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SubjectRe: [PATCH 2/3] drm/msm/dp: Shrink locking area of dp_aux_transfer()
On 2021-05-07 14:25, Stephen Boyd wrote:
> We don't need to hold the lock to inspect the message we're going to
> transfer, and we don't need to clear the busy flag either. Take the
> lock
> later and bail out earlier if conditions aren't met.
>
> Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> Cc: Abhinav Kumar <abhinavk@codeaurora.org>
> Cc: Kuogee Hsieh <khsieh@codeaurora.org>
> Cc: aravindh@codeaurora.org
> Cc: Sean Paul <sean@poorly.run>
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>

Reviewed-by: Kuogee Hsieh <khsieh@codeaurora.org>
> ---
> drivers/gpu/drm/msm/dp/dp_aux.c | 19 +++++++++----------
> 1 file changed, 9 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_aux.c
> b/drivers/gpu/drm/msm/dp/dp_aux.c
> index 91188466cece..b49810396513 100644
> --- a/drivers/gpu/drm/msm/dp/dp_aux.c
> +++ b/drivers/gpu/drm/msm/dp/dp_aux.c
> @@ -329,30 +329,29 @@ static ssize_t dp_aux_transfer(struct drm_dp_aux
> *dp_aux,
> ssize_t ret;
> int const aux_cmd_native_max = 16;
> int const aux_cmd_i2c_max = 128;
> - struct dp_aux_private *aux = container_of(dp_aux,
> - struct dp_aux_private, dp_aux);
> + struct dp_aux_private *aux;
>
> - mutex_lock(&aux->mutex);
> + aux = container_of(dp_aux, struct dp_aux_private, dp_aux);
>
> aux->native = msg->request & (DP_AUX_NATIVE_WRITE &
> DP_AUX_NATIVE_READ);
>
> /* Ignore address only message */
> - if ((msg->size == 0) || (msg->buffer == NULL)) {
> + if (msg->size == 0 || !msg->buffer) {
> msg->reply = aux->native ?
> DP_AUX_NATIVE_REPLY_ACK : DP_AUX_I2C_REPLY_ACK;
> - ret = msg->size;
> - goto unlock_exit;
> + return msg->size;
> }
>
> /* msg sanity check */
> - if ((aux->native && (msg->size > aux_cmd_native_max)) ||
> - (msg->size > aux_cmd_i2c_max)) {
> + if ((aux->native && msg->size > aux_cmd_native_max) ||
> + msg->size > aux_cmd_i2c_max) {
> DRM_ERROR("%s: invalid msg: size(%zu), request(%x)\n",
> __func__, msg->size, msg->request);
> - ret = -EINVAL;
> - goto unlock_exit;
> + return -EINVAL;
> }
>
> + mutex_lock(&aux->mutex);
> +
> dp_aux_update_offset_and_segment(aux, msg);
> dp_aux_transfer_helper(aux, msg, true);

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