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Miller" , Andreas Larsson Cc: linux-kernel@vger.kernel.org, Magnus Lindholm , Greg Kroah-Hartman , Jiri Slaby , linuxppc-dev@lists.ozlabs.org, linux-serial@vger.kernel.org Subject: [PATCH 7/7] hvc: add an M3000 firmware console backend Date: Fri, 2 Oct 2026 18:14:29 +0200 Message-ID: <20261002161515.932316-8-linmag7@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261002161515.932316-1-linmag7@gmail.com> References: <20261002161515.932316-1-linmag7@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Provide hvc0 through the IKKAKU Open Firmware pseudo-console, validating model and console properties before matching. Serialize firmware calls, keep the bounce buffer in locked mappings and poll input each open tick. Keep output buffers const and bound no-progress retries because HVC retries EAGAIN indefinitely. A stalled firmware call remains unbounded. Use the existing SPARC p1275 interface and HVC output contract. Signed-off-by: Magnus Lindholm --- MAINTAINERS | 6 ++ drivers/tty/hvc/Kconfig | 10 +++ drivers/tty/hvc/Makefile | 2 + drivers/tty/hvc/hvc_m3000.c | 167 ++++++++++++++++++++++++++++++++++++ 4 files changed, 185 insertions(+) create mode 100644 drivers/tty/hvc/hvc_m3000.c diff --git a/MAINTAINERS b/MAINTAINERS index 3a19da74d00c..5bc9b1cabd0a 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -10728,6 +10728,12 @@ L: platform-driver-x86@vger.kernel.org S: Maintained F: drivers/platform/x86/fujitsu-laptop.c +FUJITSU M3000 FIRMWARE CONSOLE +M: Magnus Lindholm +L: linux-serial@vger.kernel.org +S: Maintained +F: drivers/tty/hvc/hvc_m3000.c + FUJITSU TABLET EXTRAS M: Robert Gerlach L: platform-driver-x86@vger.kernel.org diff --git a/drivers/tty/hvc/Kconfig b/drivers/tty/hvc/Kconfig index 5866195de26a..0feb7ec98f4f 100644 --- a/drivers/tty/hvc/Kconfig +++ b/drivers/tty/hvc/Kconfig @@ -134,3 +134,13 @@ config HVCS will depend on arch specific APIs exported from hvcserver.ko which will also be compiled when this driver is built as a module. + +config HVC_M3000 + bool "M3000 firmware pseudo-console" + depends on SPARC64_VII + select HVC_DRIVER + help + Provide hvc0 using Open Firmware stdin/stdout on IKKAKU only. + Input is polled; no native UART registers are accessed. + Firmware calls are serialized and use a locked-image bounce buffer. + Say Y to use the M3000 firmware pseudo-console as hvc0. diff --git a/drivers/tty/hvc/Makefile b/drivers/tty/hvc/Makefile index 98880e357941..5b0277deb7c9 100644 --- a/drivers/tty/hvc/Makefile +++ b/drivers/tty/hvc/Makefile @@ -11,3 +11,5 @@ obj-$(CONFIG_HVC_IUCV) += hvc_iucv.o obj-$(CONFIG_HVC_UDBG) += hvc_udbg.o obj-$(CONFIG_HVC_RISCV_SBI) += hvc_riscv_sbi.o obj-$(CONFIG_HVCS) += hvcs.o + +obj-$(CONFIG_HVC_M3000) += hvc_m3000.o diff --git a/drivers/tty/hvc/hvc_m3000.c b/drivers/tty/hvc/hvc_m3000.c new file mode 100644 index 000000000000..0ef4c888a6a2 --- /dev/null +++ b/drivers/tty/hvc/hvc_m3000.c @@ -0,0 +1,167 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Experimental M3000 Open Firmware pseudo-console backend. */ +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include "hvc_console.h" + +#define M3000_WRITE_ATTEMPTS 8 + +static int m3000_stdin; +static bool m3000_ready; +/* Keep firmware buffers within the locked kernel image mappings. */ +static u8 m3000_buffer[256]; +static DEFINE_RAW_SPINLOCK(m3000_buffer_lock); +static struct timer_list m3000_poll_timer; +static bool m3000_poll_active; + +/* + * HVC's idle backoff can exceed the firmware input FIFO's capacity. + * Wake its worker each tick while open; keep PROM calls out of the timer. + */ +static void m3000_poll_tick(struct timer_list *timer) +{ + if (!READ_ONCE(m3000_poll_active)) + return; + hvc_kick(); + mod_timer(&m3000_poll_timer, jiffies + 1); +} + +static int m3000_open(struct hvc_struct *hp, int data) +{ + WRITE_ONCE(m3000_poll_active, true); + mod_timer(&m3000_poll_timer, jiffies + 1); + return 0; +} + +static void m3000_close(struct hvc_struct *hp, int data) +{ + WRITE_ONCE(m3000_poll_active, false); + timer_delete_sync(&m3000_poll_timer); +} + +static ssize_t m3000_io(u8 *in, const u8 *out, size_t count) +{ + unsigned long args[7], flags; + bool input = in != NULL; + int ret; + + if (!count) + return 0; + count = min_t(size_t, count, input ? 1 : sizeof(m3000_buffer)); + /* Serialize the bounce buffer; p1275 separately serializes firmware. */ + raw_spin_lock_irqsave(&m3000_buffer_lock, flags); + if (!input) + memcpy(m3000_buffer, out, count); + args[0] = (unsigned long)(input ? "read" : "write"); + args[1] = 3; + args[2] = 1; + args[3] = (unsigned int)(input ? m3000_stdin : prom_stdout); + args[4] = (unsigned long)m3000_buffer; + args[5] = count; + args[6] = (unsigned long)-1; + p1275_cmd_direct(args); + ret = (int)args[6]; + if (ret > 0 && ret <= count && input) + memcpy(in, m3000_buffer, ret); + raw_spin_unlock_irqrestore(&m3000_buffer_lock, flags); + if (ret == -2 || ret == 0) + return input ? 0 : -EAGAIN; + if (ret < 0 || ret > count) + return -EIO; + return ret; +} + +static ssize_t m3000_get(u32 termno, u8 *buf, size_t count) +{ + return m3000_io(buf, NULL, count); +} + +static ssize_t m3000_put(u32 termno, const u8 *buf, size_t count) +{ + ssize_t ret; + int attempt; + + /* + * HVC retries -EAGAIN forever, so drop this chunk without logging when + * the no-progress budget expires. This cannot bound a stalled firmware + * call or lock acquisition. + */ + for (attempt = 0; attempt < M3000_WRITE_ATTEMPTS; attempt++) { + ret = m3000_io(NULL, buf, count); + if (ret != -EAGAIN) + return ret; + cpu_relax(); + } + return -EIO; +} + +static const struct hv_ops m3000_ops = { + .get_chars = m3000_get, + .put_chars = m3000_put, + .notifier_add = m3000_open, + .notifier_del = m3000_close, + .notifier_hangup = m3000_close, +}; + +static bool __init m3000_property_matches(phandle node, const char *prop, + const char *expected) +{ + char value[64]; + int len; + + len = prom_getproperty(node, prop, value, sizeof(value) - 1); + if (len <= 0) + return false; + value[len] = '\0'; + return !strcmp(value, expected); +} + +static int __init m3000_console_init(void) +{ + phandle node; + int ret; + + if (tlb_type != sparc64_vii) + return -ENODEV; + if (!m3000_property_matches(prom_finddevice("/"), "model", "IKKAKU")) + return -ENODEV; + m3000_stdin = prom_getint(prom_chosen_node, "stdin"); + if (!m3000_stdin || m3000_stdin == -1 || !prom_stdout || prom_stdout == -1) + return -ENODEV; + node = prom_inst2pkg(prom_stdout); + if (!m3000_property_matches(node, "name", "pseudo-console")) + return -ENODEV; + node = prom_inst2pkg(m3000_stdin); + if (!m3000_property_matches(node, "name", "pseudo-console")) + return -ENODEV; + ret = hvc_instantiate(0, 0, &m3000_ops); + if (ret < 0) + return ret; + m3000_ready = true; + return 0; +} +console_initcall(m3000_console_init); + +static int __init m3000_tty_init(void) +{ + struct hvc_struct *hp; + + if (!m3000_ready) + return -ENODEV; + timer_setup(&m3000_poll_timer, m3000_poll_tick, 0); + hp = hvc_alloc(0, 0, &m3000_ops, sizeof(m3000_buffer)); + if (IS_ERR(hp)) + return PTR_ERR(hp); + hp->ws.ws_row = 24; + hp->ws.ws_col = 80; + pr_info("M3000: firmware-backed hvc0 tty ready (serialized, polled input)\n"); + return 0; +} +device_initcall(m3000_tty_init); -- 2.43.0