linux-kernel - Re: [PATCH] mmc: tegra: Use sdhci_pltfm_clk_get_max

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Message-ID: <CAPDyKFoip8gFssftJKzVHD9PAk+j=Z1CTo=0uY9cGASzW8VRJg@mail.gmail.com>
Date:   Mon, 2 Jul 2018 15:16:52 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Aapo Vienamo <avienamo@...dia.com>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        linux-tegra@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: tegra: Use sdhci_pltfm_clk_get_max_clock

On 4 June 2018 at 17:35, Aapo Vienamo <avienamo@...dia.com> wrote:
> The sdhci get_max_clock callback is set to sdhci_pltfm_clk_get_max_clock
> and tegra_sdhci_get_max_clock is removed. It appears that the
> shdci-tegra specific callback was originally introduced due to the
> requirement that the host clock has to be twice the bus clock on DDR50
> mode. As far as I can tell the only effect the removal has on DDR50 mode
> is in cases where the parent clock is unable to supply the requested
> clock rate, causing the DDR50 mode to run at a lower frequency.
> Currently the DDR50 mode isn't enabled on any of the SoCs and would also
> require configuring the SDHCI clock divider register to function
> properly.
>
> The problem with tegra_sdhci_get_max_clock is that it divides the clock
> rate by two and thus artificially limits the maximum frequency of faster
> signaling modes which don't have the host-bus frequency ratio requirement
> of DDR50 such as SDR104 and HS200. Furthermore, the call to
> clk_round_rate() may return an error which isn't handled by
> tegra_sdhci_get_max_clock.
>
> Signed-off-by: Aapo Vienamo <avienamo@...dia.com>

Thanks, applied for next!

Kind regards
Uffe

> ---
>  drivers/mmc/host/sdhci-tegra.c | 15 ++-------------
>  1 file changed, 2 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> index 970d38f6..c8745b5 100644
> --- a/drivers/mmc/host/sdhci-tegra.c
> +++ b/drivers/mmc/host/sdhci-tegra.c
> @@ -234,17 +234,6 @@ static void tegra_sdhci_set_uhs_signaling(struct sdhci_host *host,
>         sdhci_set_uhs_signaling(host, timing);
>  }
>
> -static unsigned int tegra_sdhci_get_max_clock(struct sdhci_host *host)
> -{
> -       struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> -
> -       /*
> -        * DDR modes require the host to run at double the card frequency, so
> -        * the maximum rate we can support is half of the module input clock.
> -        */
> -       return clk_round_rate(pltfm_host->clk, UINT_MAX) / 2;
> -}
> -
>  static void tegra_sdhci_set_tap(struct sdhci_host *host, unsigned int tap)
>  {
>         u32 reg;
> @@ -309,7 +298,7 @@ static const struct sdhci_ops tegra_sdhci_ops = {
>         .platform_execute_tuning = tegra_sdhci_execute_tuning,
>         .set_uhs_signaling = tegra_sdhci_set_uhs_signaling,
>         .voltage_switch = tegra_sdhci_voltage_switch,
> -       .get_max_clock = tegra_sdhci_get_max_clock,
> +       .get_max_clock = sdhci_pltfm_clk_get_max_clock,
>  };
>
>  static const struct sdhci_pltfm_data sdhci_tegra20_pdata = {
> @@ -357,7 +346,7 @@ static const struct sdhci_ops tegra114_sdhci_ops = {
>         .platform_execute_tuning = tegra_sdhci_execute_tuning,
>         .set_uhs_signaling = tegra_sdhci_set_uhs_signaling,
>         .voltage_switch = tegra_sdhci_voltage_switch,
> -       .get_max_clock = tegra_sdhci_get_max_clock,
> +       .get_max_clock = sdhci_pltfm_clk_get_max_clock,
>  };
>
>  static const struct sdhci_pltfm_data sdhci_tegra114_pdata = {
> --
> 2.7.4
>