
>> + snprintf(opts, ACPI_SPCR_OPTS_SIZE, "%s,%s,0x%llx,%d", uart,
>> + iotype, table->serial_port.address, baud_rate);
>> + }
>> +
>> + return 0;
>> +}
>> +EXPORT_SYMBOL(acpi_arch_setup_console);
>
> EXPORT_SYMBOL() ? Why ?
>
> BTW, why do we need an arch hook ? I do not see anything that prevents
> you from using this code on x86 systems - is there anything arch
> specific in the SPCR specification itself ?

See above comment. But also keep in mind I have seen a lot of x86 systems that
do not define the ACPI table version correctly. The table version is 0 or 1,
and the current spec says it must be 2. It looks like ARM requires 2.

>
>> +
>> /*
>> * acpi_boot_table_init() called from setup_arch(), always.
>> * 1. find RSDP and get its address, and then find XSDT
>> @@ -230,10 +351,11 @@ void __init acpi_boot_table_init(void)
>>
>> done:
>> if (acpi_disabled) {
>> - if (earlycon_init_is_deferred)
>> + if (console_acpi_spcr_enable)
>> early_init_dt_scan_chosen_stdout();
>> } else {
>> - parse_spcr(earlycon_init_is_deferred);
>> + /* Always enable the ACPI SPCR console */
>> + acpi_parse_spcr(console_acpi_spcr_enable);
>> if (IS_ENABLED(CONFIG_ACPI_BGRT))
>> acpi_table_parse(ACPI_SIG_BGRT, acpi_parse_bgrt);
>> }
>> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
>> index 46505396869e..9ae98eeada76 100644
>> --- a/drivers/acpi/Kconfig
>> +++ b/drivers/acpi/Kconfig
>> @@ -79,7 +79,12 @@ config ACPI_DEBUGGER_USER
>> endif
>>
>> config ACPI_SPCR_TABLE
>> - bool
>> + bool "ACPI Serial Port Console Redirection Support"
>> + default y if ARM64
>
> You need to remove the selection in arch/arm64 then. Also, moving away
> from a non-visible config may have consequences on ARM64, Graeme and
> Mark are more familiar with the SPCR dependencies so please chime in.

Ok, I'll double check this.

>
>> + help
>> + Enable support for Serial Port Console Redirection (SPCR) Table.
>> + This table provides information about the configuration of the
>> + earlycon console.
>>
>> config ACPI_LPIT
>> bool
>> diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
>> index 324b35bfe781..f4bb8110e404 100644
>> --- a/drivers/acpi/spcr.c
>> +++ b/drivers/acpi/spcr.c
>> @@ -16,65 +16,18 @@
>> #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
>> - * quirk detection in pci_mcfg.c.
>> - */
>> -static bool qdf2400_erratum_44_present(struct acpi_table_header *h)
>> -{
>> - if (memcmp(h->oem_id, "QCOM ", ACPI_OEM_ID_SIZE))
>> - return false;
>> -
>> - if (!memcmp(h->oem_table_id, "QDF2432 ", ACPI_OEM_TABLE_ID_SIZE))
>> - return true;
>> -
>> - if (!memcmp(h->oem_table_id, "QDF2400 ", ACPI_OEM_TABLE_ID_SIZE) &&
>> - h->oem_revision == 1)
>> - return true;
>> -
>> - return false;
>> -}
>> -
>> -/*
>> - * APM X-Gene v1 and v2 UART hardware is an 16550 like device but has its
>> - * register aligned to 32-bit. In addition, the BIOS also encoded the
>> - * access width to be 8 bits. This function detects this errata condition.
>> - */
>> -static bool xgene_8250_erratum_present(struct acpi_table_spcr *tb)
>> +int __weak acpi_arch_setup_console(struct acpi_table_spcr *table,
>> + char *opts, char *uart, char *iotype,
>> + int baud_rate, bool earlycon)
>> {
>> - bool xgene_8250 = false;
>> -
>> - if (tb->interface_type != ACPI_DBG2_16550_COMPATIBLE)
>> - return false;
>> -
>> - if (memcmp(tb->header.oem_id, "APMC0D", ACPI_OEM_ID_SIZE) &&
>> - memcmp(tb->header.oem_id, "HPE ", ACPI_OEM_ID_SIZE))
>> - return false;
>> -
>> - if (!memcmp(tb->header.oem_table_id, "XGENESPC",
>> - ACPI_OEM_TABLE_ID_SIZE) && tb->header.oem_revision == 0)
>> - xgene_8250 = true;
>> -
>> - if (!memcmp(tb->header.oem_table_id, "ProLiant",
>> - ACPI_OEM_TABLE_ID_SIZE) && tb->header.oem_revision == 1)
>> - xgene_8250 = true;
>> -
>> - return xgene_8250;
>> + snprintf(opts, ACPI_SPCR_OPTS_SIZE, "%s,%s,0x%llx,%d", uart, iotype,
>> + table->serial_port.address, baud_rate);
>> + return 0;
>> }
>>
>> +bool console_acpi_spcr_enable __initdata;
>> /**
>> - * parse_spcr() - parse ACPI SPCR table and add preferred console
>> + * acpi_parse_spcr() - parse ACPI SPCR table and add preferred console
>> *
>> * @earlycon: set up earlycon for the console specified by the table
>> *
>> @@ -86,13 +39,13 @@ static bool xgene_8250_erratum_present(struct acpi_table_spcr *tb)
>> * from arch initialization code as soon as the DT/ACPI decision is made.
>> *
>> */
>> -int __init parse_spcr(bool earlycon)
>> +int __init acpi_parse_spcr(bool earlycon)
>> {
>> - static char opts[64];
>> + static char opts[ACPI_SPCR_OPTS_SIZE];
>> + static char uart[ACPI_SPCR_BUF_SIZE];
>> + static char iotype[ACPI_SPCR_BUF_SIZE];
>> struct acpi_table_spcr *table;
>> acpi_status status;
>> - char *uart;
>> - char *iotype;
>> int baud_rate;
>> int err;
>>
>> @@ -105,48 +58,6 @@ int __init parse_spcr(bool earlycon)
>> if (ACPI_FAILURE(status))
>> return -ENOENT;
>>
>> - if (table->header.revision < 2) {
>> - err = -ENOENT;
>> - pr_err("wrong table version\n");
>> - goto done;
>> - }
>> -
>> - if (table->serial_port.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
>> - switch (ACPI_ACCESS_BIT_WIDTH((
>> - table->serial_port.access_width))) {
>> - default:
>> - pr_err("Unexpected SPCR Access Width. Defaulting to byte size\n");
>> - case 8:
>> - iotype = "mmio";
>> - break;
>> - case 16:
>> - iotype = "mmio16";
>> - break;
>> - case 32:
>> - iotype = "mmio32";
>> - break;
>> - }
>> - } else
>> - iotype = "io";
>> -
>> - switch (table->interface_type) {
>> - case ACPI_DBG2_ARM_SBSA_32BIT:
>> - iotype = "mmio32";
>> - /* fall through */
>> - case ACPI_DBG2_ARM_PL011:
>> - case ACPI_DBG2_ARM_SBSA_GENERIC:
>> - case ACPI_DBG2_BCM2835:
>> - uart = "pl011";
>> - break;
>> - case ACPI_DBG2_16550_COMPATIBLE:
>> - case ACPI_DBG2_16550_SUBSET:
>> - uart = "uart";
>> - break;
>> - default:
>> - err = -ENOENT;
>> - goto done;
>> - }
>> -
>> switch (table->baud_rate) {
>> case 3:
>> baud_rate = 9600;
>> @@ -165,43 +76,36 @@ int __init parse_spcr(bool earlycon)
>> goto done;
>> }
>>
>> - /*
>> - * 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";
>> + switch (table->interface_type) {
>> + case ACPI_DBG2_16550_COMPATIBLE:
>> + case ACPI_DBG2_16550_SUBSET:
>> + snprintf(uart, ACPI_SPCR_BUF_SIZE, "uart");
>> + break;
>> + default:
>> + break;
>> }
>>
>> - if (xgene_8250_erratum_present(table)) {
>> - iotype = "mmio32";
>> + if (table->serial_port.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
>> + u8 width = ACPI_ACCESS_BIT_WIDTH((
>> + table->serial_port.access_width));
>> + switch (width) {
>> + default:
>> + pr_err("Unexpected SPCR Access Width. Defaulting to byte size\n");
>> + case 8:
>> + snprintf(iotype, ACPI_SPCR_BUF_SIZE, "mmio");
>> + break;
>> + case 16:
>> + case 32:
>> + snprintf(iotype, ACPI_SPCR_BUF_SIZE, "mmio%d", width);
>> + break;
>> + }
>> + } else
>> + snprintf(iotype, ACPI_SPCR_BUF_SIZE, "io");
>>
>> - /* for xgene v1 and v2 we don't know the clock rate of the
>> - * UART so don't attempt to change to the baud rate state
>> - * in the table because driver cannot calculate the dividers
>> - */
>> - snprintf(opts, sizeof(opts), "%s,%s,0x%llx", uart, iotype,
>> - table->serial_port.address);
>> - } else {
>> - snprintf(opts, sizeof(opts), "%s,%s,0x%llx,%d", uart, iotype,
>> - table->serial_port.address, baud_rate);
>> - }
>> + err = acpi_arch_setup_console(table, opts, uart, iotype, baud_rate,
>> + earlycon);
>> + if (err)
>> + goto done;
>>
>> pr_info("console: %s\n", opts);
>>
>> @@ -209,7 +113,6 @@ int __init parse_spcr(bool earlycon)
>> setup_earlycon(opts);
>>
>> err = add_preferred_console(uart, 0, opts + strlen(uart) + 1);
>> -
>
> Unintended change.
>
>> done:
>> acpi_put_table((struct acpi_table_header *)table);
>> return err;
>> diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c
>> index 4c8b80f1c688..b22afb62c7a3 100644
>> --- a/drivers/tty/serial/earlycon.c
>> +++ b/drivers/tty/serial/earlycon.c
>> @@ -196,26 +196,15 @@ int __init setup_earlycon(char *buf)
>> return -ENOENT;
>> }
>>
>> -/*
>> - * When CONFIG_ACPI_SPCR_TABLE is defined, "earlycon" without parameters in
>> - * command line does not start DT earlycon immediately, instead it defers
>> - * starting it until DT/ACPI decision is made. At that time if ACPI is enabled
>> - * call parse_spcr(), else call early_init_dt_scan_chosen_stdout()
>> - */
>> -bool earlycon_init_is_deferred __initdata;
>> -
>> /* early_param wrapper for setup_earlycon() */
>> static int __init param_setup_earlycon(char *buf)
>> {
>> int err;
>>
>> - /*
>> - * Just 'earlycon' is a valid param for devicetree earlycons;
>> - * don't generate a warning from parse_early_params() in that case
>> - */
>> + /* Just 'earlycon' is a valid param for devicetree and ACPI SPCR. */
>> if (!buf || !buf[0]) {
>> if (IS_ENABLED(CONFIG_ACPI_SPCR_TABLE)) {
>> - earlycon_init_is_deferred = true;
>> + console_acpi_spcr_enable = true;
>
> I am not familiar with this code, I would ask Graeme and Mark to check
> if this change is correct, the logic seems correct to me but I may be
> missing some corner cases.
>
>> return 0;
>> } else if (!buf) {
>> return early_init_dt_scan_chosen_stdout();
>> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
>> index dc1ebfeeb5ec..875d7327d91c 100644
>> --- a/include/linux/acpi.h
>> +++ b/include/linux/acpi.h
>> @@ -1241,10 +1241,17 @@ static inline bool acpi_has_watchdog(void) { return false; }
>> #endif
>>
>> #ifdef CONFIG_ACPI_SPCR_TABLE
>> +#define ACPI_SPCR_OPTS_SIZE 64
>> +#define ACPI_SPCR_BUF_SIZE 32
>> extern bool qdf2400_e44_present;
>> -int parse_spcr(bool earlycon);
>> +extern bool console_acpi_spcr_enable __initdata;
>> +extern int acpi_arch_setup_console(struct acpi_table_spcr *table,
>> + char *opts, char *uart, char *iotype,
>> + int baud_rate, bool earlycon);
>> +int acpi_parse_spcr(bool earlycon);
>> #else
>> -static inline int parse_spcr(bool earlycon) { return 0; }
>> +static const bool console_acpi_spcr_enable;
>
> The assignment in param_setup_earlycon won't compile.

Hmm ... I'm pretty sure it did. But I'll check that before resubmitting.

P.

>
> Lorenzo
>

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