Low speed uart on blsp1_uart0?

Products Support DragonBoard 820c
#1

Hi Guys,

I’m trying to setup blsp1_uart0(GPIO0 & GPIO1) as serial.

cat /proc/device-tree/aliases/serial3 
/soc/serial@756f000

cat /sys/bus/platform/devices/756f000.serial/uevent 
OF_NAME=serial
OF_FULLNAME=/soc/serial@756f000
OF_COMPATIBLE_0=qcom,msm-uartdm-v1.4
OF_COMPATIBLE_1=qcom,msm-uartdm
OF_COMPATIBLE_N=2
OF_ALIAS_0=serial3
MODALIAS=of:NserialT<NULL>Cqcom,msm-uartdm-v1.4Cqcom,msm-uartdm

[ 2.589597] msm_serial 7570000.serial: msm_serial: detected port #2
[ 2.589665] msm_serial 7570000.serial: uartclk = 19200000
[ 2.589758] 7570000.serial: ttyMSM2 at MMIO 0x7570000 (irq = 9, base_baud = 1200000) is a MSM
[ 2.590089] serial serial0: tty port ttyMSM2 registered
[ 2.590560] msm_serial 75b0000.serial: msm_serial: detected port #0
[ 2.590633] msm_serial 75b0000.serial: uartclk = 7372800
[ 2.590721] 75b0000.serial: ttyMSM0 at MMIO 0x75b0000 (irq = 13, base_baud = 460800) is a MSM
[ 2.590759] msm_serial: console setup on port #0
[ 4.022005] console [ttyMSM0] enabled
[ 4.027490] msm_serial: driver initialized

I have verified blsp1_qup0 as I2C & SPI. Now i’m trying to verify blsp1_uart0. blsp1_uart0 is not getting registered with msm_serial driver & i don’t see any device node.

question: BLSP1_UART0 is reserved by proprietary binary from access?

regards,
parbatha

#2

Could you provide changes you applied in the device tree so we can check?

#3

Hi Loic,

Following are changes made in dts.

— a/arch/arm64/boot/dts/qcom/apq8096-db820c.dtsi
+++ b/arch/arm64/boot/dts/qcom/apq8096-db820c.dtsi
@@ -25,6 +25,7 @@
serial0 = &blsp2_uart1;
serial1 = &blsp2_uart2;
serial2 = &blsp1_uart1;
+serial3 = &blsp1_uart0;
i2c0 = &blsp1_i2c2;
i2c1 = &blsp2_i2c1;
i2c2 = &blsp2_i2c0;
@@ -85,6 +86,14 @@
pinctrl-1 = <&blsp2_uart1_2pins_sleep>;
};
+serial@756f000 {
+label = “LS-UART2”;
+status = “okay”;
+pinctrl-names = “default”, “sleep”;
+pinctrl-0 = <&blsp1_uart0_2pins_default>;
+pinctrl-1 = <&blsp1_uart0_2pins_sleep>;
+};

// serial@75b1000 {
// label = “LS-UART0”;
// status = “okay”;
@@ -108,7 +117,7 @@
spi@07575000 {
/* On Low speed expansion */
label = “LS-SPI0”;
-status = “okay”;
+status = “disabled”;
};
i2c@075b5000 {
diff --git a/arch/arm64/boot/dts/qcom/msm8996-pins.dtsi b/arch/arm64/boot/dts/qcom/msm8996-pins.dtsi
index 29ad359e…022760c4 100644
— a/arch/arm64/boot/dts/qcom/msm8996-pins.dtsi
+++ b/arch/arm64/boot/dts/qcom/msm8996-pins.dtsi
@@ -165,6 +165,30 @@
};
};
+blsp1_uart0_2pins_default: blsp1_uart0_2pins {
+pinmux {
+function = “blsp_uart1”;
+pins = “gpio0”, “gpio1”;
+};
+pinconf {
+pins = “gpio0”, “gpio1”;
+drive-strength = <16>;
+bias-disable;
+};
+};
+
+blsp1_uart0_2pins_sleep: blsp1_uart0_2pins_sleep {
+pinmux {
+function = “gpio”;
+pins = “gpio0”, “gpio1”;
+};
+pinconf {
+pins = “gpio0”, “gpio1”;
+drive-strength = <2>;
+bias-disable;
+};
+};
+
blsp2_uart1_4pins_default: blsp2_uart1_4pins {
pinmux {
function = “blsp_uart8”;
diff --git a/arch/arm64/boot/dts/qcom/msm8996.dtsi b/arch/arm64/boot/dts/qcom/msm8996.dtsi
index 980b41a…7bfd20b 100644
— a/arch/arm64/boot/dts/qcom/msm8996.dtsi
+++ b/arch/arm64/boot/dts/qcom/msm8996.dtsi
@@ -701,6 +701,16 @@
status = “disabled”;
};
+blsp1_uart0: serial@756f000 {
+compatible = “qcom,msm-uartdm-v1.4”, “qcom,msm-uartdm”;
+reg = <0x0756f000 0x1000>;
+interrupts = <GIC_SPI 107 IRQ_TYPE_LEVEL_HIGH>;
+clocks = <&gcc GCC_BLSP1_UART1_APPS_CLK>,
+<&gcc GCC_BLSP1_AHB_CLK>;
+clock-names = “core”, “iface”;
+status = “disabled”;
+};
+

regards,
parbatha

#4

update:

I think issue is in driver side(drivers/tty/serial/msm_serial.c).

In probe:

if (unlikely(line < 0 || line >= UART_NR))
return -ENXIO;

UART_NR array_size is limited to three serial port. so fourth port fails.

static struct msm_port msm_uart_ports[] = {
{

#define UART_NR ARRAY_SIZE(msm_uart_ports)

[ 5.343010] msm_serial 756f000.serial: msm_serial: detected port #3
[ 5.343093] msm_serial 756f000.serial: uartclk = 19200000
[ 5.343196] msm_serial: probe of 756f000.serial failed with error -22

I will debug from my side.

provide input why serial port limited to three. correct me if i’m wrong.

#5

Following code change in driver fixed the issue.(/dev/ttyMSM3)

drivers/tty/serial/msm_serial.c

static struct msm_port msm_uart_ports[] = {
                        .line = 2,
                },
        },
      +{
               +.uart = {
                       +.iotype = UPIO_MEM,
                       +.ops = &msm_uart_pops,
                       +.flags = UPF_BOOT_AUTOCONF,
                       +.fifosize = 64,
                       +.line = 3,
               +},
      +},
#6

Yes this looks like old legacy code which needs to be fixed, as a quick fix you can try to add a fourth port.

#7

Great!

I assume we should change this to dynamic alloc.