Linux-SPI Archive on lore.kernel.org
 help / color / Atom feed
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: Tue, 17 Mar 2020 12:08:04 -0700
Message-ID: <20200317190804.GS144492@google.com> (raw)
In-Reply-To: <e9293de6-004f-6005-8cb6-66f28c080ebe@codeaurora.org>

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@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
> > >
> > > ...
> > >
> > >   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.

Unsurprisingly one of the first things the QCA BT driver does is to configure
the baudrate. It typically starts with a lower ('init') speed, and then switches
to the higher ('operational') baudrate:

https://elixir.bootlin.com/linux/v5.5.8/source/drivers/bluetooth/hci_qca.c#L1256

  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 [this message]
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
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200317190804.GS144492@google.com \
    --to=mka@chromium.org \
    --cc=agross@kernel.org \
    --cc=akashast@codeaurora.org \
    --cc=bjorn.andersson@linaro.org \
    --cc=broonie@kernel.org \
    --cc=devicetree@vger.kernel.org \
    --cc=dianders@chromium.org \
    --cc=evgreen@chromium.org \
    --cc=gregkh@linuxfoundation.org \
    --cc=linux-arm-msm@vger.kernel.org \
    --cc=linux-i2c@vger.kernel.org \
    --cc=linux-serial@vger.kernel.org \
    --cc=linux-spi@vger.kernel.org \
    --cc=mark.rutland@arm.com \
    --cc=mgautam@codeaurora.org \
    --cc=robh+dt@kernel.org \
    --cc=swboyd@chromium.org \
    --cc=wsa@the-dreams.de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-SPI Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-spi/0 linux-spi/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-spi linux-spi/ https://lore.kernel.org/linux-spi \
		linux-spi@vger.kernel.org
	public-inbox-index linux-spi

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-spi


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git