serial: sirf: use hrtimer for data rx
when the serial works as a bluetooth sink, due to audio realtime
requirement, the driver should have something similar with ALSA:
1. one big DMA buffer to easy the schedule jitter
2. split this big DMA buffer to multiple small periods, for each
period, we get a DMA interrupt, then push the data to userspace.
the small periods will easy the audio latency.
so ALSA generally uses a cyclic chained DMA.
but for sirfsoc, the dma hardware has the limitation: we have
only two loops in the cyclic mode, so we can only support two
small periods to switch. if we make the DMA buffer too big, we
get long latency, if we make the DMA buffer too little, we get
miss in scheduling for audio realtime.
so this patch moves to use a hrtimer to simulate the cyclic
DMA, then we can have a big buffer, and also have a timely
data push to users as the hrtimer can generate in small period
then actual HW interrupts.
with this patch, we also delete a lot of complex codes to handle
loop buffers, and RX timeout interrupt since the RX work can be
completely handled from hrtimer interrupt.
tests show using this way will make our bad audio streaming be-
come smooth.
Signed-off-by: Qipan Li <Qipan.Li@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/serial/sirfsoc_uart.h b/drivers/tty/serial/sirfsoc_uart.h
index 644f865..eb162b0 100644
--- a/drivers/tty/serial/sirfsoc_uart.h
+++ b/drivers/tty/serial/sirfsoc_uart.h
@@ -7,6 +7,7 @@
*/
#include <linux/bitops.h>
#include <linux/log2.h>
+#include <linux/hrtimer.h>
struct sirfsoc_uart_param {
const char *uart_name;
const char *port_name;
@@ -293,6 +294,7 @@
#define SIRFUART_IO_MODE BIT(0)
#define SIRFUART_DMA_MODE 0x0
+#define SIRFUART_RX_DMA_FLUSH 0x4
/* Baud Rate Calculation */
#define SIRF_USP_MIN_SAMPLE_DIV 0x1
@@ -353,8 +355,7 @@
uint_st->sirfsoc_rx_timeout)
#define SIRFUART_CTS_INT_ST(uint_st) (uint_st->sirfsoc_cts)
#define SIRFUART_RX_DMA_INT_EN(uint_en, uart_type) \
- (uint_en->sirfsoc_rx_timeout_en |\
- uint_en->sirfsoc_frm_err_en |\
+ (uint_en->sirfsoc_frm_err_en |\
uint_en->sirfsoc_rx_oflow_en |\
uint_en->sirfsoc_rxd_brk_en |\
((uart_type != SIRF_REAL_UART) ? \
@@ -369,7 +370,7 @@
#define SIRFSOC_PORT_TYPE 0xa5
/* Uart Common Use Macro*/
-#define SIRFSOC_RX_DMA_BUF_SIZE 256
+#define SIRFSOC_RX_DMA_BUF_SIZE (1024 * 32)
#define BYTES_TO_ALIGN(dma_addr) ((unsigned long)(dma_addr) & 0x3)
/* Uart Fifo Level Chk */
#define SIRFUART_TX_FIFO_SC_OFFSET 0
@@ -385,8 +386,8 @@
#define SIRFUART_RX_FIFO_CHK_SC SIRFUART_TX_FIFO_CHK_SC
#define SIRFUART_RX_FIFO_CHK_LC SIRFUART_TX_FIFO_CHK_LC
#define SIRFUART_RX_FIFO_CHK_HC SIRFUART_TX_FIFO_CHK_HC
+#define SIRFUART_RX_FIFO_MASK 0x7f
/* Indicate how many buffers used */
-#define SIRFSOC_RX_LOOP_BUF_CNT 2
/* For Fast Baud Rate Calculation */
struct sirfsoc_baudrate_to_regv {
@@ -400,7 +401,7 @@
TX_DMA_PAUSE,
};
-struct sirfsoc_loop_buffer {
+struct sirfsoc_rx_buffer {
struct circ_buf xmit;
dma_cookie_t cookie;
struct dma_async_tx_descriptor *desc;
@@ -420,17 +421,16 @@
struct dma_chan *tx_dma_chan;
dma_addr_t tx_dma_addr;
struct dma_async_tx_descriptor *tx_dma_desc;
- struct tasklet_struct rx_dma_complete_tasklet;
- struct tasklet_struct rx_tmo_process_tasklet;
unsigned int rx_io_count;
unsigned long transfer_size;
enum sirfsoc_tx_state tx_dma_state;
unsigned int cts_gpio;
unsigned int rts_gpio;
- struct sirfsoc_loop_buffer rx_dma_items[SIRFSOC_RX_LOOP_BUF_CNT];
- int rx_completed;
- int rx_issued;
+ struct sirfsoc_rx_buffer rx_dma_items;
+ struct hrtimer hrt;
+ bool is_hrt_enabled;
+ unsigned long rx_period_time;
};
/* Register Access Control */