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Thu, 14 Feb 2019 16:40:31 +0800 Received: from MTKCAS32.mediatek.inc (172.27.4.184) by mtkmbs03n1.mediatek.inc (172.21.101.181) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Thu, 14 Feb 2019 16:40:29 +0800 Received: from [10.17.3.153] (10.17.3.153) by MTKCAS32.mediatek.inc (172.27.4.170) with Microsoft SMTP Server id 15.0.1395.4 via Frontend Transport; Thu, 14 Feb 2019 16:40:28 +0800 Message-ID: <1550133628.16070.32.camel@mhfsdcap03> Subject: Re: [PATCH v1] mmc: mmc: Fix HS setting in mmc_hs400_to_hs200() From: Chaotian Jing To: Ulf Hansson CC: Matthias Brugger , Shawn Lin , Simon Horman , "Kyle Roeschley" , Hongjie Fang , Harish Jenny K N , "linux-mmc@vger.kernel.org" , Linux Kernel Mailing List , Linux ARM , , srv_heupstream , Adrian Hunter Date: Thu, 14 Feb 2019 16:40:28 +0800 In-Reply-To: References: <1550048812-29068-1-git-send-email-chaotian.jing@mediatek.com> <1550110458.16070.30.camel@mhfsdcap03> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit MIME-Version: 1.0 X-MTK: N Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2019-02-14 at 09:14 +0100, Ulf Hansson wrote: > On Thu, 14 Feb 2019 at 03:14, Chaotian Jing wrote: > > > > On Wed, 2019-02-13 at 13:08 +0100, Ulf Hansson wrote: > > > On Wed, 13 Feb 2019 at 10:07, Chaotian Jing wrote: > > > > > > > > mmc_hs400_to_hs200() begins with the card and host in HS400 mode. > > > > Therefore, any commands sent to the card should use HS400 timing. > > > > reduce clock frequency to 50Mhz but without host timming change > > > > may cause CMD6 response CRC error. because host still running at > > > > hs400 mode, and it's hard to find a suitable setting for all eMMC > > > > cards when clock frequency reduced to 50Mhz but card & host still > > > > in hs400 mode. > > > > this patch refers to mmc_select_hs400(), make the reduce clock frequency > > > > after card timing change. > > > > > > > > Signed-off-by: Chaotian Jing > > > > Fixes: ef3d232245ab ("mmc: mmc: Relax checking for switch errors after HS200 switch") > > > > --- > > > > drivers/mmc/core/mmc.c | 29 +++++++++++++++++++++++------ > > > > 1 file changed, 23 insertions(+), 6 deletions(-) > > > > > > > > diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c > > > > index 09c688f..00adc2d 100644 > > > > --- a/drivers/mmc/core/mmc.c > > > > +++ b/drivers/mmc/core/mmc.c > > > > @@ -1239,20 +1239,37 @@ int mmc_hs400_to_hs200(struct mmc_card *card) > > > > int err; > > > > u8 val; > > > > > > > > - /* Reduce frequency to HS */ > > > > - max_dtr = card->ext_csd.hs_max_dtr; > > > > - mmc_set_clock(host, max_dtr); > > > > - > > > > /* Switch HS400 to HS DDR */ > > > > val = EXT_CSD_TIMING_HS; > > > > err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL, EXT_CSD_HS_TIMING, > > > > val, card->ext_csd.generic_cmd6_time, 0, > > > > true, false, true); > > > > - if (err) > > > > - goto out_err; > > > > + /* > > > > + * as we are on the way to do re-tune, so if the CMD6 got response CRC > > > > + * error, do not treat it as error. > > > > + */ > > > > + if (err) { > > > > + if (err == -EILSEQ) { > > > > + /* > > > > + * card will busy after sending out response and host > > > > + * driver may not wait busy de-assert when get > > > > + * response CRC error. so just wait enough time to > > > > + * ensure card leave busy state. > > > > + */ > > > > + mmc_delay(card->ext_csd.generic_cmd6_time); > > > > + pr_debug("%s: %s switch to HS got CRC error\n", > > > > + mmc_hostname(host), __func__); > > > > + } else { > > > > + goto out_err; > > > > + } > > > > + } > > > > > > > > mmc_set_timing(host, MMC_TIMING_MMC_DDR52); > > > > > > > > + /* Reduce frequency to HS */ > > > > + max_dtr = card->ext_csd.hs_max_dtr; > > > > + mmc_set_clock(host, max_dtr); > > > > + > > > > > > What Adrian suggested was to not to move this part, but instead, only > > > allow CRC errors from the CMD6 as above. > > > > > > I guess it didn't work for you? > > > > > It should work for me. another issue is CMD6 will be sent 3 times at max > > Alright, let's give it a try then. > > > err = mmc_wait_for_cmd(host, &cmd, MMC_CMD_RETRIES); > > Yeah, that one have I thought about earlier as well. > > > > > if the first CMD6 got response CRC error, then Host driver must wait > > busy signal de-assert before send the next CMD6. > > > > So that it really make sense to issue CMD6(R1B) for 3 times ? if host > > driver did not handle the first CMD6 response CRC error and send second > > CMD6 directly, then this CMD6 will get timeout due to card still in busy > > state. > > I fully agree with you, I don't think it makes sense to retry - not > even for any CMD6, because of the busy signalling the card may raise > afterwards. > > Perhaps we should start with a simple oneliner patch, giving zero > instead of MMC_CMD_RETRIES to mmc_wait_for_cmd() and see how that > plays. > > Then on top we can add the special error handling of the CRC errors, > along the lines of what you suggest. > > Does it make sense? > Sure, I will upload a new patch to change the retry time from 3 to 0 along with this patch. > [...] > > Kind regards > Uffe