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charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org On Wed, Mar 18, 2020 at 05:53:22PM +0530, Akash Asthana wrote: > Hi Matthias, > > On 3/18/2020 12:38 AM, Matthias Kaehlcke wrote: > > On Tue, Mar 17, 2020 at 05:18:34PM +0530, Akash Asthana wrote: > > > Hi Matthias, > > > > > > On 3/14/2020 2:58 AM, Matthias Kaehlcke wrote: > > > > 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 > > > > > --- > > > > > 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 > > > > > > > > > > ... > > > > > > > > > > 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 > > > This is void function we can't return error from here. I guess it would be > > > somewhat okay if BW voting failed for CPU path but clk_set_rate failure is > > > more serious which is called from this function, I don't think it can be > > > move to somewhere else. > > ok, I missed that _set_termios() is void. > > > > > > > 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? > > > QUP FW runs on core clock. To support higher throughput we want FW to run at > > > higher speed. > > > > > > Since Console operate at 115200bps and BT operate at 3.2Mbps baud. We are > > > voting higher on core for BT usecase. > > > > > > These value are recommended from HW team. > > IIUC none of the values you mention are set in stone. 115200bps seems to be a > > 'standard' value for the serial console, but it could be a different baudrate. > > I guess you are referring to Qualcomm Bluetooth controllers, which are only one > > of many things that could be connected to the port. And what happens when a > > QCA BT controller is connected to a non-geni/QCA port, which doesn't know about > > its 'requirements'? The answer is that both the BT controller and the serial > > console configure the baudrate they need, hence using different values in > > _probe() is pointless. > > Are you refering other UART drivers(not based on geni HW) as non-geni/QCA > port? > > We are not scaling core BW request based on real time need like we are doing > for other paths(CPU/DDR) instead we are using some fail proof value because, > FW runs on core clock and core behaves a bit different than other NOCs. > > We don't have any functional relation which maps actual throughput > requirement to core frequency need. In the past we faced few latency issues > because of core slowness (Although it was running much higher than actual > throughput requirement). To avoid such scenario we are using recommend value > from HW team. These fix value can support SE drivers operating at their max > possible speed(4Mbps in case of non-console). ok, I missed that the core clocks aren't scaled based on the configured baudrate. Apparently experience shows that it is not practical due to the latency issues you mention. > I agree that 115200bps seems to be a 'standard' value for the serial > console, but it could be a different baudrate. > > We are voting 1000 in case of console because it  has low power mode > use-case in android, where voting CORE_2X_50_MHZ can be reported as a power > issue. > > Actually we wanted to vote 960 for console but that is not possible with > current ICC design where the minimum value is 1000bps.  So any way core is > running at 50 MHz as 1000 crosses the threshold for 19.2 MHz (960) > > only with console. Thanks for the clarification. So if a board wanted to use a higher baudrate for the console it (currently) shouldn't be a problem. While it would be nice to have uniform settings for all UARTs it's also not a big deal to have two values, just wanted to make sure it's needed