On 2 March 2018 at 09:51, Ludovic BARRE <ludovic.barre@xxxxxx> wrote: > > > On 03/01/2018 11:44 AM, Ulf Hansson wrote: >> >> On 1 March 2018 at 10:57, Ludovic BARRE <ludovic.barre@xxxxxx> wrote: >>> >>> Hi Ulf >>> >>> On 03/01/2018 10:06 AM, Ulf Hansson wrote: >>>> >>>> >>>> Hi Ludovic, >>>> >>>> On 28 February 2018 at 16:47, Ludovic Barre <ludovic.Barre@xxxxxx> >>>> wrote: >>>>> >>>>> >>>>> From: Ludovic Barre <ludovic.barre@xxxxxx> >>>>> >>>>> This patch serie adds support of stm32 SDMMC controller. >>>>> stm32h7 is the first SoC to use stm32 SDMMC controller >>>>> (previous SoC had pl180 controller). >>>> >>>> >>>> >>>> I am a not convinced this isn't a new improved variant of the pl180. >>>> According to register layout and the code you submitted in patch2, >>>> there are great similarities to pl180 and the mmci driver. >>> >>> >>> >>> In fact, ST designers which created stm32-sdmmc hardware block from >>> scratch >>> are the same which have done the modifications on pl180 variant (stm32 >>> legacy f4, f7). >>> So some registers or bits name seem identical (or strongly inspirited) >>> but >>> the engine and features are different. >> >> >> Well, in that case, I assume the driver would also need work >> differently, but when looking at the code in patch2 this doesn't seem >> to be the case. >> > > I understand why you push to avoid drivers multiplication. But I'm > scared to squash 2 different hardware block which are their own roadmap > in the same drivers. I fear that it complicates the features management and > maintenance of this driver. It may require more work for you to upstream the code you need. You may even have to re-factor existing code in mmci before you can add your specific parts on top. However, whether it gets complicated or not, I think much depends on the quality of the code changes we make. Both sdhci and dw_mmc gives an idea of how we can deal with variant differences, in particular when variant changes are a bit bigger. In the mmci case, so far the controller that differs the most, is the qcom variant, which also has the built-in DMA support, similar to your new ST variant. Perhaps there is some code we can re-use around that. > > there are some difference: > -the stm32-sdmmc use an internal dma (stm32-sdmmc is master on the bus), > -idma alignment constraint. > -idma transfer mode single buffer, double buffer... (future evolution) > -need a command to stop transmission for data state machine > -same bit naming could have offset, mask width or set in different register. > => I will try to synthesis register difference in a document > -voltage switch sequence > -delay block: calibration, tunning (sdr104) > -reset line required > -the same feature have not the same impact, example ddr mode > stm32:no bypass clk, activated in clk register > pl180: clkreg_neg_edge_enable, activated in datactrl register, Doesn't sound like this couldn't be done, yes there are differences but not that much. Sure we may need re-work the core driver mmci code, maybe convert it to set of library function instead and invent a couple mmci specific callbacks. As I said, sdhci and dw_mmc already does it, so I am sure it can be done. > ... > > stm32-sdmmc is just at begining of its life cycle. Each revision of this > block increases the difference with pl180. Today, I've just push the minimal That's fine, this happens all the time to sdhci and dw_mmc variants. Again, if it works for them, it should work for mmci. > driver to start a request, but I've not yet send all features of this > revision like sdio, sdr104 support. After this revision there already are 2 > other revisions in the pipe (at short term). > > I am Out of Office with limited access to my e-mail till 2018 march 12th > I'll try to think about it on ski slope. euh, in fact no just ski and enjoy > ;-) Enjoy you skiing and let's talk more when you get back! [...] 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
