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Wed, 15 Apr 2020 17:31:13 -0700 (PDT) Date: Wed, 15 Apr 2020 17:31:12 -0700 From: Matthias Kaehlcke To: Akash Asthana 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, georgi.djakov@linaro.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 V4 4/9] soc: qcom-geni-se: Add interconnect support to fix earlycon crash Message-ID: <20200416003112.GA199755@google.com> References: <1586946198-13912-1-git-send-email-akashast@codeaurora.org> <1586946198-13912-5-git-send-email-akashast@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1586946198-13912-5-git-send-email-akashast@codeaurora.org> User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org Hi Akash, On Wed, Apr 15, 2020 at 03:53:13PM +0530, Akash Asthana wrote: > QUP core clock is shared among all the SE drivers present on particular > QUP wrapper, the system will reset(unclocked access) if earlycon used after > QUP core clock is put to 0 from other SE drivers before real console comes > up. > > As earlycon can't vote for it's QUP core need, to fix this add ICC > support to common/QUP wrapper driver and put vote for QUP core from > probe on behalf of earlycon and remove vote during earlycon exit call. > > Signed-off-by: Akash Asthana > Reported-by: Matthias Kaehlcke > --- > Change in V3: > - Add geni_remove_earlycon_icc_vote API that will be used by earlycon > exit function to remove ICC vote for earlyconsole. > - Remove suspend/resume hook for geni-se driver as we are no longer > removing earlyconsole ICC vote from system suspend, we are removing > from earlycon exit. > > Change in V4: > - As per Matthias comment make 'earlycon_wrapper' as static structure. > > drivers/soc/qcom/qcom-geni-se.c | 50 +++++++++++++++++++++++++++++++++++ > drivers/tty/serial/qcom_geni_serial.c | 7 +++++ > include/linux/qcom-geni-se.h | 2 ++ > 3 files changed, 59 insertions(+) > > diff --git a/drivers/soc/qcom/qcom-geni-se.c b/drivers/soc/qcom/qcom-geni-se.c > index 1527bc4..727ad2e 100644 > --- a/drivers/soc/qcom/qcom-geni-se.c > +++ b/drivers/soc/qcom/qcom-geni-se.c > @@ -90,8 +90,11 @@ struct geni_wrapper { > struct device *dev; > void __iomem *base; > struct clk_bulk_data ahb_clks[NUM_AHB_CLKS]; > + struct geni_icc_path to_core; > }; > > +static struct geni_wrapper *earlycon_wrapper; > + > #define QUP_HW_VER_REG 0x4 > > /* Common SE registers */ > @@ -781,6 +784,26 @@ int geni_icc_vote_off(struct geni_se *se) > } > EXPORT_SYMBOL(geni_icc_vote_off); > > +void geni_remove_earlycon_icc_vote(void) > +{ > + struct geni_wrapper *wrapper = earlycon_wrapper; > + struct device_node *parent = of_get_next_parent(wrapper->dev->of_node); > + struct device_node *child; > + > + for_each_child_of_node(parent, child) { > + if (of_device_is_compatible(child, "qcom,geni-se-qup")) { > + wrapper = platform_get_drvdata(of_find_device_by_node( > + child)); > + icc_put(wrapper->to_core.path); > + wrapper->to_core.path = NULL; > + } > + } > + of_node_put(parent); > + > + earlycon_wrapper = NULL; > +} > +EXPORT_SYMBOL(geni_remove_earlycon_icc_vote); > + > static int geni_se_probe(struct platform_device *pdev) > { > struct device *dev = &pdev->dev; > @@ -808,6 +831,33 @@ static int geni_se_probe(struct platform_device *pdev) > } > } > > +#ifdef CONFIG_SERIAL_EARLYCON > + 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); > + /* > + * Put minmal BW request on core clocks on behalf of early console. > + * The vote will be removed earlycon exit function. > + * > + * Note: We are putting vote on each QUP wrapper instead only to which > + * earlycon is connected because QUP core clock of different wrapper > + * share same voltage domain. If core1 is put to 0, then core2 will > + * also run at 0, if not voted. Default ICC vote will be removed ASA > + * we touch any of the core clock. > + * core1 = core2 = max(core1, core2) > + */ > + ret = icc_set_bw(wrapper->to_core.path, GENI_DEFAULT_BW, 0); > + if (ret) { > + dev_err(&pdev->dev, "%s: ICC BW voting failed for core\n", > + __func__); > + return ret; > + } > + > + if (of_get_compatible_child(pdev->dev.of_node, "qcom,geni-debug-uart")) > + earlycon_wrapper = wrapper; > + of_node_put(pdev->dev.of_node); > +#endif > + > dev_set_drvdata(dev, wrapper); > dev_dbg(dev, "GENI SE Driver probed\n"); > return devm_of_platform_populate(dev); > 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 :)