From: Jani Nikula Date: Thu, 18 May 2017 11:10:24 +0000 (+0300) Subject: drm/dp: start a DPCD based DP sink/branch device quirk database X-Git-Tag: Ubuntu-5.2.0-15.16~6767^2^2~1 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=76fa998acd86b6b40d0217e12af39c2406bdcd2b;p=mirror_ubuntu-eoan-kernel.git drm/dp: start a DPCD based DP sink/branch device quirk database Face the fact, there are Display Port sink and branch devices out there in the wild that don't follow the Display Port specifications, or they have bugs, or just otherwise require special treatment. Start a common quirk database the drivers can query based on the DP device identification. At least for now, we leave the workarounds for the drivers to implement as they see fit. For starters, add a branch device that can't handle full 24-bit main link Mdiv and Ndiv main link attributes properly. Naturally, the workaround of reducing main link attributes for all devices ended up in regressions for other devices. So here we are. v2: Rebase on DRM DP desc read helpers v3: Fix the OUI memcmp blunder (Clint) Cc: Ville Syrjälä Cc: Dhinakaran Pandiyan Cc: Clint Taylor Cc: Adam Jackson Cc: Harry Wentland Tested-by: Clinton Taylor Reviewed-by: Clinton Taylor Reviewed-by: Daniel Vetter # v2 Signed-off-by: Jani Nikula Link: http://patchwork.freedesktop.org/patch/msgid/91ec198dd95258dbf3bee2f6be739e0da73b4fdd.1495105635.git.jani.nikula@intel.com --- diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 52e0ca9a5bb1..213fb837e1c4 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -1209,6 +1209,51 @@ int drm_dp_stop_crc(struct drm_dp_aux *aux) } EXPORT_SYMBOL(drm_dp_stop_crc); +struct dpcd_quirk { + u8 oui[3]; + bool is_branch; + u32 quirks; +}; + +#define OUI(first, second, third) { (first), (second), (third) } + +static const struct dpcd_quirk dpcd_quirk_list[] = { + /* Analogix 7737 needs reduced M and N at HBR2 link rates */ + { OUI(0x00, 0x22, 0xb9), true, BIT(DP_DPCD_QUIRK_LIMITED_M_N) }, +}; + +#undef OUI + +/* + * Get a bit mask of DPCD quirks for the sink/branch device identified by + * ident. The quirk data is shared but it's up to the drivers to act on the + * data. + * + * For now, only the OUI (first three bytes) is used, but this may be extended + * to device identification string and hardware/firmware revisions later. + */ +static u32 +drm_dp_get_quirks(const struct drm_dp_dpcd_ident *ident, bool is_branch) +{ + const struct dpcd_quirk *quirk; + u32 quirks = 0; + int i; + + for (i = 0; i < ARRAY_SIZE(dpcd_quirk_list); i++) { + quirk = &dpcd_quirk_list[i]; + + if (quirk->is_branch != is_branch) + continue; + + if (memcmp(quirk->oui, ident->oui, sizeof(ident->oui)) != 0) + continue; + + quirks |= quirk->quirks; + } + + return quirks; +} + /** * drm_dp_read_desc - read sink/branch descriptor from DPCD * @aux: DisplayPort AUX channel @@ -1231,14 +1276,17 @@ int drm_dp_read_desc(struct drm_dp_aux *aux, struct drm_dp_desc *desc, if (ret < 0) return ret; + desc->quirks = drm_dp_get_quirks(ident, is_branch); + dev_id_len = strnlen(ident->device_id, sizeof(ident->device_id)); - DRM_DEBUG_KMS("DP %s: OUI %*phD dev-ID %*pE HW-rev %d.%d SW-rev %d.%d\n", + DRM_DEBUG_KMS("DP %s: OUI %*phD dev-ID %*pE HW-rev %d.%d SW-rev %d.%d quirks 0x%04x\n", is_branch ? "branch" : "sink", (int)sizeof(ident->oui), ident->oui, dev_id_len, ident->device_id, ident->hw_rev >> 4, ident->hw_rev & 0xf, - ident->sw_major_rev, ident->sw_minor_rev); + ident->sw_major_rev, ident->sw_minor_rev, + desc->quirks); return 0; } diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h index 84502da177a1..bb837310c07e 100644 --- a/include/drm/drm_dp_helper.h +++ b/include/drm/drm_dp_helper.h @@ -924,12 +924,44 @@ struct drm_dp_dpcd_ident { /** * struct drm_dp_desc - DP branch/sink device descriptor * @ident: DP device identification from DPCD 0x400 (sink) or 0x500 (branch). + * @quirks: Quirks; use drm_dp_has_quirk() to query for the quirks. */ struct drm_dp_desc { struct drm_dp_dpcd_ident ident; + u32 quirks; }; int drm_dp_read_desc(struct drm_dp_aux *aux, struct drm_dp_desc *desc, bool is_branch); +/** + * enum drm_dp_quirk - Display Port sink/branch device specific quirks + * + * Display Port sink and branch devices in the wild have a variety of bugs, try + * to collect them here. The quirks are shared, but it's up to the drivers to + * implement workarounds for them. + */ +enum drm_dp_quirk { + /** + * @DP_DPCD_QUIRK_LIMITED_M_N: + * + * The device requires main link attributes Mvid and Nvid to be limited + * to 16 bits. + */ + DP_DPCD_QUIRK_LIMITED_M_N, +}; + +/** + * drm_dp_has_quirk() - does the DP device have a specific quirk + * @desc: Device decriptor filled by drm_dp_read_desc() + * @quirk: Quirk to query for + * + * Return true if DP device identified by @desc has @quirk. + */ +static inline bool +drm_dp_has_quirk(const struct drm_dp_desc *desc, enum drm_dp_quirk quirk) +{ + return desc->quirks & BIT(quirk); +} + #endif /* _DRM_DP_HELPER_H_ */