From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joseph Lo Subject: Re: [PATCH 2/8] clk: tegra: clock changes for emc scaling support on Tegra210 Date: Mon, 8 Apr 2019 15:52:37 +0800 Message-ID: <104f44ba-cd61-44a5-6c31-2b0af91c7b44@nvidia.com> References: <20190325074523.26456-1-josephl@nvidia.com> <20190325074523.26456-3-josephl@nvidia.com> <20190403092250.GG5238@ulmo> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190403092250.GG5238@ulmo> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Thierry Reding Cc: devicetree@vger.kernel.org, Stephen Boyd , Peter De Schrijver , Jonathan Hunter , Rob Herring , linux-tegra@vger.kernel.org, linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org List-Id: devicetree@vger.kernel.org On 4/3/19 5:22 PM, Thierry Reding wrote: > On Mon, Mar 25, 2019 at 03:45:17PM +0800, Joseph Lo wrote: >> 1) Introduce low jitter paths for pllp and pll_mb used by the EMC driver. >> 2) Remove the old emc_mux clock and don't use the common EMC clock >> definition. This will be replaced by a new clock defined in the EMC >> driver. >> 3) Export functions to allow accessing the CAR register required for EMC >> clock scaling. These functions will be used to access the CAR register >> as part of the scaling sequence. > > The fact that you can enumerate 3 logical changes made by this commit > indicates that it should be split up into smaller patches. Okay, will do. > >> Based on the work of Peter De Schrijver . >> >> Signed-off-by: Joseph Lo >> --- >> drivers/clk/tegra/clk-tegra210.c | 112 +++++++++++++++++++---- >> include/dt-bindings/clock/tegra210-car.h | 4 +- >> include/linux/clk/tegra.h | 5 + >> 3 files changed, 103 insertions(+), 18 deletions(-) >> >> diff --git a/drivers/clk/tegra/clk-tegra210.c b/drivers/clk/tegra/clk-tegra210.c >> index 7545af763d7a..e17b5279ea69 100644 >> --- a/drivers/clk/tegra/clk-tegra210.c >> +++ b/drivers/clk/tegra/clk-tegra210.c >> @@ -47,6 +47,7 @@ >> #define CLK_SOURCE_LA 0x1f8 >> #define CLK_SOURCE_SDMMC2 0x154 >> #define CLK_SOURCE_SDMMC4 0x164 >> +#define CLK_SOURCE_EMC_DLL 0x664 >> >> #define PLLC_BASE 0x80 >> #define PLLC_OUT 0x84 >> @@ -234,6 +235,10 @@ >> #define RST_DFLL_DVCO 0x2f4 >> #define DVFS_DFLL_RESET_SHIFT 0 >> >> +#define CLK_RST_CONTROLLER_CLK_OUT_ENB_X_SET 0x284 >> +#define CLK_RST_CONTROLLER_CLK_OUT_ENB_X_CLR 0x288 >> +#define CLK_OUT_ENB_X_CLK_ENB_EMC_DLL BIT(14) >> + >> #define CLK_RST_CONTROLLER_RST_DEV_Y_SET 0x2a8 >> #define CLK_RST_CONTROLLER_RST_DEV_Y_CLR 0x2ac >> >> @@ -319,12 +324,6 @@ static unsigned long tegra210_input_freq[] = { >> [8] = 12000000, >> }; >> >> -static const char *mux_pllmcp_clkm[] = { >> - "pll_m", "pll_c", "pll_p", "clk_m", "pll_m_ud", "pll_mb", "pll_mb", >> - "pll_p", >> -}; >> -#define mux_pllmcp_clkm_idx NULL >> - >> #define PLL_ENABLE (1 << 30) >> >> #define PLLCX_MISC1_IDDQ (1 << 27) >> @@ -2310,7 +2309,7 @@ static struct tegra_clk tegra210_clks[tegra_clk_max] __initdata = { >> [tegra_clk_i2c2] = { .dt_id = TEGRA210_CLK_I2C2, .present = true }, >> [tegra_clk_uartc_8] = { .dt_id = TEGRA210_CLK_UARTC, .present = true }, >> [tegra_clk_mipi_cal] = { .dt_id = TEGRA210_CLK_MIPI_CAL, .present = true }, >> - [tegra_clk_emc] = { .dt_id = TEGRA210_CLK_EMC, .present = true }, >> + [tegra_clk_emc] = { .dt_id = TEGRA210_CLK_EMC, .present = false }, >> [tegra_clk_usb2] = { .dt_id = TEGRA210_CLK_USB2, .present = true }, >> [tegra_clk_bsev] = { .dt_id = TEGRA210_CLK_BSEV, .present = true }, >> [tegra_clk_uartd_8] = { .dt_id = TEGRA210_CLK_UARTD, .present = true }, >> @@ -2921,6 +2920,82 @@ static int tegra210_init_pllu(void) >> return 0; >> } >> >> +void tegra210_clk_emc_dll_enable(bool flag) >> +{ >> + unsigned long flags = 0; >> + u32 offset = flag ? CLK_RST_CONTROLLER_CLK_OUT_ENB_X_SET : >> + CLK_RST_CONTROLLER_CLK_OUT_ENB_X_CLR; >> + >> + spin_lock_irqsave(&emc_lock, flags); >> + >> + writel_relaxed(CLK_OUT_ENB_X_CLK_ENB_EMC_DLL, clk_base + offset); >> + readl(clk_base + offset); >> + >> + spin_unlock_irqrestore(&emc_lock, flags); >> +} >> +EXPORT_SYMBOL_GPL(tegra210_clk_emc_dll_enable); >> + >> +void tegra210_clk_emc_dll_update_setting(u32 emc_dll_src_value) > > Do we really want to pass the whole register value through this > function? The register has three fields, so perhaps it's safer to pass > the fields individually? Or perhaps we only need to modify a subset of > the fields and can reduce the number of parameters we pass? Letting a > different driver pass any arbitrary value here takes away any means of > checking for validity. The emc table has a property for this register. So the scaling sequence will update the register with the value in the table. > >> +{ >> + unsigned long flags = 0; >> + >> + spin_lock_irqsave(&emc_lock, flags); >> + >> + writel_relaxed(emc_dll_src_value, clk_base + CLK_SOURCE_EMC_DLL); >> + readl(clk_base + CLK_SOURCE_EMC_DLL); > > Could we not just use a writel() here and do away with the flushing > readl()? Will try that. > > Also, it doesn't look like that spinlock actually protects anything. > You're just writing a value. If anyone else is holding that lock they > will either overwrite our value after we release the lock, or we > overwrite their value when they release the lock. Yeah, agreed. Will remove. Thanks, Joseph > >> + >> + spin_unlock_irqrestore(&emc_lock, flags); >> +} >> +EXPORT_SYMBOL_GPL(tegra210_clk_emc_dll_update_setting); >> + >> +void tegra210_clk_emc_update_setting(u32 emc_src_value) >> +{ >> + unsigned long flags = 0; >> + >> + spin_lock_irqsave(&emc_lock, flags); >> + >> + writel_relaxed(emc_src_value, clk_base + CLK_SOURCE_EMC); >> + readl(clk_base + CLK_SOURCE_EMC); >> + >> + spin_unlock_irqrestore(&emc_lock, flags); >> +} >> +EXPORT_SYMBOL_GPL(tegra210_clk_emc_update_setting); > > Same comments as above. > >> + >> +u32 tegra210_clk_emc_get_setting(void) >> +{ >> + unsigned long flags = 0; >> + u32 val; >> + >> + spin_lock_irqsave(&emc_lock, flags); >> + >> + val = readl_relaxed(clk_base + CLK_SOURCE_EMC); >> + >> + spin_unlock_irqrestore(&emc_lock, flags); > > Similar to the above, the spinlock doesn't protect anything here. > > Thierry >