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Date: Thu, 5 Jul 2018 16:49:55 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Ludovic Barre <ludovic.Barre@...com>
Cc: Rob Herring <robh+dt@...nel.org>,
Maxime Coquelin <mcoquelin.stm32@...il.com>,
Alexandre Torgue <alexandre.torgue@...com>,
Gerald Baeza <gerald.baeza@...com>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
devicetree@...r.kernel.org,
"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>
Subject: Re: [PATCH 18/19] mmc: mmci: add specific clk/pwr procedure for stm32 sdmmc
On 12 June 2018 at 15:14, Ludovic Barre <ludovic.Barre@...com> wrote:
> From: Ludovic Barre <ludovic.barre@...com>
>
> This patch adds specific clock and power ios for stm32 sdmmc variant.
> power ios: stm32 dedicated procedure must be done to perform power
> off/on procedures. To power off, the sdmmc must be reset and set
> to power cycle state before to disabling vqmmc. This drives low
> SDMMC_D[7:0], SDMMC_CMD and SDMMC_CK to prevent the Card from
> being supplied through the signal lines.
> To power on, set the SDMMC in power-off SDMMC_D[7:0], SDMMC_CMD
> and SDMMC_CK are driven high. Then we can set the SDMMC to
> Power-on state.
>
> clock ios: specific bits behavior:
> -clock divider card_clk = mclk / (2 * clkdiv)
> -ddr activation
> -wide bus 1/4/8bits
> -bus speed
> -receive clock selection (in_ck/ck_in/fb_ck)
>
> Signed-off-by: Ludovic Barre <ludovic.barre@...com>
> ---
> drivers/mmc/host/mmci.c | 112 ++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 112 insertions(+)
>
> diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
> index 86aef4f..af27a0a 100644
> --- a/drivers/mmc/host/mmci.c
> +++ b/drivers/mmc/host/mmci.c
> @@ -50,6 +50,10 @@
>
> static unsigned int fmax = 515633;
>
> +static void mmci_sdmmc_set_pwrreg(struct mmci_host *host,
> + unsigned char power_mode, unsigned int pwr);
> +static void mmci_sdmmc_set_clkreg(struct mmci_host *host, unsigned int desired);
> +
> static struct variant_data variant_arm = {
> .fifosize = 16 * 4,
> .fifohalfsize = 8 * 4,
> @@ -490,6 +494,114 @@ static void mmci_set_pwrreg(struct mmci_host *host, unsigned char power_mode,
> mmci_write_pwrreg(host, pwr);
> }
>
> +static void mmci_sdmmc_set_clkreg(struct mmci_host *host, unsigned int desired)
> +{
> + unsigned int clk = 0, ddr = 0;
> +
> + if (host->mmc->ios.timing == MMC_TIMING_MMC_DDR52 ||
> + host->mmc->ios.timing == MMC_TIMING_UHS_DDR50)
> + ddr = MCI_STM32_CLK_DDR;
> +
> + /*
> + * cclk = mclk / (2 * clkdiv)
> + * clkdiv 0 => bypass
> + * in ddr mode bypass is not possible
> + */
> + if (desired) {
> + if (desired >= host->mclk && !ddr) {
> + host->cclk = host->mclk;
> + } else {
> + clk = DIV_ROUND_UP(host->mclk, 2 * desired);
> + if (clk > MCI_STM32_CLK_CLKDIV_MSK)
> + clk = MCI_STM32_CLK_CLKDIV_MSK;
> + host->cclk = host->mclk / (2 * clk);
> + }
> + }
> +
> + if (host->mmc->ios.bus_width == MMC_BUS_WIDTH_4)
> + clk |= MCI_STM32_CLK_WIDEBUS_4;
> + if (host->mmc->ios.bus_width == MMC_BUS_WIDTH_8)
> + clk |= MCI_STM32_CLK_WIDEBUS_8;
> +
> + clk |= MCI_STM32_CLK_HWFCEN;
> + clk |= host->clk_reg_add;
> + clk |= ddr;
> +
> + /*
> + * SDMMC_FBCK is selected when an external Delay Block is needed
> + * with SDR104.
> + */
> + if (host->mmc->ios.timing >= MMC_TIMING_UHS_SDR50) {
> + clk |= MCI_STM32_CLK_BUSSPEED;
> + if (host->mmc->ios.timing == MMC_TIMING_UHS_SDR104) {
> + clk &= ~MCI_STM32_CLK_SEL_MSK;
> + clk |= MCI_STM32_CLK_SELFBCK;
> + }
> + }
> +
> + mmci_write_clkreg(host, clk);
> +}
> +
> +static void mmci_sdmmc_set_pwrreg(struct mmci_host *host,
> + unsigned char power_mode, unsigned int pwr)
> +{
> + struct mmc_host *mmc = host->mmc;
> +
> + pwr |= host->pwr_reg_add;
> +
> + switch (power_mode) {
> + case MMC_POWER_OFF:
> + if (!IS_ERR(mmc->supply.vmmc))
> + mmc_regulator_set_ocr(mmc, mmc->supply.vmmc, 0);
> +
> + /* Only a reset could disable sdmmc */
> + reset_control_assert(host->rst);
> + udelay(2);
> + reset_control_deassert(host->rst);
Could you please elaborate on what goes on here. Do you need to
reset-the controller when powering off the card?
> +
> + /* default mask (probe) must be activated */
> + writel(MCI_IRQENABLE | host->variant->start_err,
> + host->base + MMCIMASK0);
The above seems like it could be made generic. There is no reason to
keep IRQs enabled when the card is powered off.
> +
> + /*
> + * Set the SDMMC in Power-cycle state before to disabling vqmmc.
> + * This will make that the SDMMC_D[7:0], SDMMC_CMD and SDMMC_CK
> + * are driven low, to prevent the Card from being supplied
> + * through the signal lines.
> + */
> + mmci_write_pwrreg(host, MCI_STM32_PWR_CYC | pwr);
> +
> + if (!IS_ERR(host->mmc->supply.vqmmc) && host->vqmmc_enabled) {
> + regulator_disable(host->mmc->supply.vqmmc);
> + host->vqmmc_enabled = false;
> + }
> + break;
> + case MMC_POWER_UP:
> + if (!IS_ERR(mmc->supply.vmmc))
> + mmc_regulator_set_ocr(mmc, mmc->supply.vmmc,
> + mmc->ios.vdd);
> + break;
> + case MMC_POWER_ON:
> + if (!IS_ERR(host->mmc->supply.vqmmc) && !host->vqmmc_enabled) {
> + if (regulator_enable(host->mmc->supply.vqmmc) < 0)
> + dev_err(mmc_dev(host->mmc),
> + "failed to enable vqmmc regulator\n");
> + else
> + host->vqmmc_enabled = true;
> + }
> +
> + /*
> + * After a power-cycle state, we must set the SDMMC in
> + * Power-off. The SDMMC_D[7:0], SDMMC_CMD and SDMMC_CK are
> + * driven high. Then we can set the SDMMC to Power-on state
> + */
> + mmci_write_pwrreg(host, MCI_PWR_OFF | pwr);
> + mdelay(1);
> + mmci_write_pwrreg(host, MCI_PWR_ON | pwr);
This looks odd. MMC_POWER_ON is the last power phase. For every single
additional ios change (timing, clock, etc), you will hit this piece of
code. In other words, there will be a mdelay(1) each time, which is
probably not needed.
> + break;
> + }
> +}
> +
> static void
> mmci_request_end(struct mmci_host *host, struct mmc_request *mrq)
> {
> --
> 2.7.4
>
Overall I am wondering if mmci_sdmmc_set_pwrreg() can be made generic
inside the common mmci ->set_ios() functions instead.
For example, the reset can be optional and checked with
if(!IS_ERR(host->rst)) - and the others can probably be conditional
based on a variant data.
What do you think?
Kind regards
Uffe
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