linux-kernel - Re: [PATCH v3 08/13] tty: serial: qcom-geni-serial: refactor qcom_geni_serial_handle

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Date:   Thu, 24 Nov 2022 08:18:11 +0100
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Bartosz Golaszewski <brgl@...ev.pl>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Vinod Koul <vkoul@...nel.org>, Alex Elder <elder@...nel.org>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-serial@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v3 08/13] tty: serial: qcom-geni-serial: refactor
 qcom_geni_serial_handle_tx()

On 23. 11. 22, 12:07, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> 
> qcom_geni_serial_handle_tx() is pretty big, let's move the code that
> handles the actual writing of data to a separate function which makes
> sense in preparation for introducing a dma variant of handle_tx().
> 
> Let's also shuffle the code a bit, drop unneeded variables and use
> uart_xmit_advance() instead of handling tail->xmit manually.
> 
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> ---
>   drivers/tty/serial/qcom_geni_serial.c | 54 +++++++++++++--------------
>   1 file changed, 27 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
> index 68a1402fbe58..658b6d596f58 100644
> --- a/drivers/tty/serial/qcom_geni_serial.c
> +++ b/drivers/tty/serial/qcom_geni_serial.c
> @@ -704,19 +704,42 @@ static void qcom_geni_serial_start_rx(struct uart_port *uport)
>   	writel(irq_en, uport->membase + SE_GENI_M_IRQ_EN);
>   }

I know you just shuffle the code, but:

> +static void qcom_geni_serial_send_chunk_fifo(struct uart_port *uport,
> +					     unsigned int chunk)
> +{
> +	struct qcom_geni_serial_port *port = to_dev_port(uport);
> +	struct circ_buf *xmit = &uport->state->xmit;
> +	u8 buf[BYTES_PER_FIFO_WORD];
> +	size_t remaining = chunk;

Why size_t when the others are uints? Well, BYTES_PER_FIFO_WORD should 
be defined as 4U.

> +	unsigned int tx_bytes;
> +	int c;
> +
> +	while (remaining) {
> +		memset(buf, 0, sizeof(buf));
> +		tx_bytes = min_t(size_t, remaining, BYTES_PER_FIFO_WORD);

Then, no need for min_t.

> +
> +		for (c = 0; c < tx_bytes ; c++) {
> +			buf[c] = xmit->buf[xmit->tail];
> +			uart_xmit_advance(uport, 1);
> +		}
> +
> +		iowrite32_rep(uport->membase + SE_GENI_TX_FIFOn, buf, 1);

I wonder, why is _rep variant used to transfer a single word? Only to 
hide the cast?

thanks,
-- 
js
suse labs