4.20-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit bd4905a9583c760da31ded7256dca6f71483c3dc ]
[WHY] On customer board, there is one pluse (1v , < 1ms) on DDC_CLK pin when plug / unplug DP cable. Driver will read it and config DP to HDMI/DVI dongle.
[HOW] If there is a real dongle, DDC_CLK should be always pull high. Try to read again to recovery this special case. Retry times = 3. Need additional 3ms to detect DP passive dongle(3 failures)
Signed-off-by: Paul Hsieh paul.hsieh@amd.com Reviewed-by: Eric Yang eric.yang2@amd.com Acked-by: Leo Li sunpeng.li@amd.com Signed-off-by: Alex Deucher alexander.deucher@amd.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/amd/display/dc/core/dc_link.c | 23 ++++++++++++++----- 1 file changed, 17 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c index 5141c1401889..ef1b350a45e0 100644 --- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c @@ -332,7 +332,7 @@ bool dc_link_is_dp_sink_present(struct dc_link *link) { enum gpio_result gpio_result; uint32_t clock_pin = 0; - + uint8_t retry = 0; struct ddc *ddc;
enum connector_id connector_id = @@ -361,11 +361,22 @@ bool dc_link_is_dp_sink_present(struct dc_link *link) return present; }
- /* Read GPIO: DP sink is present if both clock and data pins are zero */ - /* [anaumov] in DAL2, there was no check for GPIO failure */ - - gpio_result = dal_gpio_get_value(ddc->pin_clock, &clock_pin); - ASSERT(gpio_result == GPIO_RESULT_OK); + /* + * Read GPIO: DP sink is present if both clock and data pins are zero + * + * [W/A] plug-unplug DP cable, sometimes customer board has + * one short pulse on clk_pin(1V, < 1ms). DP will be config to HDMI/DVI + * then monitor can't br light up. Add retry 3 times + * But in real passive dongle, it need additional 3ms to detect + */ + do { + gpio_result = dal_gpio_get_value(ddc->pin_clock, &clock_pin); + ASSERT(gpio_result == GPIO_RESULT_OK); + if (clock_pin) + udelay(1000); + else + break; + } while (retry++ < 3);
present = (gpio_result == GPIO_RESULT_OK) && !clock_pin;