Messages in this thread | | | From | Taniya Das <> | Subject | Re: [PATCH v6] clk: qcom: Add lpass clock controller driver for SDM845 | Date | Wed, 10 Oct 2018 11:42:27 +0530 |
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On 10/10/2018 2:22 AM, Stephen Boyd wrote: > Quoting Taniya Das (2018-10-09 10:26:38) >> Hello Stephen, >> >> On 10/8/2018 8:14 AM, Stephen Boyd wrote: >>> Quoting Taniya Das (2018-10-04 05:02:26) >>>> Add support for the lpass clock controller found on SDM845 based devices. >>>> This would allow lpass peripheral loader drivers to control the clocks to >>>> bring the subsystem out of reset. >>>> LPASS clocks present on the global clock controller would be registered >>>> with the clock framework based on the device tree flag. Also do not gate >>>> these clocks if they are left unused. >>> >>> Why not gate them? This statement states what the code is doing, not why >>> it's doing it which is the more crucial information that should be >>> described in the commit text. Also, please add a comment about it to the >>> code next to the flag. >>> >>> I am concerned that it doesn't make any sense though, so probably it >>> shouldn't be marked as CLK_IGNORE_UNUSED and it's papering over some >>> other larger bug that needs to be fixed. >>> >> >> It does not have any bug, it is just that to access these lpass >> registers we would need the GCC lpass registers to be enabled. I would >> update the same in the commit text. >> >> During clock late_init these clocks should not be accessed to check the >> clock status as they would result in unclocked access. The client would >> request these clocks in the correct order and it would not have any issue. >> > > That seems like the bug right there. If the LPASS registers can't be > accessed unless the clks in GCC are enabled then this driver needs to > turn the clks on before reading/writing registers. Marking the clks as > ignore unused is skipping around the real problem. >
If the driver requests for the clocks they would maintain the order. But if the clock late init call is invoked before the driver requests, there is no way I could manage this dependency, that is the only reason to mark them unused.
>> >>>> >>>> Signed-off-by: Taniya Das <tdas@codeaurora.org> >>>> --- >>>> diff --git a/drivers/clk/qcom/gcc-sdm845.c b/drivers/clk/qcom/gcc-sdm845.c >>>> index 08d593e..6379b8b 100644 >>>> --- a/drivers/clk/qcom/gcc-sdm845.c >>>> +++ b/drivers/clk/qcom/gcc-sdm845.c >>>> @@ -3583,6 +3611,13 @@ static int gcc_sdm845_probe(struct platform_device *pdev) >>>> if (ret) >>>> return ret; >>>> >>>> + if (!of_property_read_bool(pdev->dev.of_node, "qcom,lpass-protected")) { >>>> + gcc_sdm845_clocks[GCC_LPASS_Q6_AXI_CLK] = >>>> + &gcc_lpass_q6_axi_clk.clkr; >>>> + gcc_sdm845_clocks[GCC_LPASS_SWAY_CLK] = >>>> + &gcc_lpass_sway_clk.clkr; > > For all intents and purposes could we not just mark these two as > CLK_IS_CRITICAL and then let the LPASS turn these on and off when it > cares (does it ever do so)? Or even just turn them on once in probe here > with direct register writes and then not care anymore to touch them > again? Or do we need to turn these clks on again later on when the > subsystem crashes to read/write the registers and cycle the clks back on > and off? > >>>> + } >>>> + >>>> return qcom_cc_really_probe(pdev, &gcc_sdm845_desc, regmap); >>>> } >>>> >>>> diff --git a/drivers/clk/qcom/lpasscc-sdm845.c b/drivers/clk/qcom/lpasscc-sdm845.c >>>> new file mode 100644 >>>> index 0000000..f7b9b0f >>>> --- /dev/null >>>> +++ b/drivers/clk/qcom/lpasscc-sdm845.c >>>> + }, >>>> + }, >>>> +}; >>>> + >>>> +static int lpass_clocks_sdm845_probe(struct platform_device *pdev, int index, >>>> + const struct qcom_cc_desc *desc) >>>> +{ >>>> + struct regmap *regmap; >>>> + struct resource *res; >>>> + void __iomem *base; >>>> + >>>> + res = platform_get_resource(pdev, IORESOURCE_MEM, index); >>>> + base = devm_ioremap_resource(&pdev->dev, res); >>>> + if (IS_ERR(base)) >>>> + return PTR_ERR(base); >>>> + >>>> + regmap = devm_regmap_init_mmio(&pdev->dev, base, desc->config); >>>> + if (IS_ERR(regmap)) >>>> + return PTR_ERR(regmap); >>> >>> If this happens again in the future we should move this into the >>> common.c file and let qcom_cc_probe_index() exist. >>> >> >> Yes, I agree, could submit a patch to add the new function and then >> clean it up. > > Ok, but please don't do anything now because we don't care yet. >
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