On 1/9/2023 6:47 PM, Dmitry Baryshkov wrote:
On 10/01/2023 04:40, Abhinav Kumar wrote:
On 1/9/2023 5:19 PM, Dmitry Baryshkov wrote:
On 27/10/2022 20:36, Dmitry Baryshkov wrote:
On 22/09/2022 03:49, Abhinav Kumar wrote:
Currently there is no protection against a user trying to set
an unsupported mode on DSI. Implement a check based on the opp
table whether the byte clock for the mode can be supported by
validating whether an opp table entry exists.
For devices which have not added opp table support yet, skip
this check otherwise it will break bootup on those devices.
Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/15
Reported-by: Rob Clark <robdclark@xxxxxxxxx>
Signed-off-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
---
drivers/gpu/drm/msm/dsi/dsi_manager.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/drivers/gpu/drm/msm/dsi/dsi_manager.c
b/drivers/gpu/drm/msm/dsi/dsi_manager.c
index 3a1417397283..87b518c42965 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_manager.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_manager.c
@@ -450,6 +450,29 @@ static enum drm_mode_status
dsi_mgr_bridge_mode_valid(struct drm_bridge *bridge,
int id = dsi_mgr_bridge_get_id(bridge);
struct msm_dsi *msm_dsi = dsi_mgr_get_dsi(id);
struct mipi_dsi_host *host = msm_dsi->host;
+ struct platform_device *pdev = msm_dsi->pdev;
+ struct dev_pm_opp *opp;
+ struct opp_table *opp_tbl;
+ unsigned long byte_clk_rate;
+
+ byte_clk_rate = dsi_byte_clk_get_rate(host, IS_BONDED_DSI(),
mode);
+
+ /*
+ * first check if there is an opp table available for the
calculated
+ * byte clock and then check DSC related info. Some devices
have not
+ * added support for OPP table. Skip the check for those.
+ */
+ opp_tbl = dev_pm_opp_get_opp_table(&pdev->dev);
Can we store the table inside the msm_dsi during the init? Then we
won't have to get it again and again during each mode_valid call.
I checked other drivers. I think we can skip the get_opp_table
completely, can we not? Just handle ENODEV returned from
dev_pm_opp_find_freq_ceil().
Your point is valid but I had a doubt on that API.
As per the documentation of that API, it says
639 * Return: matching *opp and refreshes *freq accordingly, else
returns
640 * ERR_PTR in case of error and should be handled using IS_ERR.
Error return
641 * values can be:
642 * EINVAL: for bad pointer
643 * ERANGE: no match found for search
644 * ENODEV: if device not found in list of registered devices
645 *
646 * The callers are required to call dev_pm_opp_put() for the
returned OPP after
647 * use.
648 */
649 struct dev_pm_opp *dev_pm_opp_find_freq_ceil(struct device *dev,
650 unsigned long *freq)
651 {
So ideally yes, ENODEV means that table was not found but .... that
API uses _find_opp_table under the hood.
which says
79 * Return: pointer to 'struct opp_table' if found, otherwise
-ENODEV or
80 * -EINVAL based on type of error.
81 *
82 * The callers must call dev_pm_opp_put_opp_table() after the table
is used.
Now, how would we know if the failure was due to table not found OR
entry not found.
Table now found means that SOC has probably not started using OPP
table which is alright and not an error.
But EINVAL could mean an entry not found which means it exceeds the
opp table limits.
I think this would be -ERANGE as documented.
EINVAL means dev is null or something of the same kind.
Okay, so EINVAL and ERANGE are genuine errors but ENODEV is not in our
case as all SOCs might not have opp table yet.
Do you still think selective handling of these two errors is better than
the current implementation? That way its separation is clear.
So there was some ambiguity on this. So I broke it down into two calls.
If my concern is invalid, let me know.
But I do agree with you that we can cache the opp table once rather
than doing it in every mode_valid().
+ if (opp_tbl) {
+ opp = dev_pm_opp_find_freq_ceil(&pdev->dev, &byte_clk_rate);
+ if (IS_ERR(opp)) {
+ pr_err("opp table not found for freq %lu err: %ld\n",
+ byte_clk_rate, PTR_ERR(opp));
+ return PTR_ERR(opp);
+ }
+ dev_pm_opp_put(opp);
+ dev_pm_opp_put_opp_table(opp_tbl);
+ }
return msm_dsi_host_check_dsc(host, mode);
}
