docs/misc/xen-command-line.pandoc | 7 +++- xen/drivers/char/ns16550.c | 67 ++++++++++++++++++++----------- 2 files changed, 49 insertions(+), 25 deletions(-)
RISC-V doesn't support interrupts for the time being, so it would be nice to
have polling mode.
To force poll mode it was added parsing of new 'poll' property under "com1="
If there is no interrupt property in UART node, then polling will be used.
According to 4.2.2 National Semiconductor 16450/16550 Compatible UART
Requirements from The Devicetree Specification v0.4
( https://www.devicetree.org/specifications/ ) the interrupt property is
optional.
Also, it is possible that interrupt '0' can be used for some architectures as
an legal UART interrupt number ( according to dts files in Linux kernel ), so
the check of the return value of platform_get_irq() was updated in case of when
device tree is used for UART initialization.
For example:
https://github.com/torvalds/linux/blob/master/arch/powerpc/boot/dts/ebony.dts#L197
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
---
Changes in V5:
- Update xen-command-line.pandoc.
- move poll check to ns16550_uart_dt_init as in case of device tree
initialization it is needed only to check if 'poll' is present in com1.
- Don't init uart->irq in case when platform_get_irq() return negative value.
---
Changes in V4:
- fix code style for ns16550_irq().
- partially revert changes in pci_uart_config().
- add check of "poll" property under "com<N>=" instead of "console=".
- remove seting of polling mode in parsing of msi in parse_positional().
- update comment above opt_com1 about Configuration string of serial port.
---
docs/misc/xen-command-line.pandoc | 7 +++-
xen/drivers/char/ns16550.c | 67 ++++++++++++++++++++-----------
2 files changed, 49 insertions(+), 25 deletions(-)
diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc
index 4060ebdc5d..67e355dab8 100644
--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -331,9 +331,12 @@ Interrupts. Specifying zero disables CMCI handling.
Flag to indicate whether to probe for a CMOS Real Time Clock irrespective of
ACPI indicating none to be there.
+### com1 (device tree based initialization)
+> `= [poll]`
+
### com1 (x86)
### com2 (x86)
-> `= <baud>[/<base-baud>][,[DPS][,[<io-base>|pci|amt][,[<irq>|msi][,[<port-bdf>][,[<bridge-bdf>]]]]]]`
+> `= <baud>[/<base-baud>][,[DPS][,[<io-base>|pci|amt][,[<irq>|msi|poll][,[<port-bdf>][,[<bridge-bdf>]]]]]]`
Both option `com1` and `com2` follow the same format.
@@ -353,7 +356,7 @@ Both option `com1` and `com2` follow the same format.
* `S` is an integer 1 or 2 for the number of stop bits.
* `<io-base>` is an integer which specifies the IO base port for UART
registers.
-* `<irq>` is the IRQ number to use, or `0` to use the UART in poll
+* `<irq>` is the IRQ number to use, or `poll` to use the UART in poll
mode only, or `msi` to set up a Message Signaled Interrupt.
* `<port-bdf>` is the PCI location of the UART, in
`<bus>:<device>.<function>` notation.
diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
index 2aed6ec707..d8cfbbfae4 100644
--- a/xen/drivers/char/ns16550.c
+++ b/xen/drivers/char/ns16550.c
@@ -58,7 +58,11 @@ static struct ns16550 {
struct timer timer;
struct timer resume_timer;
unsigned int timeout_ms;
- bool_t intr_works;
+ enum {
+ intr_off,
+ intr_on,
+ polling,
+ } intr_works;
bool_t dw_usr_bsy;
#ifdef NS16550_PCI
/* PCI card parameters. */
@@ -112,6 +116,19 @@ struct ns16550_config_param {
static void enable_exar_enhanced_bits(const struct ns16550 *uart);
#endif
+/*
+ * Configure serial port with a string:
+ * <baud>[/<base_baud>][,DPS[,<io-base>[,<irq>|msi|poll[,<port-bdf>[,<bridge-bdf>]]]]].
+ * The tail of the string can be omitted if platform defaults are sufficient.
+ * If the baud rate is pre-configured, perhaps by a bootloader, then 'auto'
+ * can be specified in place of a numeric baud rate. Polled mode is specified
+ * by poll property.
+ */
+static char __initdata opt_com1[128] = "";
+static char __initdata opt_com2[128] = "";
+string_param("com1", opt_com1);
+string_param("com2", opt_com2);
+
static void cf_check ns16550_delayed_resume(void *data);
static u8 ns_read_reg(const struct ns16550 *uart, unsigned int reg)
@@ -181,7 +198,7 @@ static void cf_check ns16550_interrupt(
struct serial_port *port = dev_id;
struct ns16550 *uart = port->uart;
- uart->intr_works = 1;
+ uart->intr_works = intr_on;
while ( !(ns_read_reg(uart, UART_IIR) & UART_IIR_NOINT) )
{
@@ -212,7 +229,7 @@ static void cf_check __ns16550_poll(struct cpu_user_regs *regs)
struct serial_port *port = this_cpu(poll_port);
struct ns16550 *uart = port->uart;
- if ( uart->intr_works )
+ if ( uart->intr_works == intr_on )
return; /* Interrupts work - no more polling */
while ( ns_read_reg(uart, UART_LSR) & UART_LSR_DR )
@@ -305,7 +322,8 @@ static void ns16550_setup_preirq(struct ns16550 *uart)
unsigned char lcr;
unsigned int divisor;
- uart->intr_works = 0;
+ if ( uart->intr_works != polling )
+ uart->intr_works = intr_off;
pci_serial_early_init(uart);
@@ -394,7 +412,7 @@ static void __init cf_check ns16550_init_irq(struct serial_port *port)
static void ns16550_setup_postirq(struct ns16550 *uart)
{
- if ( uart->irq > 0 )
+ if ( uart->intr_works != polling )
{
/* Master interrupt enable; also keep DTR/RTS asserted. */
ns_write_reg(uart,
@@ -473,6 +491,7 @@ static void __init cf_check ns16550_init_postirq(struct serial_port *port)
if ( rc )
{
uart->irq = 0;
+ uart->intr_works = polling;
if ( msi_desc )
msi_free_irq(msi_desc);
else
@@ -488,7 +507,7 @@ static void __init cf_check ns16550_init_postirq(struct serial_port *port)
}
#endif
- if ( uart->irq > 0 )
+ if ( uart->intr_works != polling )
{
uart->irqaction.handler = ns16550_interrupt;
uart->irqaction.name = "ns16550";
@@ -595,7 +614,8 @@ static void __init cf_check ns16550_endboot(struct serial_port *port)
static int __init cf_check ns16550_irq(struct serial_port *port)
{
struct ns16550 *uart = port->uart;
- return ((uart->irq > 0) ? uart->irq : -1);
+
+ return ((uart->intr_works != polling) ? uart->irq : -1);
}
static void cf_check ns16550_start_tx(struct serial_port *port)
@@ -1333,9 +1353,13 @@ pci_uart_config(struct ns16550 *uart, bool_t skip_amt, unsigned int idx)
uart->irq = 0;
#endif
if ( !uart->irq )
+ {
+ uart->intr_works = polling;
+
printk(XENLOG_INFO
"ns16550: %pp: no legacy IRQ, using poll mode\n",
&PCI_SBDF(0, b, d, f));
+ }
return 0;
}
@@ -1374,19 +1398,6 @@ static void enable_exar_enhanced_bits(const struct ns16550 *uart)
#endif /* CONFIG_HAS_PCI */
-/*
- * Configure serial port with a string:
- * <baud>[/<base_baud>][,DPS[,<io-base>[,<irq>[,<port-bdf>[,<bridge-bdf>]]]]].
- * The tail of the string can be omitted if platform defaults are sufficient.
- * If the baud rate is pre-configured, perhaps by a bootloader, then 'auto'
- * can be specified in place of a numeric baud rate. Polled mode is specified
- * by requesting irq 0.
- */
-static char __initdata opt_com1[128] = "";
-static char __initdata opt_com2[128] = "";
-string_param("com1", opt_com1);
-string_param("com2", opt_com2);
-
enum serial_param_type {
baud,
clock_hz,
@@ -1555,6 +1566,9 @@ static bool __init parse_positional(struct ns16550 *uart, char **str)
}
else
#endif
+ if ( strncmp(conf, "poll", 4) == 0 )
+ uart->intr_works = polling;
+ else
uart->irq = simple_strtol(conf, &conf, 10);
}
@@ -1760,6 +1774,9 @@ static int __init ns16550_uart_dt_init(struct dt_device_node *dev,
ns16550_init_common(uart);
+ if ( strstr(opt_com1, "poll") )
+ uart->intr_works = polling;
+
uart->baud = BAUD_AUTO;
uart->data_bits = 8;
uart->parity = UART_PARITY_NONE;
@@ -1791,9 +1808,13 @@ static int __init ns16550_uart_dt_init(struct dt_device_node *dev,
}
res = platform_get_irq(dev, 0);
- if ( ! res )
- return -EINVAL;
- uart->irq = res;
+ if ( res < 0 )
+ {
+ printk("there is no interrupt property, polling will be used\n");
+ uart->intr_works = polling;
+ }
+ else
+ uart->irq = res;
uart->dw_usr_bsy = dt_device_is_compatible(dev, "snps,dw-apb-uart");
--
2.41.0
On 11.08.2023 17:30, Oleksii Kurochko wrote: > @@ -1555,6 +1566,9 @@ static bool __init parse_positional(struct ns16550 *uart, char **str) > } > else > #endif > + if ( strncmp(conf, "poll", 4) == 0 ) > + uart->intr_works = polling; Don't you need to update "conf" here as well then? As said before, please also update parse_namevalue_pairs(). I would appreciate (but not insist) if you also added recognition of "msi" at this occasion. > + else > uart->irq = simple_strtol(conf, &conf, 10); > } > > @@ -1760,6 +1774,9 @@ static int __init ns16550_uart_dt_init(struct dt_device_node *dev, > > ns16550_init_common(uart); > > + if ( strstr(opt_com1, "poll") ) > + uart->intr_works = polling; Is strstr() really appropriate? Shouldn't it simply be strcmp(), with there not being any other sub-options in the non-x86 case? Plus the question remains of it necessarily being com1: Is there no way with DT to have multiple serial ports (e.g. one for the console and one for a debugger)? If there indeed isn't, then unconditionally using opt_com1[] here is of course okay, but then opt_com2[] is effectively a dead variable and recognizing "com2" on the command line (rather than spitting out an error) is then also a mistake. IOW in that case both would want keeping x86-only (with a new #ifdef, as we certainly don't want to have com1 and com2 stuff in separate places). Jan
On Wed, 2023-08-16 at 15:39 +0200, Jan Beulich wrote: > On 11.08.2023 17:30, Oleksii Kurochko wrote: > > @@ -1555,6 +1566,9 @@ static bool __init parse_positional(struct > > ns16550 *uart, char **str) > > } > > else > > #endif > > + if ( strncmp(conf, "poll", 4) == 0 ) > > + uart->intr_works = polling; > > Don't you need to update "conf" here as well then? Yes, sure, 'conf' shoud be updated too. > > As said before, please also update parse_namevalue_pairs(). I would > appreciate (but not insist) if you also added recognition of "msi" > at this occasion. I'll add 'msi' too. > > > + else > > uart->irq = simple_strtol(conf, &conf, 10); > > } > > > > @@ -1760,6 +1774,9 @@ static int __init ns16550_uart_dt_init(struct > > dt_device_node *dev, > > > > ns16550_init_common(uart); > > > > + if ( strstr(opt_com1, "poll") ) > > + uart->intr_works = polling; > > Is strstr() really appropriate? Shouldn't it simply be strcmp(), with > there not being any other sub-options in the non-x86 case? It would better to use strcmp(). Thanks. > > Plus the question remains of it necessarily being com1: Is there no > way with DT to have multiple serial ports (e.g. one for the console > and one for a debugger)? If there indeed isn't, then unconditionally > using opt_com1[] here is of course okay, but then opt_com2[] > is effectively a dead variable and recognizing "com2" on the command > line (rather than spitting out an error) is then also a mistake. IOW > in that case both would want keeping x86-only (with a new #ifdef, as > we certainly don't want to have com1 and com2 stuff in separate > places). Actually it can be even more serial ports. For example, I have a board with 3 UARTs ( serial ports ). In this case, it looks that I should have 3 variable of opt_com{1-3}[]? Taking into account that opt_com{1-2} variables are needed only for configuration of serial ports in X86 ( in DT-based architectures all configuration info is inside a node of UART ) then we can check only opt_com1[]. ~ Oleksii
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