Re: [PATCH] drm/dp: Correctly mask DP_TRAINING_AUX_RD_INTERVAL values for DP 1.4

Rodrigo Vivi
2018-03-14T20:59:11Z

On Wed, Mar 14, 2018 at 01:20:06PM -0700, matthew.s.atwood@intel.com wrote:
> From: Matt Atwood <matthew.s.atwood@intel.com>
>
> DP_TRAINING_AUX_RD_INTERVAL with DP 1.3 spec changed bit scheeme from 8
> bits to 7 in DPCD 0x000e. The 8th bit is used to identify extended
> receiver capabilities. For panels that use this new feature wait interval
> would be increased by 512 ms, when spec is max 16 ms. This behavior is
> described in table 2-158 of DP 1.4 spec address 0000eh.
>
> With the introduction of DP 1.4 spec main link clock recovery was
> standardized to 100 us regardless of TRAINING_AUX_RD_INTERVAL value.
>
> To avoid breaking panels that are not spec compiant we now warn on
> invalid values.
>
> V2: commit title/message, masking all 7 bits, warn on out of spec values.
> V3: commit message, make link train clock recovery follow DP 1.4 spec.
> V4: style changes
> V5: typo
> V6: print statement revisions, DP_REV to DPCD_REV, comment correction
> V7: typo

https://patchwork.freedesktop.org/series/39473/
Checkpatch noticed few lines like this over 80 char.

>
> Signed-off-by: Matt Atwood <matthew.s.atwood@intel.com>
> ---
> drivers/gpu/drm/drm_dp_helper.c | 18 ++++++++++++++----
> include/drm/drm_dp_helper.h | 6 ++++++
> 2 files changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index adf79be..793c0ff 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -119,18 +119,28 @@ u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SI
> EXPORT_SYMBOL(drm_dp_get_adjust_request_pre_emphasis);
>
> void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
> - if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0)
> + int rd_interval = dpcd[DP_TRAINING_AUX_RD_INTERVAL] & DP_TRAINING_AUX_RD_MASK;

int rd_interval = dpcd[DP_TRAINING_AUX_RD_INTERVAL] &
DP_TRAINING_AUX_RD_MASK;

> +
> + if (rd_interval > 4)
> + DRM_DEBUG_KMS("AUX interval %d, out of range (max 4)\n", rd_interval);

DRM_DEBUG_KMS("AUX interval %d, out of range (max 4)\n",
rd_interval);

> +
> + if (rd_interval == 0 || (dpcd[DP_DPCD_REV] >= DPCD_REV_14))
> udelay(100);
> else
> - mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4);
> + mdelay(rd_interval * 4);
> }
> EXPORT_SYMBOL(drm_dp_link_train_clock_recovery_delay);
>
> void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
> - if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0)
> + int rd_interval = dpcd[DP_TRAINING_AUX_RD_INTERVAL] & DP_TRAINING_AUX_RD_MASK;

ditto

> +
> + if (rd_interval > 4)
> + DRM_DEBUG_KMS("AUX interval %d, out of range (max 4)\n", rd_interval);

ditto

> +
> + if (rd_interval == 0)
> udelay(400);
> else
> - mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4);
> + mdelay(rd_interval * 4);
> }
> EXPORT_SYMBOL(drm_dp_link_train_channel_eq_delay);
>
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index da58a42..9afea9f 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -64,6 +64,11 @@
> /* AUX CH addresses */
> /* DPCD */
> #define DP_DPCD_REV 0x000
> +# define DPCD_REV_10 0x10
> +# define DPCD_REV_11 0x11
> +# define DPCD_REV_12 0x12
> +# define DPCD_REV_13 0x13
> +# define DPCD_REV_14 0x14

DP_DPCD_REV_ to match the reg name

>
> #define DP_MAX_LINK_RATE 0x001
>
> @@ -118,6 +123,7 @@
> # define DP_DPCD_DISPLAY_CONTROL_CAPABLE (1 << 3) /* edp v1.2 or higher */
>
> #define DP_TRAINING_AUX_RD_INTERVAL 0x00e /* XXX 1.2? */
> +# define DP_TRAINING_AUX_RD_MASK 0x7F /* XXX 1.2 */

maybe add "?" to be in sync with the reg offset?

>
> #define DP_ADAPTER_CAP 0x00f /* 1.2 */
> # define DP_FORCE_LOAD_SENSE_CAP (1 << 0)
> --
> 2.7.4
>
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