Re: [PATCH v2 3/6] spi: sun6i: add quirk for in-controller clock divider

Andre Przywara
2023-05-06T21:59:18Z

On Sat, 6 May 2023 10:30:11 +0300
Maksim Kiselev <bigunclemax@gmail.com> wrote:

> From: Icenowy Zheng <icenowy@aosc.io>
>
> Previously SPI controllers in Allwinner SoCs has a clock divider inside.
> However now the clock divider is removed and to set the transfer clock
> rate it's only needed to set the SPI module clock to the target value.
>
> Add a quirk for this kind of SPI controllers.
>
> Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
> ---
> drivers/spi/spi-sun6i.c | 68 +++++++++++++++++++++++------------------
> 1 file changed, 38 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
> index 01a01cd86db5..82523011a3a5 100644
> --- a/drivers/spi/spi-sun6i.c
> +++ b/drivers/spi/spi-sun6i.c
> @@ -87,6 +87,7 @@
>
> struct sun6i_spi_cfg {
> unsigned long fifo_depth;
> + bool has_clk_ctl;
> };
>
> struct sun6i_spi {
> @@ -260,7 +261,7 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
> struct spi_transfer *tfr)
> {
> struct sun6i_spi *sspi = spi_master_get_devdata(master);
> - unsigned int mclk_rate, div, div_cdr1, div_cdr2, timeout;
> + unsigned int div, div_cdr1, div_cdr2, timeout;
> unsigned int start, end, tx_time;
> unsigned int trig_level;
> unsigned int tx_len = 0, rx_len = 0;
> @@ -350,39 +351,44 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
>
> sun6i_spi_write(sspi, SUN6I_TFR_CTL_REG, reg);
>
> - /* Ensure that we have a parent clock fast enough */
> - mclk_rate = clk_get_rate(sspi->mclk);
> - if (mclk_rate < (2 * tfr->speed_hz)) {
> - clk_set_rate(sspi->mclk, 2 * tfr->speed_hz);
> - mclk_rate = clk_get_rate(sspi->mclk);
> - }
> + if (sspi->cfg->has_clk_ctl) {
> + unsigned int mclk_rate = clk_get_rate(sspi->mclk);

New line here please, to separate variable declaration from code.

> + /* Ensure that we have a parent clock fast enough */
> + if (mclk_rate < (2 * tfr->speed_hz)) {
> + clk_set_rate(sspi->mclk, 2 * tfr->speed_hz);
> + mclk_rate = clk_get_rate(sspi->mclk);
> + }
>
> - /*
> - * Setup clock divider.
> - *
> - * We have two choices there. Either we can use the clock
> - * divide rate 1, which is calculated thanks to this formula:
> - * SPI_CLK = MOD_CLK / (2 ^ cdr)
> - * Or we can use CDR2, which is calculated with the formula:
> - * SPI_CLK = MOD_CLK / (2 * (cdr + 1))
> - * Wether we use the former or the latter is set through the
> - * DRS bit.
> - *
> - * First try CDR2, and if we can't reach the expected
> - * frequency, fall back to CDR1.
> - */
> - div_cdr1 = DIV_ROUND_UP(mclk_rate, tfr->speed_hz);
> - div_cdr2 = DIV_ROUND_UP(div_cdr1, 2);
> - if (div_cdr2 <= (SUN6I_CLK_CTL_CDR2_MASK + 1)) {
> - reg = SUN6I_CLK_CTL_CDR2(div_cdr2 - 1) | SUN6I_CLK_CTL_DRS;
> - tfr->effective_speed_hz = mclk_rate / (2 * div_cdr2);
> + /*
> + * Setup clock divider.
> + *
> + * We have two choices there. Either we can use the clock
> + * divide rate 1, which is calculated thanks to this formula:
> + * SPI_CLK = MOD_CLK / (2 ^ cdr)
> + * Or we can use CDR2, which is calculated with the formula:
> + * SPI_CLK = MOD_CLK / (2 * (cdr + 1))
> + * Wether we use the former or the latter is set through the
> + * DRS bit.
> + *
> + * First try CDR2, and if we can't reach the expected
> + * frequency, fall back to CDR1.
> + */
> + div_cdr1 = DIV_ROUND_UP(mclk_rate, tfr->speed_hz);
> + div_cdr2 = DIV_ROUND_UP(div_cdr1, 2);
> + if (div_cdr2 <= (SUN6I_CLK_CTL_CDR2_MASK + 1)) {
> + reg = SUN6I_CLK_CTL_CDR2(div_cdr2 - 1) | SUN6I_CLK_CTL_DRS;
> + tfr->effective_speed_hz = mclk_rate / (2 * div_cdr2);
> + } else {
> + div = min(SUN6I_CLK_CTL_CDR1_MASK, order_base_2(div_cdr1));
> + reg = SUN6I_CLK_CTL_CDR1(div);
> + tfr->effective_speed_hz = mclk_rate / (1 << div);
> + }
> +
> + sun6i_spi_write(sspi, SUN6I_CLK_CTL_REG, reg);
> } else {
> - div = min(SUN6I_CLK_CTL_CDR1_MASK, order_base_2(div_cdr1));
> - reg = SUN6I_CLK_CTL_CDR1(div);
> - tfr->effective_speed_hz = mclk_rate / (1 << div);
> + clk_set_rate(sspi->mclk, tfr->speed_hz);

Don't we need to set tfr->effective_speed_hz to the actually programmed
clock rate here?

The rest looks fine, it's really mostly that old block indented.

Cheers,
Andre

> }
>
> - sun6i_spi_write(sspi, SUN6I_CLK_CTL_REG, reg);
> /* Finally enable the bus - doing so before might raise SCK to HIGH */
> reg = sun6i_spi_read(sspi, SUN6I_GBL_CTL_REG);
> reg |= SUN6I_GBL_CTL_BUS_ENABLE;
> @@ -701,10 +707,12 @@ static void sun6i_spi_remove(struct platform_device *pdev)
>
> static const struct sun6i_spi_cfg sun6i_a31_spi_cfg = {
> .fifo_depth = SUN6I_FIFO_DEPTH,
> + .has_clk_ctl = true,
> };
>
> static const struct sun6i_spi_cfg sun8i_h3_spi_cfg = {
> .fifo_depth = SUN8I_FIFO_DEPTH,
> + .has_clk_ctl = true,
> };
>
> static const struct of_device_id sun6i_spi_match[] = {