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:
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 <akashast@xxxxxxxxxxxxxx>
Reported-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
---
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 :)
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;
+ 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);
======================================================================================
Regards,
Akash
--
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