Re: [PATCH V2 4/8] tty: serial: qcom_geni_serial: Add interconnect support

From: Matthias Kaehlcke <mka@chromium.org>
To: Akash Asthana <akashast@codeaurora.org>
Cc: gregkh@linuxfoundation.org, agross@kernel.org,
	bjorn.andersson@linaro.org, wsa@the-dreams.de,
	broonie@kernel.org, mark.rutland@arm.com, robh+dt@kernel.org,
	linux-i2c@vger.kernel.org, linux-spi@vger.kernel.org,
	devicetree@vger.kernel.org, swboyd@chromium.org,
	mgautam@codeaurora.org, linux-arm-msm@vger.kernel.org,
	linux-serial@vger.kernel.org, dianders@chromium.org,
	evgreen@chromium.org
Subject: Re: [PATCH V2 4/8] tty: serial: qcom_geni_serial: Add interconnect support
Date: Fri, 13 Mar 2020 14:28:33 -0700	[thread overview]
Message-ID: <20200313212833.GK144492@google.com> (raw)
In-Reply-To: <1584105134-13583-5-git-send-email-akashast@codeaurora.org>

Hi Akash,

On Fri, Mar 13, 2020 at 06:42:10PM +0530, Akash Asthana wrote:
> Get the interconnect paths for Uart based Serial Engine device
> and vote according to the baud rate requirement of the driver.
> 
> Signed-off-by: Akash Asthana <akashast@codeaurora.org>
> ---
> Changes in V2:
>  - As per Bjorn's comment, removed se == NULL check from geni_serial_icc_get
>  - As per Bjorn's comment, removed code to set se->icc_path* to NULL in failure
>  - As per Bjorn's comment, introduced and using devm_of_icc_get API for getting
>    path handle
>  - As per Matthias comment, added error handling for icc_set_bw call
> 
>  drivers/tty/serial/qcom_geni_serial.c | 69 +++++++++++++++++++++++++++++++++--
>  1 file changed, 65 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
> index 272bae0..c8ad7e9 100644
> --- a/drivers/tty/serial/qcom_geni_serial.c
> +++ b/drivers/tty/serial/qcom_geni_serial.c
> @@ -184,6 +184,19 @@ static struct qcom_geni_serial_port qcom_geni_console_port = {
>  	},
>  };
>  
> +static int geni_serial_icc_get(struct geni_se *se)
> +{
> +	se->icc_path_geni_to_core = devm_of_icc_get(se->dev, "qup-core");
> +	if (IS_ERR(se->icc_path_geni_to_core))
> +		return PTR_ERR(se->icc_path_geni_to_core);
> +
> +	se->icc_path_cpu_to_geni = devm_of_icc_get(se->dev, "qup-config");
> +	if (IS_ERR(se->icc_path_cpu_to_geni))
> +		return PTR_ERR(se->icc_path_cpu_to_geni);
> +
> +	return 0;
> +}
> +
>  static int qcom_geni_serial_request_port(struct uart_port *uport)
>  {
>  	struct platform_device *pdev = to_platform_device(uport->dev);
> @@ -962,6 +975,7 @@ static void qcom_geni_serial_set_termios(struct uart_port *uport,
>  	struct qcom_geni_serial_port *port = to_dev_port(uport, uport);
>  	unsigned long clk_rate;
>  	u32 ver, sampling_rate;
> +	int ret;
>  
>  	qcom_geni_serial_stop_rx(uport);
>  	/* baud rate */
> @@ -983,6 +997,18 @@ static void qcom_geni_serial_set_termios(struct uart_port *uport,
>  	ser_clk_cfg = SER_CLK_EN;
>  	ser_clk_cfg |= clk_div << CLK_DIV_SHFT;
>  
> +	/*
> +	 * Put BW vote only on CPU path as driver supports FIFO mode only.
> +	 * Assume peak_bw as twice of avg_bw.
> +	 */
> +	port->se.avg_bw_cpu = Bps_to_icc(baud);
> +	port->se.peak_bw_cpu = Bps_to_icc(2 * baud);
> +	ret = icc_set_bw(port->se.icc_path_cpu_to_geni, port->se.avg_bw_cpu,
> +			port->se.peak_bw_cpu);
> +	if (ret)
> +		dev_err(uport->dev, "%s: ICC BW voting failed for cpu\n",
> +			__func__);

Should this return an error? The port might not operate properly if the ICC
bandwidth couldn't be configured

> +
>  	/* parity */
>  	tx_trans_cfg = readl(uport->membase + SE_UART_TX_TRANS_CFG);
>  	tx_parity_cfg = readl(uport->membase + SE_UART_TX_PARITY_CFG);
> @@ -1208,16 +1234,40 @@ static void qcom_geni_serial_pm(struct uart_port *uport,
>  		unsigned int new_state, unsigned int old_state)
>  {
>  	struct qcom_geni_serial_port *port = to_dev_port(uport, uport);
> -
> +	int ret;
>  	/* If we've never been called, treat it as off */
>  	if (old_state == UART_PM_STATE_UNDEFINED)
>  		old_state = UART_PM_STATE_OFF;
>  
> -	if (new_state == UART_PM_STATE_ON && old_state == UART_PM_STATE_OFF)
> +	if (new_state == UART_PM_STATE_ON && old_state == UART_PM_STATE_OFF) {
> +		/* Put BW vote for core clocks and CPU */
> +		ret = icc_set_bw(port->se.icc_path_geni_to_core,
> +			port->se.avg_bw_core, port->se.peak_bw_core);
> +		if (ret)
> +			dev_err(uport->dev, "%s: ICC BW voting failed for core\n",
> +				__func__);
> +
> +		ret = icc_set_bw(port->se.icc_path_cpu_to_geni,
> +			port->se.avg_bw_cpu, port->se.peak_bw_cpu);
> +		if (ret)
> +			dev_err(uport->dev, "%s: ICC BW voting failed for cpu\n",
> +				__func__);
> +
>  		geni_se_resources_on(&port->se);
> -	else if (new_state == UART_PM_STATE_OFF &&
> -			old_state == UART_PM_STATE_ON)
> +	} else if (new_state == UART_PM_STATE_OFF &&
> +			old_state == UART_PM_STATE_ON) {
>  		geni_se_resources_off(&port->se);
> +		/* Remove BW vote from core clocks and CPU */
> +		ret = icc_set_bw(port->se.icc_path_geni_to_core, 0, 0);
> +		if (ret)
> +			dev_err(uport->dev, "%s: ICC BW remove failed for core\n",
> +				__func__);
> +
> +		ret = icc_set_bw(port->se.icc_path_cpu_to_geni, 0, 0);
> +		if (ret)
> +			dev_err(uport->dev, "%s: ICC BW remove failed for cpu\n",
> +				__func__);
> +	}
>  }
>  
>  static const struct uart_ops qcom_geni_console_pops = {
> @@ -1308,6 +1358,17 @@ static int qcom_geni_serial_probe(struct platform_device *pdev)
>  	port->rx_fifo_depth = DEF_FIFO_DEPTH_WORDS;
>  	port->tx_fifo_width = DEF_FIFO_WIDTH_BITS;
>  
> +	ret = geni_serial_icc_get(&port->se);
> +	if (ret)
> +		return ret;
> +	/* Set the bus quota to a reasonable value */
> +	port->se.avg_bw_core = console ? Bps_to_icc(1000) :
> +		Bps_to_icc(CORE_2X_50_MHZ);

Why different settings for console vs. non-console?

> +	port->se.peak_bw_core = console ? Bps_to_icc(1000) :
> +		Bps_to_icc(CORE_2X_100_MHZ);
> +	port->se.avg_bw_cpu = Bps_to_icc(1000);
> +	port->se.peak_bw_cpu = Bps_to_icc(1000);

'Bps_to_icc(1000)' is a recurring theme in this series, could it be worth
to have a constant for that? Could be GENI_DEFAULT_BW or similar.