Re: [PATCH RESEND v4 1/6] dmaengine: dw: Add peripheral bus width verification

Andy Shevchenko
2024-09-14T19:12:39Z

On Fri, Aug 02, 2024 at 10:50:46AM +0300, Serge Semin wrote:
> Currently the src_addr_width and dst_addr_width fields of the
> dma_slave_config structure are mapped to the CTLx.SRC_TR_WIDTH and
> CTLx.DST_TR_WIDTH fields of the peripheral bus side in order to have the
> properly aligned data passed to the target device. It's done just by
> converting the passed peripheral bus width to the encoded value using the
> __ffs() function. This implementation has several problematic sides:
>
> 1. __ffs() is undefined if no bit exist in the passed value. Thus if the
> specified addr-width is DMA_SLAVE_BUSWIDTH_UNDEFINED, __ffs() may return
> unexpected value depending on the platform-specific implementation.
>
> 2. DW AHB DMA-engine permits having the power-of-2 transfer width limited
> by the DMAH_Mk_HDATA_WIDTH IP-core synthesize parameter. Specifying
> bus-width out of that constraints scope will definitely cause unexpected
> result since the destination reg will be only partly touched than the
> client driver implied.
>
> Let's fix all of that by adding the peripheral bus width verification
> method and calling it in dwc_config() which is supposed to be executed
> before preparing any transfer. The new method will make sure that the
> passed source or destination address width is valid and if undefined then
> the driver will just fallback to the 1-byte width transfer.

This patch broke Intel Merrifield iDMA32 + SPI PXA2xx configuration to
me. Since it's first in the series and most likely the rest is
dependent and we are almost at the release date I propose to roll back
and start again after v6.12-rc1 will be out. Vinod, can we revert the
entire series, please?

--
With Best Regards,
Andy Shevchenko