Hi Akash,
On Tue, Apr 28, 2020 at 03:51:44PM +0530, Akash Asthana wrote:
> Hi Matthias,
>
> On 4/16/2020 6:01 AM, Matthias Kaehlcke wrote:
> > Hi Akash,
> >
> > On Wed, Apr 15, 2020 at 03:53:13PM +0530, Akash Asthana wrote:
...
> > > diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
> > > index 6119090..8c5d97c 100644
> > > --- a/drivers/tty/serial/qcom_geni_serial.c
> > > +++ b/drivers/tty/serial/qcom_geni_serial.c
> > > @@ -1090,6 +1090,12 @@ static void qcom_geni_serial_earlycon_write(struct console *con,
> > > __qcom_geni_serial_console_write(&dev->port, s, n);
> > > }
> > > +static int qcom_geni_serial_earlycon_exit(struct console *con)
> > > +{
> > > + geni_remove_earlycon_icc_vote();
> > > + return 0;
> > > +}
> > > +
> > > static int __init qcom_geni_serial_earlycon_setup(struct earlycon_device *dev,
> > > const char *opt)
> > > {
> > > @@ -1135,6 +1141,7 @@ static int __init qcom_geni_serial_earlycon_setup(struct earlycon_device *dev,
> > > writel(stop_bit_len, uport->membase + SE_UART_TX_STOP_BIT_LEN);
> > > dev->con->write = qcom_geni_serial_earlycon_write;
> > > + dev->con->exit = qcom_geni_serial_earlycon_exit;
> > The idea of using the exit handler of the early console to remove the
> > votes seemed appealing at first, however it has a drawback: the bandwidth
> > requests in geni_se_probe() are always made when CONFIG_SERIAL_EARLYCON=y,
> > also when the system doesn't actually use an early console. On such a
> > system the votes would never be removed.
> >
> > A possible alternative could seem to remove the vote at the end of
> > qcom_geni_serial_probe() of the 'normal' console, but it has a similar
> > problem: the system could not even have a normal console. One could
> > possibly argue that CONFIG_SERIAL_QCOM_GENI_CONSOLE shouldn't be set
> > on such a system, however it could be enabled to have a console for
> > development, and in production the same kernel config is used, but
> > with the console disabled through the device tree.
> >
> > I don't really have a good idea at this point, maybe we just need
> > something as ugly as a delayed work to remove the votes. Other
> > suggestions are welcome :)
>
> I think we can do something like below. Before voting we are checking
> whether earlyconsole ("qcom_geni") exits or not. The name is fixed from
> earlycon declaration file@drivers/tty/serial/qcom_geni_serial.c
>
> OF_EARLYCON_DECLARE(qcom_geni, "qcom,geni-debug-uart",
> qcom_geni_serial_earlycon_setup);
>
> ====================================================================================
>
> @@ -809,6 +809,8 @@ static int geni_se_probe(struct platform_device *pdev)
> struct device *dev = &pdev->dev;
> struct resource *res;
> struct geni_wrapper *wrapper;
> + struct console *bcon = NULL;
nit: initialization is not needed
> + int earlycon_present = 0;
> int ret;
>
> wrapper = devm_kzalloc(dev, sizeof(*wrapper), GFP_KERNEL);
> @@ -832,6 +834,15 @@ static int geni_se_probe(struct platform_device *pdev)
> }
>
> #ifdef CONFIG_SERIAL_EARLYCON
> + if (console_drivers)
> + for_each_console(bcon)
> + if (!strcmp(bcon->name, "qcom_geni")) {
> + earlycon_present = 1;
> + break;
> + }
> + if(!earlycon_present)
> + goto exit;
> +
> wrapper->to_core.path = devm_of_icc_get(dev, "qup-core");
> if (IS_ERR(wrapper->to_core.path))
> return PTR_ERR(wrapper->to_core.path);
> @@ -858,6 +869,7 @@ static int geni_se_probe(struct platform_device *pdev)
> of_node_put(pdev->dev.of_node);
> #endif
>
> +exit:
> dev_set_drvdata(dev, wrapper);
> dev_dbg(dev, "GENI SE Driver probed\n");
> return devm_of_platform_populate(dev);
>
This should work as long as the early console is always set up before
geni_se is probed, which seems a safe assumption.
