On 22 December 2017 at 09:13, Y.b. Lu <yangbo.lu@xxxxxxx> wrote: > Hi Uffe, > > >> -----Original Message----- >> From: Ulf Hansson [mailto:ulf.hansson@xxxxxxxxxx] >> Sent: 2017年11月16日 15:34 >> To: Yinbo Zhu <yinbo.zhu@xxxxxxx> >> Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>; Y.b. Lu <yangbo.lu@xxxxxxx>; >> linux-mmc@xxxxxxxxxxxxxxx >> Subject: Re: [PATCH v1] mmc: sdhci-of-esdhc: Workaround for reducing the >> maximum speed on ls1021atwr >> >> On 15 November 2017 at 10:01, <yinbo.zhu@xxxxxxx> wrote: >> > From: "yinbo.zhu" <yinbo.zhu@xxxxxxx> >> > >> > In SDHC high speed AC timing, the tshivkh parameter is defined as >> > input setup times:SDHC_CMD, SDHC_DATx, to SDHC_CLK. The value of the >> > tshivkh should be 2.5 ns considering the round trip delay, board/data >> > skew. >> > However, because of this erratum, it needs at least 4.1 ns. >> > >> > eSDHC cannot run at the maximum clock speed for the high speed mode, >> > or there is a limit on the length of the trace on the board for data, >> > command, and clock lines of the SDHC. >> > >> > Signed-off-by: yinbo.zhu <yinbo.zhu@xxxxxxx> >> > --- >> > drivers/mmc/host/sdhci-of-esdhc.c | 6 ++++++ >> > 1 file changed, 6 insertions(+) >> > >> > diff --git a/drivers/mmc/host/sdhci-of-esdhc.c >> > b/drivers/mmc/host/sdhci-of-esdhc.c >> > index 023c24bd0d94..2744dd58a573 100644 >> > --- a/drivers/mmc/host/sdhci-of-esdhc.c >> > +++ b/drivers/mmc/host/sdhci-of-esdhc.c >> > @@ -498,6 +498,12 @@ static void esdhc_of_set_clock(struct sdhci_host >> *host, unsigned int clock) >> > clock -= 5000000; >> > } >> > >> > + /* Workaround to reduce the clock frequency for ls1021a esdhc */ >> > + if (of_find_compatible_node(NULL, NULL, "fsl,ls1021a-esdhc")) >> > + { >> >> It's better to use the ->data pointer in the struct of_device_id for this kind of >> variant data. >> >> In ->probe() you then call of_match_device() and pick up the ->data pointer >> and assign it to your driver private data. >> >> Many drivers already do like this. Have a look at dw_mmc-exynos.c for >> example. >> > > [Y.b. Lu] How about using soc_device_match()? There is also .data member could be used in soc_device_attribute structure. > Use soc_device_match() in esdhc_init and get .data information into sdhci_esdhc structure which is private data. > Current incorrect host version register value fix-up for some platforms is using this method. I think you need to answer the question: is the problem SoC specific or device-variant specific. Depending on the answer, you should pick the correct solution. [...] Kind regards Uffe -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
