[PATCH 2/2] soc/imx: add workaround for i.MX6QP to the GPC PD driver

[Lucas Stach]

On i.MX6QP, due to hardware erratum ERR009619, the PRE clocks may be
stalled during the power up sequencing of the PU power domain. As this
may lead to a complete loss of display output, the recommended
workaround is to keep the PU domain enabled during normal system
operation.

Implement this by rejecting the domain power down request on the
affected SoC.

Signed-off-by: Lucas Stach <l.stach at pengutronix.de>
---
 drivers/soc/imx/gpc.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/soc/imx/gpc.c b/drivers/soc/imx/gpc.c
index 4294287e5f6c..599e1e46f694 100644
--- a/drivers/soc/imx/gpc.c
+++ b/drivers/soc/imx/gpc.c
@@ -45,6 +45,7 @@ struct imx_pm_domain {
 	unsigned int reg_offs;
 	signed char cntr_pdn_bit;
 	unsigned int ipg_rate_mhz;
+	bool allow_dynamic_pd;
 };
 
 static inline struct imx_pm_domain *
@@ -59,6 +60,9 @@ static int imx6_pm_domain_power_off(struct generic_pm_domain *genpd)
 	int iso, iso2sw;
 	u32 val;
 
+	if (!pd->allow_dynamic_pd)
+		return -EBUSY;
+
 	/* Read ISO and ISO2SW power down delays */
 	regmap_read(pd->regmap, pd->reg_offs + GPC_PGC_PUPSCR_OFFS, &val);
 	iso = val & 0x3f;
@@ -255,6 +259,7 @@ static struct imx_pm_domain imx_gpc_domains[] = {
 		},
 		.reg_offs = 0x260,
 		.cntr_pdn_bit = 0,
+		.allow_dynamic_pd = true,
 	}, {
 		.base = {
 			.name = "DISPLAY",
@@ -263,23 +268,33 @@ static struct imx_pm_domain imx_gpc_domains[] = {
 		},
 		.reg_offs = 0x240,
 		.cntr_pdn_bit = 4,
+		.allow_dynamic_pd = true,
 	}
 };
 
 struct imx_gpc_dt_data {
 	int num_domains;
+	bool err009619_present;
 };
 
 static const struct imx_gpc_dt_data imx6q_dt_data = {
 	.num_domains = 2,
+	.err009619_present = false,
+};
+
+static const struct imx_gpc_dt_data imx6qp_dt_data = {
+	.num_domains = 2,
+	.err009619_present = true,
 };
 
 static const struct imx_gpc_dt_data imx6sl_dt_data = {
 	.num_domains = 3,
+	.err009619_present = false,
 };
 
 static const struct of_device_id imx_gpc_dt_ids[] = {
 	{ .compatible = "fsl,imx6q-gpc", .data = &imx6q_dt_data },
+	{ .compatible = "fsl,imx6qp-gpc", .data = &imx6qp_dt_data },
 	{ .compatible = "fsl,imx6sl-gpc", .data = &imx6sl_dt_data },
 	{ }
 };
@@ -377,6 +392,10 @@ static int imx_gpc_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	/* Disable PU power down in normal operation if ERR009619 is present */
+	if (of_id_data->err009619_present)
+		imx_gpc_domains[1].allow_dynamic_pd = false;
+
 	if (!pgc_node) {
 		ret = imx_gpc_old_dt_init(&pdev->dev, regmap,
 					  of_id_data->num_domains);
-- 
2.11.0