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SubjectRe: [PATCH v3 07/15] drm/bridge: tc358767: Simplify AUX data write
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On 05.06.2019 09:04, Andrey Smirnov wrote:
> Simplify AUX data write by dropping index arithmetic and shifting and
> replacing it with a call to a helper function that does three things:
>
> 1. Copies user-provided data into a write buffer
> 2. Optionally fixes the endianness of the write buffer (not needed
> on LE hosts)
> 3. Transfers contenst of the write buffer to up to 4 32-bit
> registers on the chip
>
> Note that separate data endianness fix:
>
> tmp = (tmp << 8) | buf[i];
>
> that was reserved for DP_AUX_I2C_WRITE looks really strange, since it
> will place data differently depending on the passed user-data
> size. E.g. for a write of 1 byte, data transferred to the chip would
> look like:
>
> [byte0] [dummy1] [dummy2] [dummy3]
>
> whereas for a write of 4 bytes we'd get:
>
> [byte3] [byte2] [byte1] [byte0]
>
> Since there's no indication in the datasheet that I2C write buffer
> should be treated differently than AUX write buffer and no comment in
> the original code explaining why it was done this way, that special
> I2C write buffer transformation was dropped in this patch.
>
> Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
> Cc: Archit Taneja <architt@codeaurora.org>
> Cc: Andrzej Hajda <a.hajda@samsung.com>
> Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
> Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
> Cc: Andrey Gusakov <andrey.gusakov@cogentembedded.com>
> Cc: Philipp Zabel <p.zabel@pengutronix.de>
> Cc: Cory Tusar <cory.tusar@zii.aero>
> Cc: Chris Healy <cphealy@gmail.com>
> Cc: Lucas Stach <l.stach@pengutronix.de>
> Cc: dri-devel@lists.freedesktop.org
> Cc: linux-kernel@vger.kernel.org
> ---
> drivers/gpu/drm/bridge/tc358767.c | 59 +++++++++++++++++++------------
> 1 file changed, 37 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
> index da47d81e7109..260fbcd0271e 100644
> --- a/drivers/gpu/drm/bridge/tc358767.c
> +++ b/drivers/gpu/drm/bridge/tc358767.c
> @@ -321,6 +321,32 @@ static int tc_aux_get_status(struct tc_data *tc, u8 *reply)
> return 0;
> }
>
> +static int tc_aux_write_data(struct tc_data *tc, const void *data,
> + size_t size)
> +{
> + u32 auxwdata[DP_AUX_MAX_PAYLOAD_BYTES / sizeof(u32)] = { 0 };
> + int ret, i, count = DIV_ROUND_UP(size, sizeof(u32));
> +
> + memcpy(auxwdata, data, size);
> +
> + for (i = 0; i < count; i++) {
> + /*
> + * Our regmap is configured as LE
> + * for register data, so we need
> + * undo any byte swapping that will
> + * happened to preserve original
> + * byte order.
> + */
> + cpu_to_le32s(&auxwdata[i]);
> + }
> +
> + ret = regmap_bulk_write(tc->regmap, DP0_AUXWDATA(0), auxwdata, count);
> + if (ret)
> + return ret;
> +
> + return size;
> +}


As prevoiusly maybe regmap_raw_write.

Beside this:

Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>

 --
Regards
Andrzej


> +
> static int tc_aux_read_data(struct tc_data *tc, void *data, size_t size)
> {
> u32 auxrdata[DP_AUX_MAX_PAYLOAD_BYTES / sizeof(u32)];
> @@ -350,9 +376,6 @@ static ssize_t tc_aux_transfer(struct drm_dp_aux *aux,
> struct tc_data *tc = aux_to_tc(aux);
> size_t size = min_t(size_t, 8, msg->size);
> u8 request = msg->request & ~DP_AUX_I2C_MOT;
> - u8 *buf = msg->buffer;
> - u32 tmp = 0;
> - int i = 0;
> int ret;
>
> if (size == 0)
> @@ -362,25 +385,17 @@ static ssize_t tc_aux_transfer(struct drm_dp_aux *aux,
> if (ret)
> return ret;
>
> - if (request == DP_AUX_I2C_WRITE || request == DP_AUX_NATIVE_WRITE) {
> - /* Store data */
> - while (i < size) {
> - if (request == DP_AUX_NATIVE_WRITE)
> - tmp = tmp | (buf[i] << (8 * (i & 0x3)));
> - else
> - tmp = (tmp << 8) | buf[i];
> - i++;
> - if (((i % 4) == 0) || (i == size)) {
> - ret = regmap_write(tc->regmap,
> - DP0_AUXWDATA((i - 1) >> 2),
> - tmp);
> - if (ret)
> - return ret;
> - tmp = 0;
> - }
> - }
> - } else if (request != DP_AUX_I2C_READ &&
> - request != DP_AUX_NATIVE_READ) {
> + switch (request) {
> + case DP_AUX_NATIVE_READ:
> + case DP_AUX_I2C_READ:
> + break;
> + case DP_AUX_NATIVE_WRITE:
> + case DP_AUX_I2C_WRITE:
> + ret = tc_aux_write_data(tc, msg->buffer, size);
> + if (ret < 0)
> + return ret;
> + break;
> + default:
> return -EINVAL;
> }
>


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