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From: Akash Asthana <akashast-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
To: Matthias Kaehlcke <mka-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
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Subject: Re: [PATCH V2 4/8] tty: serial: qcom_geni_serial: Add interconnect support
Date: Fri, 20 Mar 2020 16:05:06 +0530
Message-ID: <a886cbae-310c-a7d7-7cfc-a693422ce570@codeaurora.org> (raw)
In-Reply-To: <20200319204248.GA204494-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>

Hi Matthias,

On 3/20/2020 2:12 AM, Matthias Kaehlcke wrote:
> 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 <akashast-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.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
>>>>>>
>>>>>> ...
>>>>>>
>>>>>>     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.
Yeah That is correct.
>> 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

Okay, but I would like to keep as it is with above mentioned reason.


Thanks,

Akash

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,\na Linux Foundation Collaborative Project

  parent reply index

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-13 13:12 [PATCH V2 0/8] Add interconnect support to QSPI and QUP drivers Akash Asthana
     [not found] ` <1584105134-13583-1-git-send-email-akashast-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2020-03-13 13:12   ` [PATCH V2 1/8] interconnect: Add devm_of_icc_get() as exported API for users Akash Asthana
2020-03-13 16:26     ` Matthias Kaehlcke
2020-03-27 23:02     ` Bjorn Andersson
2020-03-13 13:12   ` [PATCH V2 4/8] tty: serial: qcom_geni_serial: Add interconnect support Akash Asthana
     [not found]     ` <1584105134-13583-5-git-send-email-akashast-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2020-03-13 21:28       ` Matthias Kaehlcke
     [not found]         ` <20200313212833.GK144492-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2020-03-17 11:48           ` Akash Asthana
2020-03-17 19:08             ` Matthias Kaehlcke
2020-03-18 12:23               ` Akash Asthana
     [not found]                 ` <e95bd6e0-d1fd-9d13-47df-f7d08b443e37-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2020-03-19 20:42                   ` Matthias Kaehlcke
     [not found]                     ` <20200319204248.GA204494-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2020-03-20 10:35                       ` Akash Asthana [this message]
2020-03-13 13:12   ` [PATCH V2 5/8] i2c: i2c-qcom-geni: " Akash Asthana
2020-03-14  0:17     ` Matthias Kaehlcke
2020-03-17 11:51       ` Akash Asthana
2020-03-13 13:12   ` [PATCH V2 6/8] spi: spi-geni-qcom: " Akash Asthana
     [not found]     ` <1584105134-13583-7-git-send-email-akashast-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2020-03-13 13:16       ` Mark Brown
2020-03-17  9:35         ` Akash Asthana
     [not found]           ` <aa197568-3bac-6962-d39d-3261f68c0514-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2020-03-17 13:06             ` Mark Brown
2020-03-20 13:52               ` Akash Asthana
2020-03-14  0:41     ` Matthias Kaehlcke
     [not found]       ` <20200314004106.GM144492-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2020-03-17 12:11         ` Akash Asthana
2020-03-13 13:12 ` [PATCH V2 2/8] soc: qcom: geni: Support for ICC voting Akash Asthana
2020-03-13 16:42   ` Matthias Kaehlcke
     [not found]     ` <20200313164207.GH144492-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2020-03-17  9:58       ` Akash Asthana
2020-03-17 19:06   ` Evan Green
     [not found]     ` <74851dda-296d-cdc5-2449-b9ec59bbc057@codeaurora.org>
2020-03-20 16:45       ` Evan Green
2020-03-27  5:33         ` Akash Asthana
2020-03-13 13:12 ` [PATCH V2 3/8] soc: qcom-geni-se: Add interconnect support to fix earlycon crash Akash Asthana
2020-03-13 20:44   ` Matthias Kaehlcke
     [not found]     ` <20200313204441.GJ144492-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2020-03-17 10:57       ` Akash Asthana
     [not found]         ` <1f86fdf0-df7c-4e4a-d4d8-8b0162e52cb4-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2020-03-17 18:29           ` Matthias Kaehlcke
2020-03-18  8:54             ` Akash Asthana
2020-03-19 19:43               ` Matthias Kaehlcke
     [not found]                 ` <20200319194332.GA60149-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2020-03-20 10:22                   ` Akash Asthana
2020-03-20 16:30                     ` Evan Green
2020-03-27  5:04                       ` Akash Asthana
2020-03-27 23:23                       ` Bjorn Andersson
2020-03-31 10:55                         ` Akash Asthana
2020-03-17 19:08           ` Evan Green
2020-03-17 19:46             ` Doug Anderson
     [not found]             ` <CAE=gft5GcOeQ5kh1bGen_P0J98g2XaAJ7NrDsxkirDoLtL4GWg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2020-03-18 10:57               ` Akash Asthana
2020-03-18 16:22                 ` Evan Green
2020-03-13 13:12 ` [PATCH V2 7/8] spi: spi-qcom-qspi: Add interconnect support Akash Asthana
2020-03-14  0:58   ` Matthias Kaehlcke
     [not found]     ` <20200314005817.GN144492-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2020-03-17 12:13       ` Akash Asthana
2020-03-17 19:08         ` Evan Green
2020-03-18 13:48           ` Akash Asthana
     [not found]             ` <e2ee1a60-a379-5c78-355a-64aad451a944-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2020-03-18 16:30               ` Evan Green
2020-03-20  5:35                 ` Akash Asthana
2020-03-13 13:12 ` [PATCH V2 8/8] arm64: dts: sc7180: Add interconnect for QUP and QSPI Akash Asthana

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