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* [Intel-gfx] [PATCH v2 1/2] drm/dp: Factor out a function to probe a DPCD address
@ 2022-04-08 17:21 Imre Deak
  2022-04-08 17:21 ` [Intel-gfx] [PATCH v2 2/2] drm/i915/dp: Add workaround for spurious AUX timeouts/hotplugs on LTTPR links Imre Deak
                   ` (13 more replies)
  0 siblings, 14 replies; 25+ messages in thread
From: Imre Deak @ 2022-04-08 17:21 UTC (permalink / raw)
  To: intel-gfx; +Cc: dri-devel

Factor out from drm_dp_dpcd_read() a function to probe a DPCD address
with a 1-byte read access. This will be needed by the next patch doing a
read from an LTTPR address, which must happen without the preceding
wake-up read in drm_dp_dpcd_read().

v2: Add a probe function instead of exporting drm_dp_dpcd_access(). (Jani)

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Imre Deak <imre.deak@intel.com>
---
 drivers/gpu/drm/dp/drm_dp.c    | 28 +++++++++++++++++++++++++---
 include/drm/dp/drm_dp_helper.h |  1 +
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/dp/drm_dp.c b/drivers/gpu/drm/dp/drm_dp.c
index 580016a1b9eb7..b58e30132768d 100644
--- a/drivers/gpu/drm/dp/drm_dp.c
+++ b/drivers/gpu/drm/dp/drm_dp.c
@@ -527,6 +527,29 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
 	return ret;
 }
 
+/**
+ * drm_dp_dpcd_probe() - probe a given DPCD address with a 1-byte read access
+ * @aux: DisplayPort AUX channel (SST)
+ * @offset: address of the register to probe
+ *
+ * Probe the provided DPCD address by reading 1 byte from it. The function can
+ * be used to trigger some side-effect the read access has, like waking up the
+ * sink, without the need for the read-out value.
+ *
+ * Returns 0 if the read access suceeded, or a negative error code on failure.
+ */
+int drm_dp_dpcd_probe(struct drm_dp_aux *aux, unsigned int offset)
+{
+	u8 buffer;
+	int ret;
+
+	ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, &buffer, 1);
+	WARN_ON(ret == 0);
+
+	return ret < 0 ? ret : 0;
+}
+EXPORT_SYMBOL(drm_dp_dpcd_probe);
+
 /**
  * drm_dp_dpcd_read() - read a series of bytes from the DPCD
  * @aux: DisplayPort AUX channel (SST or MST)
@@ -559,9 +582,8 @@ ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
 	 * monitor doesn't power down exactly after the throw away read.
 	 */
 	if (!aux->is_remote) {
-		ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV,
-					 buffer, 1);
-		if (ret != 1)
+		ret = drm_dp_dpcd_probe(aux, DP_DPCD_REV);
+		if (ret < 0)
 			goto out;
 	}
 
diff --git a/include/drm/dp/drm_dp_helper.h b/include/drm/dp/drm_dp_helper.h
index 1eccd97419436..91af98e6617c6 100644
--- a/include/drm/dp/drm_dp_helper.h
+++ b/include/drm/dp/drm_dp_helper.h
@@ -2053,6 +2053,7 @@ struct drm_dp_aux {
 	bool is_remote;
 };
 
+int drm_dp_dpcd_probe(struct drm_dp_aux *aux, unsigned int offset);
 ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
 			 void *buffer, size_t size);
 ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
-- 
2.30.2


^ permalink raw reply related	[flat|nested] 25+ messages in thread

end of thread, other threads:[~2022-04-26 14:24 UTC | newest]

Thread overview: 25+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-04-08 17:21 [Intel-gfx] [PATCH v2 1/2] drm/dp: Factor out a function to probe a DPCD address Imre Deak
2022-04-08 17:21 ` [Intel-gfx] [PATCH v2 2/2] drm/i915/dp: Add workaround for spurious AUX timeouts/hotplugs on LTTPR links Imre Deak
2022-04-08 22:46   ` [Intel-gfx] [PATCH v3 " Imre Deak
2022-04-14 10:49     ` Jani Nikula
2022-04-26  9:49       ` Imre Deak
2022-04-26 11:31         ` Jani Nikula
2022-04-26 11:59           ` Imre Deak
2022-04-26 14:23             ` Jani Nikula
2022-04-08 21:12 ` [Intel-gfx] ✗ Fi.CI.SPARSE: warning for series starting with [v2,1/2] drm/dp: Factor out a function to probe a DPCD address Patchwork
2022-04-08 21:43 ` [Intel-gfx] ✗ Fi.CI.BAT: failure " Patchwork
2022-04-08 22:47 ` [Intel-gfx] [v2, 1/2] " Almahallawy, Khaled
2022-04-08 23:02   ` Imre Deak
2022-04-08 23:22 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for series starting with [v2,1/2] drm/dp: Factor out a function to probe a DPCD address (rev2) Patchwork
2022-04-08 23:24 ` [Intel-gfx] ✗ Fi.CI.SPARSE: " Patchwork
2022-04-08 23:50 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2022-04-09  1:17 ` [Intel-gfx] ✗ Fi.CI.IGT: failure " Patchwork
2022-04-11 13:25 ` [Intel-gfx] [PATCH v3 1/2] drm/dp: Factor out a function to probe a DPCD address Imre Deak
2022-04-14 10:30   ` Jani Nikula
2022-04-11 17:02 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for series starting with [v3,1/2] drm/dp: Factor out a function to probe a DPCD address (rev3) Patchwork
2022-04-11 17:02 ` [Intel-gfx] ✗ Fi.CI.SPARSE: " Patchwork
2022-04-11 17:22 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2022-04-11 20:18 ` [Intel-gfx] ✗ Fi.CI.IGT: failure " Patchwork
2022-04-14 18:32   ` Imre Deak
2022-04-14 21:18     ` Vudum, Lakshminarayana
2022-04-14 20:13 ` [Intel-gfx] ✓ Fi.CI.IGT: success " Patchwork

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