From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shawn Lin Subject: Re: [PATCH 2/2] mmc: dw_mmc: add resets support to dw_mmc Date: Tue, 29 Mar 2016 14:09:32 +0800 Message-ID: <56FA1C1C.4090008@rock-chips.com> References: <1457254062-22677-1-git-send-email-guodong.xu@linaro.org> <1457254062-22677-2-git-send-email-guodong.xu@linaro.org> <56DC3BAD.8020107@rock-chips.com> <56F9E6E5.9000100@kernel-upstream.org> <56FA192A.9030209@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <56FA192A.9030209@samsung.com> Sender: linux-kernel-owner@vger.kernel.org To: Jaehoon Chung , Guodong Xu Cc: shawn.lin@rock-chips.com, robh+dt@kernel.org, =?UTF-8?Q?Pawe=c5=82_Moll?= , Mark Rutland , ijc+devicetree@hellion.org.uk, Kumar Gala , Ulf Hansson , devicetree@vger.kernel.org, "linux-kernel@vger.kernel.org" , linux-mmc@vger.kernel.org, Xinwei Kong , Zhangfei Gao List-Id: linux-mmc@vger.kernel.org =E5=9C=A8 2016/3/29 13:56, Jaehoon Chung =E5=86=99=E9=81=93: > On 03/29/2016 11:22 AM, Shawn Lin wrote: >> =E5=9C=A8 2016/3/25 13:35, Guodong Xu =E5=86=99=E9=81=93: >>> Hi, Shawn >>> >>> Sorry I replied late. I added comments below. >>> >>> On 6 March 2016 at 22:16, Shawn Lin >> > wrote: >>> >>> On 2016/3/6 16:47, Guodong Xu wrote: >>> >>> mmc registers may in abnormal state if mmc is used in boot= loader, >>> eg. to support booting from eMMC. So we need reset mmc reg= isters >>> when kernel boots up, instead of assuming mmc is in clean = state. >>> >>> With this patch, user can add a 'resets' property into dw_= mmc dts >>> node. When driver parse_dt and probe, it calls reset API t= o >>> deassert the 'reset' of dw_mmc host controller. When probe= error or >>> remove, it calls reset API to assert it. >>> >>> Please also refer to >>> Documentation/devicetree/bindings/reset/reset.txt >>> >>> Signed-off-by: Guodong Xu >> > >>> Signed-off-by: Xinwei Kong >> > >>> Signed-off-by: Zhangfei Gao >> > >>> >>> >>> Really should V2 and add the changelog. >>> >>> >>> Yes, will do. next version I sent will be labelled as V3. >>> >>> >>> >>> --- >>> drivers/mmc/host/dw_mmc.c | 22 +++++++++++++++++++++- >>> 1 file changed, 21 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/= dw_mmc.c >>> index 242f9a0..281ea9c 100644 >>> --- a/drivers/mmc/host/dw_mmc.c >>> +++ b/drivers/mmc/host/dw_mmc.c >>> @@ -2878,6 +2878,14 @@ static struct dw_mci_board >>> *dw_mci_parse_dt(struct dw_mci *host) >>> if (!pdata) >>> return ERR_PTR(-ENOMEM); >>> >>> + /* find reset controller when exist */ >>> + pdata->rstc =3D devm_reset_control_get_optional(de= v, NULL); >>> + if (IS_ERR(pdata->rstc)) { >>> + if (PTR_ERR(pdata->rstc) =3D=3D -EPROBE_DE= =46ER) >>> + return ERR_PTR(-EPROBE_DEFER); >>> + pdata->rstc =3D NULL; >>> >>> >>> maybe we can remove "pdata->rstc =3D NULL", and directly >>> use IS_ERR(..) for the following "if (host->pdata->rstc !=3D N= ULL)" >>> statement >>> >>> >>> Yes, will do. >>> I see your point, other lines in this file are using IS_ERR(!..), I= will >>> use this style too. >>> >>> + } >>> + >>> /* find out number of slots supported */ >>> of_property_read_u32(np, "num-slots", &pdata->num= _slots); >>> >>> @@ -2949,7 +2957,9 @@ int dw_mci_probe(struct dw_mci *host= ) >>> >>> if (!host->pdata) { >>> host->pdata =3D dw_mci_parse_dt(host); >>> - if (IS_ERR(host->pdata)) { >>> + if (PTR_ERR(host->pdata) =3D=3D -EPROBE_DE= =46ER) >>> + return -EPROBE_DEFER; >>> >>> >>> please fix the coding style here. >>> >>> >>> Do you mean to add additional {} for this 'if' , like this? >>> >>> + if (PTR_ERR(host->pdata) =3D=3D -EPROBE_DEFER)= { >>> + return -EPROBE_DEFER; >>> >>> + } >>> >>> I will add {}. >>> >>> >>> >>> + else if (IS_ERR(host->pdata)) { >>> dev_err(host->dev, "platform data= not >>> available\n"); >>> return -EINVAL; >>> } >>> @@ -3012,6 +3022,9 @@ int dw_mci_probe(struct dw_mci *host= ) >>> } >>> } >>> >>> + if (host->pdata->rstc !=3D NULL) >>> + reset_control_deassert(host->pdata->rstc); >>> + >>> >>> >>> sorry, I can't follow your intention here. Shouldn't it be som= ething >>> like "assert mmc -> may need delay -> deassert mmc". As your c= urrent >>> code, nothing happend right? >>> >>> >>> The chip exits from bootloader with this bit asserted. And when ent= ering >>> kernel, we only need to deassert. >>> >>> In my current code, the driver deassert mmc in _probe(), and assert= mmc >>> in _remove(). >> >> I catch your point. From the previous discussion, we add it to make = sure >> dw_mmc in good state after leaving bootloader to kernel. But My real= question is that you can assert it in bootloader, so you can also >> dessert it in bootloaer to make sure dw_mmc work fine when probing >> in kernel. In that way, we don't need this patch? > > Doesn't dw_mci_hw_reset work fine? I think that card should be reset = with MMC_CAP_HW_RESET. > Could you check this? > MMC_CAP_HW_RESET actually reset the mmc card, but Guodong means to reset the controller rather than mmc card :) > Best Regards, > Jaehoon Chung > >> >> More to think, Is it ok to match the behaviour of bootloader stage? >> My bootloader doesn't assert the reset pin of dw_mmc, so it seams if >> I want to fix you issue on kernel stage, I need a new round of >> assert->delay->deassert. >> >> >>> >>> >>> >>> setup_timer(&host->cmd11_timer, >>> dw_mci_cmd11_timer, (unsigned long)ho= st); >>> >>> @@ -3164,6 +3177,9 @@ err_dmaunmap: >>> if (host->use_dma && host->dma_ops->exit) >>> host->dma_ops->exit(host); >>> >>> + if (host->pdata->rstc !=3D NULL) >>> + reset_control_assert(host->pdata->rstc); >>> + >>> err_clk_ciu: >>> if (!IS_ERR(host->ciu_clk)) >>> clk_disable_unprepare(host->ciu_clk); >>> @@ -3196,11 +3212,15 @@ void dw_mci_remove(struct dw_mci *= host) >>> if (host->use_dma && host->dma_ops->exit) >>> host->dma_ops->exit(host); >>> >>> + if (host->pdata->rstc !=3D NULL) >>> + reset_control_assert(host->pdata->rstc); >>> + >>> if (!IS_ERR(host->ciu_clk)) >>> clk_disable_unprepare(host->ciu_clk); >>> >>> if (!IS_ERR(host->biu_clk)) >>> clk_disable_unprepare(host->biu_clk); >>> + >>> } >>> >>> >>> unnecessary new line here. >>> >>> >>> Will fix. >>> >>> -Guodong >>> >>> >>> EXPORT_SYMBOL(dw_mci_remove); >>> >>> >>> >>> >>> -- >>> Best Regards >>> Shawn Lin >>> >>> >> >> >> > > > > --=20 Best Regards Shawn Lin