linux-kernel - Re: [PATCH] drm/bridge/synopsys: dsi: Add read feature

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Date:   Mon, 5 Feb 2018 12:52:19 +0000
From:   Philippe CORNU <philippe.cornu@...com>
To:     Andrzej Hajda <a.hajda@...sung.com>,
        Archit Taneja <architt@...eaurora.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        David Airlie <airlied@...ux.ie>,
        "Brian Norris" <briannorris@...omium.org>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Bhumika Goyal <bhumirks@...il.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Sandy Huang <hjc@...k-chips.com>,
        Heiko Stubner <heiko@...ech.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-rockchip@...ts.infradead.org" 
        <linux-rockchip@...ts.infradead.org>
CC:     Yannick FERTRE <yannick.fertre@...com>,
        Vincent ABRIOU <vincent.abriou@...com>,
        Alexandre TORGUE <alexandre.torgue@...com>
Subject: Re: [PATCH] drm/bridge/synopsys: dsi: Add read feature

Hi Andrzej,

And many thanks
Philippe :-)

On 02/05/2018 11:07 AM, Andrzej Hajda wrote:
> On 04.02.2018 22:31, Philippe Cornu wrote:
>> This patch adds the DCS/GENERIC DSI read feature.
>>
>> Signed-off-by: Philippe Cornu <philippe.cornu@...com>
> 
> Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>
> 
> If there will be no objections I will merge it at the end of the week.
> 
>   --
> Regards
> Andrzej
> 
>> ---
>> Extra notes:
>> DSI read tests have been performed with DCS & GENERIC, short & long
>> commands, on two different panels.
>> The maximum fifo size (32*32-bit = 128 bytes on stm32) has been
>> verified too.
>>
>>   drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 58 +++++++++++++++++++++------
>>   1 file changed, 45 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>> index e9422d05e897..65aeb3f78b48 100644
>> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>> @@ -397,18 +397,46 @@ static int dw_mipi_dsi_write(struct dw_mipi_dsi *dsi,
>>   	return dw_mipi_dsi_gen_pkt_hdr_write(dsi, le32_to_cpu(word));
>>   }
>>   
>> +static int dw_mipi_dsi_read(struct dw_mipi_dsi *dsi,
>> +			    const struct mipi_dsi_msg *msg)
>> +{
>> +	int i, j, ret, len = msg->rx_len;
>> +	u8 *buf = msg->rx_buf;
>> +	u32 val;
>> +
>> +	/* Wait end of the read operation */
>> +	ret = readl_poll_timeout(dsi->base + DSI_CMD_PKT_STATUS,
>> +				 val, !(val & GEN_RD_CMD_BUSY),
>> +				 1000, CMD_PKT_STATUS_TIMEOUT_US);
>> +	if (ret) {
>> +		dev_err(dsi->dev, "Timeout during read operation\n");
>> +		return ret;
>> +	}
>> +
>> +	for (i = 0; i < len; i += 4) {
>> +		/* Read fifo must not be empty before all bytes are read */
>> +		ret = readl_poll_timeout(dsi->base + DSI_CMD_PKT_STATUS,
>> +					 val, !(val & GEN_PLD_R_EMPTY),
>> +					 1000, CMD_PKT_STATUS_TIMEOUT_US);
>> +		if (ret) {
>> +			dev_err(dsi->dev, "Read payload FIFO is empty\n");
>> +			return ret;
>> +		}
>> +
>> +		val = dsi_read(dsi, DSI_GEN_PLD_DATA);
>> +		for (j = 0; j < 4 && j + i < len; j++)
>> +			buf[i + j] = val >> (8 * j);
>> +	}
>> +
>> +	return ret;
>> +}
>> +
>>   static ssize_t dw_mipi_dsi_host_transfer(struct mipi_dsi_host *host,
>>   					 const struct mipi_dsi_msg *msg)
>>   {
>>   	struct dw_mipi_dsi *dsi = host_to_dsi(host);
>>   	struct mipi_dsi_packet packet;
>> -	int ret;
>> -
>> -	if (msg->rx_buf || msg->rx_len) {
>> -		/* TODO dw drv improvements: implement read feature */
>> -		dev_warn(dsi->dev, "read operations not yet implemented\n");
>> -		return -EINVAL;
>> -	}
>> +	int ret, nb_bytes;
>>   
>>   	ret = mipi_dsi_create_packet(&packet, msg);
>>   	if (ret) {
>> @@ -422,12 +450,16 @@ static ssize_t dw_mipi_dsi_host_transfer(struct mipi_dsi_host *host,
>>   	if (ret)
>>   		return ret;
>>   
>> -	/*
>> -	 * TODO Only transmitted size is returned as actual driver does
>> -	 * not support dcs/generic reads. Please update return value when
>> -	 * delivering the read feature.
>> -	 */
>> -	return packet.size;
>> +	if (msg->rx_buf && msg->rx_len) {
>> +		ret = dw_mipi_dsi_read(dsi, msg);
>> +		if (ret)
>> +			return ret;
>> +		nb_bytes = msg->rx_len;
>> +	} else {
>> +		nb_bytes = packet.size;
>> +	}
>> +
>> +	return nb_bytes;
>>   }
>>   
>>   static const struct mipi_dsi_host_ops dw_mipi_dsi_host_ops = {
> 
>