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drm/tegra: dsi: Adjust D-PHY timing

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Compliance testing shows that HS Trail is off by -12%. Increase the HS
Trail time to make this test pass.

Signed-off-by: David Ung <davidu@nvidia.com>
[treding@nvidia.com: update specification references, add comment]
Signed-off-by: Thierry Reding <treding@nvidia.com>
This commit is contained in:
David Ung 2014-12-05 15:30:05 -08:00 committed by Thierry Reding
parent 201106d83e
commit 2dafd63682
1 changed files with 19 additions and 6 deletions
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25
drivers/gpu/drm/tegra/mipi-phy.c
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@ -12,9 +12,9 @@
#include "mipi-phy.h"
/*
* Default D-PHY timings based on MIPI D-PHY specification. Derived from
* the valid ranges specified in Section 5.9 of the D-PHY specification
* with minor adjustments.
* Default D-PHY timings based on MIPI D-PHY specification. Derived from the
* valid ranges specified in Section 6.9, Table 14, Page 40 of the D-PHY
* specification (v1.2) with minor adjustments.
*/
int mipi_dphy_timing_get_default(struct mipi_dphy_timing *timing,
unsigned long period)
@ -34,7 +34,20 @@ int mipi_dphy_timing_get_default(struct mipi_dphy_timing *timing,
timing->hszero = 145 + 5 * period;
timing->hssettle = 85 + 6 * period;
timing->hsskip = 40;
timing->hstrail = max(8 * period, 60 + 4 * period);
/*
* The MIPI D-PHY specification (Section 6.9, v1.2, Table 14, Page 40)
* contains this formula as:
*
* T_HS-TRAIL = max(n * 8 * period, 60 + n * 4 * period)
*
* where n = 1 for forward-direction HS mode and n = 4 for reverse-
* direction HS mode. There's only one setting and this function does
* not parameterize on anything other that period, so this code will
* assumes that reverse-direction HS mode is supported and uses n = 4.
*/
timing->hstrail = max(4 * 8 * period, 60 + 4 * 4 * period);
timing->init = 100000;
timing->lpx = 60;
timing->taget = 5 * timing->lpx;
@ -46,8 +59,8 @@ int mipi_dphy_timing_get_default(struct mipi_dphy_timing *timing,
}
/*
* Validate D-PHY timing according to MIPI Alliance Specification for D-PHY,
* Section 5.9 "Global Operation Timing Parameters".
* Validate D-PHY timing according to MIPI D-PHY specification (v1.2, Section
* Section 6.9 "Global Operation Timing Parameters").
*/
int mipi_dphy_timing_validate(struct mipi_dphy_timing *timing,
unsigned long period)