linux-toradex.git/drivers/tty/serial/qcom_geni_serial.c, branch v4.19-rc4

tty: serial: qcom_geni_serial: Add support for flow control

2018-07-16T09:56:22+00:00

Add support for flow control functionality in the GENI serial driver
and also support for non-console higher baud rate(upto 4Mbps) usecases.

Signed-off-by: Girish Mahadevan 
Signed-off-by: Mohammed Khajapasha 
Signed-off-by: Karthikeyan Ramasubramanian 
Signed-off-by: Greg Kroah-Hartman

tty: serial: msm_geni_serial: Fix TX infinite loop

2018-05-14T11:52:35+00:00

The GENI serial driver handled transmit by leaving stuff in the
common circular buffer until it had completely caught up to the head,
then clearing it out all at once. This is a suboptimal way to do
transmit, as it leaves data in the circular buffer that could be
freed. Moreover, the logic implementing it is wrong, and it is easy to
get into a situation where the UART infinitely writes out the same buffer.

I could reproduce infinite serial output of the same buffer by running
dmesg, then hitting Ctrl-C. I believe what happened is xmit_size was
something large, marching towards a larger value. Then the generic OS
code flushed out the buffer and replaced it with two characters. Now the
xmit_size is a large value marching towards a small value, which it wasn't
expecting. The driver subtracts xmit_size (very large) from
uart_circ_chars_pending (2), underflows, and repeats ad nauseum. The
locking isn't wrong here, as the locks are held whenever the buffer is
manipulated, it's just that the driver wasn't expecting the buffer to be
flushed out from underneath it in between transmits.

This change reworks transmit to grab what it can from the circular buffer,
and then update ->tail, both fixing the underflow and freeing up space
for a smoother circular experience.

Signed-off-by: Evan Green 
Signed-off-by: Greg Kroah-Hartman

tty: serial: qcom_geni_serial: Add early console support

2018-05-14T11:44:55+00:00

Add early console support in Qualcomm Technologies Inc., GENI based
UART controller.

Signed-off-by: Karthikeyan Ramasubramanian 
Signed-off-by: Girish Mahadevan 
Reviewed-by: Stephen Boyd 
Signed-off-by: Greg Kroah-Hartman

tty: serial: qcom_geni_serial: Return IRQ_NONE for spurious interrupts

2018-05-14T11:44:55+00:00

Currently the driver returns IRQ_HANDLED when spurious interrupts happen.
This is misleading. Fix the behavior by returning IRQ_NONE for spurious
interrupts.

Signed-off-by: Karthikeyan Ramasubramanian 
Reviewed-by: Matthias Kaehlcke 
Reviewed-by: Stephen Boyd 
Signed-off-by: Greg Kroah-Hartman

tty: serial: qcom_geni_serial: Use iowrite32_rep to write to FIFO

2018-05-14T11:44:55+00:00

Use iowrite32_rep to write to the hardware FIFO so that the code does
not have to worry about the system endianness.

Signed-off-by: Karthikeyan Ramasubramanian 
Reviewed-by: Matthias Kaehlcke 
Reviewed-by: Stephen Boyd 
Signed-off-by: Greg Kroah-Hartman

tty: serial: qcom_geni_serial: Remove unnecessary memory barrier

2018-05-14T11:44:55+00:00

While initiating TX, only the register reads need to be ordered. The
register write order either is achieved due to data dependency or is
not required.

Use readl to achieve the read order and remove the unnecessary barrier.

Signed-off-by: Karthikeyan Ramasubramanian 
Reviewed-by: Evan Green 
Signed-off-by: Greg Kroah-Hartman

tty: serial: qcom_geni_serial: Initialize console port statically

2018-05-14T11:44:55+00:00

Perform static initialization of console_port since its initial state has
no run-time dependencies.

Signed-off-by: Karthikeyan Ramasubramanian 
Reviewed-by: Matthias Kaehlcke 
Reviewed-by: Stephen Boyd 
Signed-off-by: Greg Kroah-Hartman

tty: serial: qcom_geni_serial: Use min3 to find minimum of 3 values

2018-05-14T11:44:55+00:00

Use min3 helper to calculate the minimum value of 3 variables.

Signed-off-by: Karthikeyan Ramasubramanian 
Reviewed-by: Matthias Kaehlcke 
Reviewed-by: Stephen Boyd 
Signed-off-by: Greg Kroah-Hartman

tty: serial: qcom_geni_serial: Cleanup redundant code

2018-05-14T11:44:54+00:00

* Remove redundant casting while using min_t
* Remove redundant initialization of port_setup flag
* Remove redundant error checking in get_tx_fifo_size
* Remove logging redundant error code in debug messages
* Remove redundant disable_irq before free_irq

Signed-off-by: Karthikeyan Ramasubramanian 
Reviewed-by: Stephen Boyd 
Signed-off-by: Greg Kroah-Hartman

tty: serial: qcom_geni_serial: Add comments for clarification

2018-05-14T11:44:54+00:00

* Document reason for newline character counting in console_write
* Document reason for disabling IRQ in the system resume operation

Signed-off-by: Karthikeyan Ramasubramanian 
Reviewed-by: Matthias Kaehlcke 
Signed-off-by: Greg Kroah-Hartman