From: Sergiu Moga <sergiu.moga@microchip.com> To: <lee@kernel.org>, <robh+dt@kernel.org>, <krzysztof.kozlowski+dt@linaro.org>, <nicolas.ferre@microchip.com>, <alexandre.belloni@bootlin.com>, <claudiu.beznea@microchip.com>, <radu_nicolae.pirea@upb.ro>, <richard.genoud@gmail.com>, <mturquette@baylibre.com>, <sboyd@kernel.org>, <gregkh@linuxfoundation.org>, <jirislaby@kernel.org>, <admin@hifiphile.com>, <kavyasree.kotagiri@microchip.com> Cc: <devicetree@vger.kernel.org>, <linux-arm-kernel@lists.infradead.org>, <linux-kernel@vger.kernel.org>, <linux-spi@vger.kernel.org>, <linux-clk@vger.kernel.org>, <linux-serial@vger.kernel.org>, Sergiu Moga <sergiu.moga@microchip.com> Subject: [PATCH 5/5] tty: serial: atmel: Make the driver aware of the existence of GCLK Date: Wed, 17 Aug 2022 10:55:18 +0300 [thread overview] Message-ID: <20220817075517.49575-6-sergiu.moga@microchip.com> (raw) In-Reply-To: <20220817075517.49575-1-sergiu.moga@microchip.com> Previously, the atmel serial driver did not take into account the possibility of using the more customizable generic clock as its baudrate generator. Unless there is a Fractional Part available to increase accuracy, there is a high chance that we may be able to generate a baudrate closer to the desired one by using the GCLK as the clock source. Now, depending on the error rate between the desired baudrate and the actual baudrate, the serial driver will fallback on the generic clock. The generic clock must be provided in the DT node of the serial that may need a more flexible clock source. Signed-off-by: Sergiu Moga <sergiu.moga@microchip.com> --- drivers/tty/serial/atmel_serial.c | 52 ++++++++++++++++++++++++++++++- drivers/tty/serial/atmel_serial.h | 1 + 2 files changed, 52 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c index 30ba9eef7b39..0a0b46ee0955 100644 --- a/drivers/tty/serial/atmel_serial.c +++ b/drivers/tty/serial/atmel_serial.c @@ -15,6 +15,7 @@ #include <linux/init.h> #include <linux/serial.h> #include <linux/clk.h> +#include <linux/clk-provider.h> #include <linux/console.h> #include <linux/sysrq.h> #include <linux/tty_flip.h> @@ -77,6 +78,8 @@ static void atmel_stop_rx(struct uart_port *port); #endif #define ATMEL_ISR_PASS_LIMIT 256 +#define ERROR_RATE(desired_value, actual_value) \ + ((int)(100 - ((desired_value) * 100) / (actual_value))) struct atmel_dma_buffer { unsigned char *buf; @@ -110,6 +113,7 @@ struct atmel_uart_char { struct atmel_uart_port { struct uart_port uart; /* uart */ struct clk *clk; /* uart clock */ + struct clk *gclk; /* uart generic clock */ int may_wakeup; /* cached value of device_may_wakeup for times we need to disable it */ u32 backup_imr; /* IMR saved during suspend */ int break_active; /* break being received */ @@ -2115,6 +2119,8 @@ static void atmel_serial_pm(struct uart_port *port, unsigned int state, * This is called on uart_close() or a suspend event. */ clk_disable_unprepare(atmel_port->clk); + if (atmel_port->gclk && __clk_is_enabled(atmel_port->gclk)) + clk_disable_unprepare(atmel_port->gclk); break; default: dev_err(port->dev, "atmel_serial: unknown pm %d\n", state); @@ -2129,7 +2135,8 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios, { struct atmel_uart_port *atmel_port = to_atmel_uart_port(port); unsigned long flags; - unsigned int old_mode, mode, imr, quot, baud, div, cd, fp = 0; + unsigned int old_mode, mode, imr, quot, div, cd, fp = 0; + unsigned int baud, actual_baud, gclk_rate; /* save the current mode register */ mode = old_mode = atmel_uart_readl(port, ATMEL_US_MR); @@ -2288,6 +2295,37 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios, cd /= 8; mode |= ATMEL_US_USCLKS_MCK_DIV8; } + + /* + * If there is no Fractional Part, there is a high chance that + * we may be able to generate a baudrate closer to the desired one + * if we use the GCLK as the clock source driving the baudrate + * generator. + */ + if (!fp && atmel_port->gclk) { + if (__clk_is_enabled(atmel_port->gclk)) + clk_disable_unprepare(atmel_port->gclk); + clk_set_rate(atmel_port->gclk, 16 * baud); + gclk_rate = clk_get_rate(atmel_port->gclk); + actual_baud = clk_get_rate(atmel_port->clk) / (16 * cd); + if (abs(ERROR_RATE(baud, actual_baud)) > + abs(ERROR_RATE(baud, gclk_rate / 16))) { + mode |= ATMEL_US_GCLK; + + /* + * Set the Clock Divisor for GCLK to 1. + * Since we were able to generate the smallest + * multiple of the desired baudrate times 16, + * then we surely can generate a bigger multiple + * with the exact error rate for an equally increased + * CD. Thus no need to take into account + * a higher value for CD. + */ + cd = 1; + clk_prepare_enable(atmel_port->gclk); + } + } + quot = cd | fp << ATMEL_US_FP_OFFSET; if (!(port->iso7816.flags & SER_ISO7816_ENABLED)) @@ -2883,6 +2921,16 @@ static int atmel_serial_probe(struct platform_device *pdev) if (ret) goto err; + atmel_port->gclk = devm_clk_get_optional(&pdev->dev, "gclk"); + if (atmel_port->gclk) { + ret = clk_prepare_enable(atmel_port->gclk); + if (ret) { + atmel_port->gclk = NULL; + return ret; + } + clk_disable_unprepare(atmel_port->gclk); + } + ret = atmel_init_port(atmel_port, pdev); if (ret) goto err_clk_disable_unprepare; @@ -2929,6 +2977,8 @@ static int atmel_serial_probe(struct platform_device *pdev) * is used */ clk_disable_unprepare(atmel_port->clk); + if (atmel_port->gclk && __clk_is_enabled(atmel_port->gclk)) + clk_disable_unprepare(atmel_port->gclk); return 0; diff --git a/drivers/tty/serial/atmel_serial.h b/drivers/tty/serial/atmel_serial.h index 0d8a0f9cc5c3..fb718972f81a 100644 --- a/drivers/tty/serial/atmel_serial.h +++ b/drivers/tty/serial/atmel_serial.h @@ -63,6 +63,7 @@ #define ATMEL_US_PAR_MARK (3 << 9) #define ATMEL_US_PAR_NONE (4 << 9) #define ATMEL_US_PAR_MULTI_DROP (6 << 9) +#define ATMEL_US_GCLK BIT(12) #define ATMEL_US_NBSTOP GENMASK(13, 12) /* Number of Stop Bits */ #define ATMEL_US_NBSTOP_1 (0 << 12) #define ATMEL_US_NBSTOP_1_5 (1 << 12) -- 2.25.1
WARNING: multiple messages have this Message-ID (diff)
From: Sergiu Moga <sergiu.moga@microchip.com> To: <lee@kernel.org>, <robh+dt@kernel.org>, <krzysztof.kozlowski+dt@linaro.org>, <nicolas.ferre@microchip.com>, <alexandre.belloni@bootlin.com>, <claudiu.beznea@microchip.com>, <radu_nicolae.pirea@upb.ro>, <richard.genoud@gmail.com>, <mturquette@baylibre.com>, <sboyd@kernel.org>, <gregkh@linuxfoundation.org>, <jirislaby@kernel.org>, <admin@hifiphile.com>, <kavyasree.kotagiri@microchip.com> Cc: <devicetree@vger.kernel.org>, <linux-arm-kernel@lists.infradead.org>, <linux-kernel@vger.kernel.org>, <linux-spi@vger.kernel.org>, <linux-clk@vger.kernel.org>, <linux-serial@vger.kernel.org>, Sergiu Moga <sergiu.moga@microchip.com> Subject: [PATCH 5/5] tty: serial: atmel: Make the driver aware of the existence of GCLK Date: Wed, 17 Aug 2022 10:55:18 +0300 [thread overview] Message-ID: <20220817075517.49575-6-sergiu.moga@microchip.com> (raw) In-Reply-To: <20220817075517.49575-1-sergiu.moga@microchip.com> Previously, the atmel serial driver did not take into account the possibility of using the more customizable generic clock as its baudrate generator. Unless there is a Fractional Part available to increase accuracy, there is a high chance that we may be able to generate a baudrate closer to the desired one by using the GCLK as the clock source. Now, depending on the error rate between the desired baudrate and the actual baudrate, the serial driver will fallback on the generic clock. The generic clock must be provided in the DT node of the serial that may need a more flexible clock source. Signed-off-by: Sergiu Moga <sergiu.moga@microchip.com> --- drivers/tty/serial/atmel_serial.c | 52 ++++++++++++++++++++++++++++++- drivers/tty/serial/atmel_serial.h | 1 + 2 files changed, 52 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c index 30ba9eef7b39..0a0b46ee0955 100644 --- a/drivers/tty/serial/atmel_serial.c +++ b/drivers/tty/serial/atmel_serial.c @@ -15,6 +15,7 @@ #include <linux/init.h> #include <linux/serial.h> #include <linux/clk.h> +#include <linux/clk-provider.h> #include <linux/console.h> #include <linux/sysrq.h> #include <linux/tty_flip.h> @@ -77,6 +78,8 @@ static void atmel_stop_rx(struct uart_port *port); #endif #define ATMEL_ISR_PASS_LIMIT 256 +#define ERROR_RATE(desired_value, actual_value) \ + ((int)(100 - ((desired_value) * 100) / (actual_value))) struct atmel_dma_buffer { unsigned char *buf; @@ -110,6 +113,7 @@ struct atmel_uart_char { struct atmel_uart_port { struct uart_port uart; /* uart */ struct clk *clk; /* uart clock */ + struct clk *gclk; /* uart generic clock */ int may_wakeup; /* cached value of device_may_wakeup for times we need to disable it */ u32 backup_imr; /* IMR saved during suspend */ int break_active; /* break being received */ @@ -2115,6 +2119,8 @@ static void atmel_serial_pm(struct uart_port *port, unsigned int state, * This is called on uart_close() or a suspend event. */ clk_disable_unprepare(atmel_port->clk); + if (atmel_port->gclk && __clk_is_enabled(atmel_port->gclk)) + clk_disable_unprepare(atmel_port->gclk); break; default: dev_err(port->dev, "atmel_serial: unknown pm %d\n", state); @@ -2129,7 +2135,8 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios, { struct atmel_uart_port *atmel_port = to_atmel_uart_port(port); unsigned long flags; - unsigned int old_mode, mode, imr, quot, baud, div, cd, fp = 0; + unsigned int old_mode, mode, imr, quot, div, cd, fp = 0; + unsigned int baud, actual_baud, gclk_rate; /* save the current mode register */ mode = old_mode = atmel_uart_readl(port, ATMEL_US_MR); @@ -2288,6 +2295,37 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios, cd /= 8; mode |= ATMEL_US_USCLKS_MCK_DIV8; } + + /* + * If there is no Fractional Part, there is a high chance that + * we may be able to generate a baudrate closer to the desired one + * if we use the GCLK as the clock source driving the baudrate + * generator. + */ + if (!fp && atmel_port->gclk) { + if (__clk_is_enabled(atmel_port->gclk)) + clk_disable_unprepare(atmel_port->gclk); + clk_set_rate(atmel_port->gclk, 16 * baud); + gclk_rate = clk_get_rate(atmel_port->gclk); + actual_baud = clk_get_rate(atmel_port->clk) / (16 * cd); + if (abs(ERROR_RATE(baud, actual_baud)) > + abs(ERROR_RATE(baud, gclk_rate / 16))) { + mode |= ATMEL_US_GCLK; + + /* + * Set the Clock Divisor for GCLK to 1. + * Since we were able to generate the smallest + * multiple of the desired baudrate times 16, + * then we surely can generate a bigger multiple + * with the exact error rate for an equally increased + * CD. Thus no need to take into account + * a higher value for CD. + */ + cd = 1; + clk_prepare_enable(atmel_port->gclk); + } + } + quot = cd | fp << ATMEL_US_FP_OFFSET; if (!(port->iso7816.flags & SER_ISO7816_ENABLED)) @@ -2883,6 +2921,16 @@ static int atmel_serial_probe(struct platform_device *pdev) if (ret) goto err; + atmel_port->gclk = devm_clk_get_optional(&pdev->dev, "gclk"); + if (atmel_port->gclk) { + ret = clk_prepare_enable(atmel_port->gclk); + if (ret) { + atmel_port->gclk = NULL; + return ret; + } + clk_disable_unprepare(atmel_port->gclk); + } + ret = atmel_init_port(atmel_port, pdev); if (ret) goto err_clk_disable_unprepare; @@ -2929,6 +2977,8 @@ static int atmel_serial_probe(struct platform_device *pdev) * is used */ clk_disable_unprepare(atmel_port->clk); + if (atmel_port->gclk && __clk_is_enabled(atmel_port->gclk)) + clk_disable_unprepare(atmel_port->gclk); return 0; diff --git a/drivers/tty/serial/atmel_serial.h b/drivers/tty/serial/atmel_serial.h index 0d8a0f9cc5c3..fb718972f81a 100644 --- a/drivers/tty/serial/atmel_serial.h +++ b/drivers/tty/serial/atmel_serial.h @@ -63,6 +63,7 @@ #define ATMEL_US_PAR_MARK (3 << 9) #define ATMEL_US_PAR_NONE (4 << 9) #define ATMEL_US_PAR_MULTI_DROP (6 << 9) +#define ATMEL_US_GCLK BIT(12) #define ATMEL_US_NBSTOP GENMASK(13, 12) /* Number of Stop Bits */ #define ATMEL_US_NBSTOP_1 (0 << 12) #define ATMEL_US_NBSTOP_1_5 (1 << 12) -- 2.25.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-08-17 8:03 UTC|newest] Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-08-17 7:55 [PATCH 0/5] Make atmel serial driver aware of GCLK Sergiu Moga 2022-08-17 7:55 ` Sergiu Moga 2022-08-17 7:55 ` [PATCH 1/5] dt-bindings: mfd: atmel,sama5d2-flexcom: Add SPI child node ref binding Sergiu Moga 2022-08-17 7:55 ` Sergiu Moga 2022-08-18 8:31 ` Krzysztof Kozlowski 2022-08-18 8:31 ` Krzysztof Kozlowski 2022-08-17 7:55 ` [PATCH 2/5] dt-bindings: mfd: atmel,at91-usart: convert to json-schema Sergiu Moga 2022-08-17 7:55 ` Sergiu Moga 2022-08-18 8:38 ` Krzysztof Kozlowski 2022-08-18 8:38 ` Krzysztof Kozlowski 2022-08-19 8:37 ` Sergiu.Moga 2022-08-19 8:37 ` Sergiu.Moga 2022-08-19 8:41 ` Krzysztof Kozlowski 2022-08-19 8:41 ` Krzysztof Kozlowski 2022-08-19 9:25 ` Sergiu.Moga 2022-08-19 9:25 ` Sergiu.Moga 2022-08-19 12:06 ` Krzysztof Kozlowski 2022-08-19 12:06 ` Krzysztof Kozlowski 2022-08-18 8:39 ` Krzysztof Kozlowski 2022-08-18 8:39 ` Krzysztof Kozlowski 2022-08-19 8:38 ` Sergiu.Moga 2022-08-19 8:38 ` Sergiu.Moga 2022-08-19 8:47 ` Krzysztof Kozlowski 2022-08-19 8:47 ` Krzysztof Kozlowski 2022-08-19 9:05 ` Krzysztof Kozlowski 2022-08-19 9:05 ` Krzysztof Kozlowski 2022-09-01 11:31 ` Eugen.Hristev 2022-09-01 11:31 ` Eugen.Hristev 2022-09-05 10:10 ` Krzysztof Kozlowski 2022-09-05 10:10 ` Krzysztof Kozlowski 2022-09-05 14:37 ` Lee Jones 2022-09-05 14:37 ` Lee Jones 2022-09-05 15:22 ` Sergiu.Moga 2022-09-05 15:22 ` Sergiu.Moga 2022-09-05 16:12 ` Krzysztof Kozlowski 2022-09-05 16:12 ` Krzysztof Kozlowski 2022-09-06 15:49 ` Lee Jones 2022-09-06 15:49 ` Lee Jones 2022-08-17 7:55 ` [PATCH 3/5] dt-bindings: mfd: atmel,sama5d2-flexcom: Add USART child node ref binding Sergiu Moga 2022-08-17 7:55 ` Sergiu Moga 2022-08-17 7:55 ` [PATCH 4/5] clk: at91: sama5d2: Add Generic Clocks for UART/USART Sergiu Moga 2022-08-17 7:55 ` Sergiu Moga 2022-08-26 7:03 ` Claudiu.Beznea 2022-08-26 7:03 ` Claudiu.Beznea 2022-08-30 22:23 ` Stephen Boyd 2022-08-30 22:23 ` Stephen Boyd 2022-08-31 14:47 ` Claudiu.Beznea 2022-08-31 14:47 ` Claudiu.Beznea 2022-08-17 7:55 ` Sergiu Moga [this message] 2022-08-17 7:55 ` [PATCH 5/5] tty: serial: atmel: Make the driver aware of the existence of GCLK Sergiu Moga 2022-08-30 17:29 ` Richard Genoud 2022-08-30 17:29 ` Richard Genoud 2022-08-31 8:49 ` Sergiu.Moga 2022-08-31 8:49 ` Sergiu.Moga 2022-08-31 9:46 ` Claudiu.Beznea 2022-08-31 9:46 ` Claudiu.Beznea 2022-08-31 11:32 ` Sergiu.Moga 2022-08-31 11:32 ` Sergiu.Moga 2022-09-01 6:36 ` Claudiu.Beznea 2022-09-01 6:36 ` Claudiu.Beznea
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