serial: stm32: get FIFO size from hwcfg register

Since STM32MP25, FIFO size could vary regarding the STM32MPxx version.
So we get this size from "hwcfgr1" register and compute threshold values
corresponding to the ratio given by reference manual.

As STM32MP1x, STM32MP25 and STM32H7 share the same compatible and STM32H7
doesn't have a register to get FIFO size, we force FIFO size to 16 in case
of zero read from hwcfgr1 register.

Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
Link: https://lore.kernel.org/r/20240112095300.2004878-5-valentin.caron@foss.st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 19a45e1b7102f8b7a8c1d6dfa54f656736442f6a..3cbb498c6ea682a9ec5267226a9d8384a65e068e 100644 (file)
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -40,63 +40,64 @@
 /* Register offsets */
 static struct stm32_usart_info __maybe_unused stm32f4_info = {
        .ofs = {
-               .isr    = 0x00,
-               .rdr    = 0x04,
-               .tdr    = 0x04,
-               .brr    = 0x08,
-               .cr1    = 0x0c,
-               .cr2    = 0x10,
-               .cr3    = 0x14,
-               .gtpr   = 0x18,
-               .rtor   = UNDEF_REG,
-               .rqr    = UNDEF_REG,
-               .icr    = UNDEF_REG,
-               .presc  = UNDEF_REG,
+               .isr            = 0x00,
+               .rdr            = 0x04,
+               .tdr            = 0x04,
+               .brr            = 0x08,
+               .cr1            = 0x0c,
+               .cr2            = 0x10,
+               .cr3            = 0x14,
+               .gtpr           = 0x18,
+               .rtor           = UNDEF_REG,
+               .rqr            = UNDEF_REG,
+               .icr            = UNDEF_REG,
+               .presc          = UNDEF_REG,
+               .hwcfgr1        = UNDEF_REG,
        },
        .cfg = {
                .uart_enable_bit = 13,
                .has_7bits_data = false,
-               .fifosize = 1,
        }
 };
 
 static struct stm32_usart_info __maybe_unused stm32f7_info = {
        .ofs = {
-               .cr1    = 0x00,
-               .cr2    = 0x04,
-               .cr3    = 0x08,
-               .brr    = 0x0c,
-               .gtpr   = 0x10,
-               .rtor   = 0x14,
-               .rqr    = 0x18,
-               .isr    = 0x1c,
-               .icr    = 0x20,
-               .rdr    = 0x24,
-               .tdr    = 0x28,
-               .presc  = UNDEF_REG,
+               .cr1            = 0x00,
+               .cr2            = 0x04,
+               .cr3            = 0x08,
+               .brr            = 0x0c,
+               .gtpr           = 0x10,
+               .rtor           = 0x14,
+               .rqr            = 0x18,
+               .isr            = 0x1c,
+               .icr            = 0x20,
+               .rdr            = 0x24,
+               .tdr            = 0x28,
+               .presc          = UNDEF_REG,
+               .hwcfgr1        = UNDEF_REG,
        },
        .cfg = {
                .uart_enable_bit = 0,
                .has_7bits_data = true,
                .has_swap = true,
-               .fifosize = 1,
        }
 };
 
 static struct stm32_usart_info __maybe_unused stm32h7_info = {
        .ofs = {
-               .cr1    = 0x00,
-               .cr2    = 0x04,
-               .cr3    = 0x08,
-               .brr    = 0x0c,
-               .gtpr   = 0x10,
-               .rtor   = 0x14,
-               .rqr    = 0x18,
-               .isr    = 0x1c,
-               .icr    = 0x20,
-               .rdr    = 0x24,
-               .tdr    = 0x28,
-               .presc  = 0x2c,
+               .cr1            = 0x00,
+               .cr2            = 0x04,
+               .cr3            = 0x08,
+               .brr            = 0x0c,
+               .gtpr           = 0x10,
+               .rtor           = 0x14,
+               .rqr            = 0x18,
+               .isr            = 0x1c,
+               .icr            = 0x20,
+               .rdr            = 0x24,
+               .tdr            = 0x28,
+               .presc          = 0x2c,
+               .hwcfgr1        = 0x3f0,
        },
        .cfg = {
                .uart_enable_bit = 0,
@@ -104,7 +105,6 @@ static struct stm32_usart_info __maybe_unused stm32h7_info = {
                .has_swap = true,
                .has_wakeup = true,
                .has_fifo = true,
-               .fifosize = 16,
        }
 };
 
@@ -1498,37 +1498,57 @@ static const struct uart_ops stm32_uart_ops = {
 #endif /* CONFIG_CONSOLE_POLL */
 };
 
-/*
- * STM32H7 RX & TX FIFO threshold configuration (CR3 RXFTCFG / TXFTCFG)
- * Note: 1 isn't a valid value in RXFTCFG / TXFTCFG. In this case,
- * RXNEIE / TXEIE can be used instead of threshold irqs: RXFTIE / TXFTIE.
- * So, RXFTCFG / TXFTCFG bitfields values are encoded as array index + 1.
- */
-static const u32 stm32h7_usart_fifo_thresh_cfg[] = { 1, 2, 4, 8, 12, 14, 16 };
+struct stm32_usart_thresh_ratio {
+       int mul;
+       int div;
+};
+
+static const struct stm32_usart_thresh_ratio stm32h7_usart_fifo_thresh_cfg[] = {
+       {1, 8}, {1, 4}, {1, 2}, {3, 4}, {7, 8}, {1, 1} };
 
-static void stm32_usart_get_ftcfg(struct platform_device *pdev, const char *p,
-                                 int *ftcfg)
+static int stm32_usart_get_thresh_value(u32 fifo_size, int index)
 {
-       u32 bytes, i;
+       return fifo_size * stm32h7_usart_fifo_thresh_cfg[index].mul /
+               stm32h7_usart_fifo_thresh_cfg[index].div;
+}
 
-       /* DT option to get RX & TX FIFO threshold (default to 8 bytes) */
+static int stm32_usart_get_ftcfg(struct platform_device *pdev, struct stm32_port *stm32port,
+                                const char *p, int *ftcfg)
+{
+       const struct stm32_usart_offsets *ofs = &stm32port->info->ofs;
+       u32 bytes, i, cfg8;
+       int fifo_size;
+
+       if (WARN_ON(ofs->hwcfgr1 == UNDEF_REG))
+               return 1;
+
+       cfg8 = FIELD_GET(USART_HWCFGR1_CFG8,
+                        readl_relaxed(stm32port->port.membase + ofs->hwcfgr1));
+
+       /* On STM32H7, hwcfgr is not present, so returned value will be 0 */
+       fifo_size = cfg8 ? 1 << cfg8 : STM32H7_USART_FIFO_SIZE;
+
+       /* DT option to get RX & TX FIFO threshold (default to half fifo size) */
        if (of_property_read_u32(pdev->dev.of_node, p, &bytes))
-               bytes = 8;
+               bytes = fifo_size / 2;
+
+       if (bytes < stm32_usart_get_thresh_value(fifo_size, 0)) {
+               *ftcfg = -EINVAL;
+               return fifo_size;
+       }
 
-       for (i = 0; i < ARRAY_SIZE(stm32h7_usart_fifo_thresh_cfg); i++)
-               if (stm32h7_usart_fifo_thresh_cfg[i] >= bytes)
+       for (i = 0; i < ARRAY_SIZE(stm32h7_usart_fifo_thresh_cfg); i++) {
+               if (stm32_usart_get_thresh_value(fifo_size, i) >= bytes)
                        break;
+       }
        if (i >= ARRAY_SIZE(stm32h7_usart_fifo_thresh_cfg))
                i = ARRAY_SIZE(stm32h7_usart_fifo_thresh_cfg) - 1;
 
-       dev_dbg(&pdev->dev, "%s set to %d bytes\n", p,
-               stm32h7_usart_fifo_thresh_cfg[i]);
+       dev_dbg(&pdev->dev, "%s set to %d/%d bytes\n", p,
+               stm32_usart_get_thresh_value(fifo_size, i), fifo_size);
 
-       /* Provide FIFO threshold ftcfg (1 is invalid: threshold irq unused) */
-       if (i)
-               *ftcfg = i - 1;
-       else
-               *ftcfg = -EINVAL;
+       *ftcfg = i;
+       return fifo_size;
 }
 
 static void stm32_usart_deinit_port(struct stm32_port *stm32port)
@@ -1558,7 +1578,6 @@ static int stm32_usart_init_port(struct stm32_port *stm32port,
        port->flags     = UPF_BOOT_AUTOCONF;
        port->ops       = &stm32_uart_ops;
        port->dev       = &pdev->dev;
-       port->fifosize  = stm32port->info->cfg.fifosize;
        port->has_sysrq = IS_ENABLED(CONFIG_SERIAL_STM32_CONSOLE);
        port->irq = irq;
        port->rs485_config = stm32_usart_config_rs485;
@@ -1574,14 +1593,6 @@ static int stm32_usart_init_port(struct stm32_port *stm32port,
        stm32port->swap = stm32port->info->cfg.has_swap &&
                of_property_read_bool(pdev->dev.of_node, "rx-tx-swap");
 
-       stm32port->fifoen = stm32port->info->cfg.has_fifo;
-       if (stm32port->fifoen) {
-               stm32_usart_get_ftcfg(pdev, "rx-threshold",
-                                     &stm32port->rxftcfg);
-               stm32_usart_get_ftcfg(pdev, "tx-threshold",
-                                     &stm32port->txftcfg);
-       }
-
        port->membase = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
        if (IS_ERR(port->membase))
                return PTR_ERR(port->membase);
@@ -1604,6 +1615,15 @@ static int stm32_usart_init_port(struct stm32_port *stm32port,
                goto err_clk;
        }
 
+       stm32port->fifoen = stm32port->info->cfg.has_fifo;
+       if (stm32port->fifoen) {
+               stm32_usart_get_ftcfg(pdev, stm32port, "rx-threshold", &stm32port->rxftcfg);
+               port->fifosize = stm32_usart_get_ftcfg(pdev, stm32port, "tx-threshold",
+                                                      &stm32port->txftcfg);
+       } else {
+               port->fifosize = 1;
+       }
+
        stm32port->gpios = mctrl_gpio_init(&stm32port->port, 0);
        if (IS_ERR(stm32port->gpios)) {
                ret = PTR_ERR(stm32port->gpios);

diff --git a/drivers/tty/serial/stm32-usart.h b/drivers/tty/serial/stm32-usart.h
index bf3720948704efbcf18d9e6c585854fc7d8983f3..af20258ccc7a0fcc57a541b37efcc9848290e141 100644 (file)
--- a/drivers/tty/serial/stm32-usart.h
+++ b/drivers/tty/serial/stm32-usart.h
@@ -21,6 +21,7 @@ struct stm32_usart_offsets {
        u16 rdr;
        u16 tdr;
        u16 presc;
+       u16 hwcfgr1;
 };
 
 struct stm32_usart_config {
@@ -29,7 +30,6 @@ struct stm32_usart_config {
        bool has_swap;
        bool has_wakeup;
        bool has_fifo;
-       int fifosize;
 };
 
 struct stm32_usart_info {
@@ -182,8 +182,12 @@ struct stm32_usart_info {
 #define USART_PRESC            GENMASK(3, 0)   /* H7 */
 #define USART_PRESC_MAX                0b1011
 
+/* USART_HWCFCR1 */
+#define USART_HWCFGR1_CFG8     GENMASK(31, 28) /* MP1 */
+
 #define STM32_SERIAL_NAME "ttySTM"
 #define STM32_MAX_PORTS 9
+#define STM32H7_USART_FIFO_SIZE 16
 
 #define RX_BUF_L 4096           /* dma rx buffer length     */
 #define RX_BUF_P (RX_BUF_L / 2)         /* dma rx buffer period     */